diff options
| author | Bdale Garbee <bdale@gag.com> | 2016-01-10 20:45:25 -0700 |
|---|---|---|
| committer | Bdale Garbee <bdale@gag.com> | 2016-01-10 20:45:25 -0700 |
| commit | 6409eee47a07294ec1a763f0a66d92ba47030b09 (patch) | |
| tree | 3ac66a2e710166ed9ff0cb2e782eb59b5f1291bd /AltOS/doc/micropeak.html | |
| parent | e2af81ee56c078040126dbff9183b4ee8563f1a6 (diff) | |
update docs
Diffstat (limited to 'AltOS/doc/micropeak.html')
| -rw-r--r-- | AltOS/doc/micropeak.html | 712 |
1 files changed, 326 insertions, 386 deletions
diff --git a/AltOS/doc/micropeak.html b/AltOS/doc/micropeak.html index 627266d..7347af3 100644 --- a/AltOS/doc/micropeak.html +++ b/AltOS/doc/micropeak.html @@ -1,386 +1,326 @@ -<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>MicroPeak Owner's Manual</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="book"><div class="titlepage"><div><div><h1 class="title"><a name="idm45460940730432"></a>MicroPeak Owner's Manual</h1></div><div><h2 class="subtitle">A recording altimeter for hobby rocketry</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Keith</span> <span class="surname">Packard</span></h3></div></div><div><p class="copyright">Copyright © 2014 Bdale Garbee and Keith Packard</p></div><div><div class="legalnotice"><a name="idm45460913524128"></a><p> - This document is released under the terms of the - <a class="ulink" href="http://creativecommons.org/licenses/by-sa/3.0/" target="_top"> - Creative Commons ShareAlike 3.0 - </a> - license. - </p></div></div><div><div class="revhistory"><table style="border-style:solid; width:100%;" summary="Revision History"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr><tr><td align="left">Revision 0.1</td><td align="left">29 October 2012</td></tr><tr><td align="left" colspan="2"> - Initial release with preliminary hardware. - </td></tr><tr><td align="left">Revision 1.0</td><td align="left">18 November 2012</td></tr><tr><td align="left" colspan="2"> - Updates for version 1.0 release. - </td></tr><tr><td align="left">Revision 1.1</td><td align="left">12 December 2012</td></tr><tr><td align="left" colspan="2"> - Add comments about EEPROM storage format and programming jig. - </td></tr><tr><td align="left">Revision 1.2</td><td align="left">20 January 2013</td></tr><tr><td align="left" colspan="2"> - Add documentation for the MicroPeak USB adapter board. Note - the switch to a Kalman filter for peak altitude - determination. - </td></tr><tr><td align="left">Revision 1.3.2</td><td align="left">12 February 2014</td></tr><tr><td align="left" colspan="2"> - Add a "Download" button to the main window, which makes it - quicker to access the download function. Update the data - download documentation to reflect the new MicroPeak USB - adapter design. Monitor data during download to let you see - if the USB connection is working at all by showing the - characters received from the MicroPeak USB adapter. - </td></tr></table></div></div></div><hr></div><div class="dedication"><div class="titlepage"><div><div><h1 class="title"><a name="idm45460913513696"></a>Acknowledgements</h1></div></div></div><p> - Thanks to John Lyngdal for suggesting that we build something like this. - </p><p> - Have fun using these products, and we hope to meet all of you - out on the rocket flight line somewhere. - </p><div class="literallayout"><p><br> -Bdale Garbee, KB0G<br> -NAR #87103, TRA #12201<br> -<br> -Keith Packard, KD7SQG<br> -NAR #88757, TRA #12200<br> - </p></div><p> - </p></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#idm45460913510944">1. Quick Start Guide</a></span></dt><dt><span class="chapter"><a href="#idm45460910009728">2. Handling Precautions</a></span></dt><dt><span class="chapter"><a href="#idm45460910005344">3. The MicroPeak USB adapter</a></span></dt><dd><dl><dt><span class="section"><a href="#idm45460914399696">1. Installing the MicroPeak software</a></span></dt><dt><span class="section"><a href="#idm45460914396608">2. Downloading Micro Peak data</a></span></dt><dt><span class="section"><a href="#idm45460914373472">3. Analyzing MicroPeak Data</a></span></dt><dd><dl><dt><span class="section"><a href="#idm45460914369984">3.1. MicroPeak Graphs</a></span></dt><dt><span class="section"><a href="#idm45460914366384">3.2. MicroPeak Flight Statistics</a></span></dt><dt><span class="section"><a href="#idm45460914362512">3.3. Raw Data</a></span></dt><dt><span class="section"><a href="#idm45460908884080">3.4. Configuring the Graph</a></span></dt></dl></dd><dt><span class="section"><a href="#idm45460908880544">4. Setting MicroPeak Preferences</a></span></dt></dl></dd><dt><span class="chapter"><a href="#idm45460908870560">4. Technical Information</a></span></dt><dd><dl><dt><span class="section"><a href="#idm45460908869888">1. Barometric Sensor</a></span></dt><dt><span class="section"><a href="#idm45460908867136">2. Micro-controller</a></span></dt><dt><span class="section"><a href="#idm45460908864784">3. Lithium Battery</a></span></dt><dt><span class="section"><a href="#idm45460908862000">4. Atmospheric Model</a></span></dt><dt><span class="section"><a href="#idm45460908859024">5. Mechanical Considerations</a></span></dt><dt><span class="section"><a href="#idm45460908856272">6. On-board data storage</a></span></dt><dt><span class="section"><a href="#idm45460908835936">7. MicroPeak Programming Interface</a></span></dt></dl></dd></dl></div><div class="list-of-tables"><p><b>List of Tables</b></p><dl><dt>4.1. <a href="#idm45460908854160">MicroPeak EEPROM Data Storage</a></dt></dl></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm45460913510944"></a>Chapter 1. Quick Start Guide</h1></div></div></div><p> - MicroPeak is designed to be easy to use. Requiring no external - components, flying takes just a few steps - </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> - Install the battery. Fit a CR1025 battery into the plastic - carrier. The positive (+) terminal should be towards the more - open side of the carrier. Slip the carrier into the battery - holder with the positive (+) terminal facing away from the - circuit board. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="405"><tr><td><img src="micropeak-back.jpg" width="405"></td></tr></table></div></div></li><li class="listitem"><p> - Install MicroPeak in your rocket. This can be as simple as - preparing a soft cushion of wadding inside a vented model payload - bay. Wherever you mount it, make sure you protect the - barometric sensor from corrosive ejection gasses as those - will damage the sensor, and shield it from light as that can - cause incorrect sensor readings. - </p></li><li class="listitem"><p> - Turn MicroPeak on. Slide the switch so that the actuator - covers the '1' printed on the board. MicroPeak will report - the maximum height of the last flight in decimeters using a - sequence of flashes on the LED. A sequence of short flashes - indicates one digit. A single long flash indicates zero. The - height is reported in decimeters, so the last digit will be - tenths of a meter. For example, if MicroPeak reports 5 4 4 - 3, then the maximum height of the last flight was 544.3m, or - 1786 feet. - </p></li><li class="listitem"><p> - Finish preparing the rocket for flight. After the - previous flight data have been reported, MicroPeak waits for - one minute before starting to check for launch. This gives - you time to finish assembling the rocket. As those - activities might cause pressure changes inside the airframe, - MicroPeak might accidentally detect boost. If you need to do - anything to the airframe after the one minute window passes, - make sure to be careful not to disturb the altimeter. The - LED will remain dark during the one minute delay, but after - that, it will start blinking once every 3 seconds. - </p></li><li class="listitem"><p> - Fly the rocket. Once the rocket passes about 30m in height - (100 feet), the micro-controller will record the ground - pressure and track the pressure seen during the flight. In - this mode, the LED flickers rapidly. When the rocket lands, - and the pressure stabilizes, the micro-controller will record - the minimum pressure pressure experienced during the flight, - compute the height represented by the difference in air - pressure and blink that value out on the LED. After that, - MicroPeak powers down to conserve battery power. - </p></li><li class="listitem"><p> - Recover the data. Turn MicroPeak off and then back on. MicroPeak - will blink out the maximum height for the last flight. Turn - MicroPeak back off to conserve battery power. - </p></li></ul></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm45460910009728"></a>Chapter 2. Handling Precautions</h1></div></div></div><p> - All Altus Metrum products are sophisticated electronic devices. - When handled gently and properly installed in an air-frame, they - will deliver impressive results. However, as with all electronic - devices, there are some precautions you must take. - </p><p> - The CR1025 Lithium batteries have an - extraordinary power density. This is great because we can fly with - much less battery mass... but if they are punctured - or their contacts are allowed to short, they can and will release their - energy very rapidly! - Thus we recommend that you take some care when handling MicroPeak - to keep conductive material from coming in contact with the exposed metal elements. - </p><p> - The barometric sensor used in MicroPeak is sensitive to - sunlight. Please consider this when designing an - installation. Many model rockets with payload bays use clear - plastic for the payload bay. Replacing these with an opaque - cardboard tube, painting them, or wrapping them with a layer of - masking tape are all reasonable approaches to keep the sensor - out of direct sunlight. - </p><p> - The barometric sensor sampling ports must be able to "breathe", - both by not being covered by foam or tape or other materials that might - directly block the hole on the top of the sensor, and also by having a - suitable static vent to outside air. - </p><p> - As with all other rocketry electronics, Altus Metrum altimeters must - be protected from exposure to corrosive motor exhaust and ejection - charge gasses. - </p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm45460910005344"></a>Chapter 3. The MicroPeak USB adapter</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm45460914399696">1. Installing the MicroPeak software</a></span></dt><dt><span class="section"><a href="#idm45460914396608">2. Downloading Micro Peak data</a></span></dt><dt><span class="section"><a href="#idm45460914373472">3. Analyzing MicroPeak Data</a></span></dt><dd><dl><dt><span class="section"><a href="#idm45460914369984">3.1. MicroPeak Graphs</a></span></dt><dt><span class="section"><a href="#idm45460914366384">3.2. MicroPeak Flight Statistics</a></span></dt><dt><span class="section"><a href="#idm45460914362512">3.3. Raw Data</a></span></dt><dt><span class="section"><a href="#idm45460908884080">3.4. Configuring the Graph</a></span></dt></dl></dd><dt><span class="section"><a href="#idm45460908880544">4. Setting MicroPeak Preferences</a></span></dt></dl></div><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="405"><tr><td><img src="MicroPeakUSB-2.0.jpg" width="405"></td></tr></table></div></div><p> - MicroPeak stores barometric pressure information for the first - 48 seconds of the flight in on-board non-volatile memory. The - contents of this memory can be downloaded to a computer using - the MicroPeak USB adapter. - </p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460914399696"></a>1. Installing the MicroPeak software</h2></div></div></div><p> - The MicroPeak application runs on Linux, Mac OS X and - Windows. You can download the latest version from - <a class="ulink" href="http://altusmetrum.org/AltOS" target="_top">http://altusmetrum.org/AltOS</a>. - </p><p> - On Mac OS X and Windows, the FTDI USB device driver needs to - be installed. A compatible version of this driver is included - with the MicroPeak application, but you may want to download a - newer version from <a class="ulink" href="http://www.ftdichip.com/FTDrivers.htm" target="_top">http://www.ftdichip.com/FTDrivers.htm</a>. - </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460914396608"></a>2. Downloading Micro Peak data</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> - Plug the MicroPeak USB adapter in to your computer. - </p></li><li class="listitem"><p> - Start the MicroPeak application. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="45"><tr><td><img src="micropeak-nofont.svg" width="45"></td></tr></table></div></div></li><li class="listitem"><p> - Click on the Download button at the top of the window. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="405"><tr><td><img src="micropeak-app.png" width="405"></td></tr></table></div></div></li><li class="listitem"><p> - Select from the listed devices. There will probably be - only one. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="207"><tr><td><img src="micropeak-device-dialog.png" width="207"></td></tr></table></div></div></li><li class="listitem"><p> - The application will now wait until it receives valid data - from the MicroPeak USB adapter. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="180"><tr><td><img src="micropeak-download.png" width="180"></td></tr></table></div></div><p> - The MicroPeak USB adapter has a small phototransistor - under the hole in the center of the box. - Locate this, turn on the MicroPeak and place the orange LED on the MicroPeak - directly inside the hole, resting the MicroPeak itself on - the box. You should see the blue LED on the MicroPeak USB - adapter blinking in time with the orange LED on the - MicroPeak board itself. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="405"><tr><td><img src="MicroPeakUSB-2.0-inuse.jpg" width="405"></td></tr></table></div></div></li><li class="listitem"><p> - After the maximum flight height is reported, MicroPeak will - pause for a few seconds, blink the LED four times rapidly - and then send the data in one long blur on the LED. The - MicroPeak application should receive the data. When it does, - it will present the data in a graph and offer to save the - data to a file. If not, you can power cycle the MicroPeak - board and try again. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="207"><tr><td><img src="micropeak-save-dialog.png" width="207"></td></tr></table></div></div></li><li class="listitem"><p> - Once the data are saved, a graph will be displayed with - height, speed and acceleration values computed from the - recorded barometric pressure data. See the next section - for more details on that. - </p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460914373472"></a>3. Analyzing MicroPeak Data</h2></div></div></div><p> - The MicroPeak application can present flight data in the form - of a graph, a collection of computed statistics or in tabular - form. - </p><p> - MicroPeak collects raw barometric pressure data which is - then used to compute the remaining data. Altitude is computed - through a standard atmospheric model. Absolute error in this - data will be affected by local atmospheric - conditions. Fortunately, these errors tend to mostly cancel - out, so the error in the height computation is much smaller - than the error in altitude would be. - </p><p> - Speed and acceleration are computed by first smoothing the - height data with a Gaussian window averaging filter. For speed - data, this average uses seven samples. For acceleration data, - eleven samples are used. These were chosen to provide - reasonably smooth speed and acceleration data, which would - otherwise be swamped with noise. - </p><p> - The File menu has operations to open existing flight logs, - Download new data from MicroPeak, Save a copy of the flight - log to a new file, Export the tabular data (as seen in the Raw - Data tab) to a file, change the application Preferences, Close - the current window or close all windows and Exit the - application. - </p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm45460914369984"></a>3.1. MicroPeak Graphs</h3></div></div></div><p> - Under the Graph tab, the height, speed and acceleration values - are displayed together. You can zoom in on the graph by - clicking and dragging to sweep out an area of - interest. Right-click on the plot to bring up a menu that will - let you save, copy or print the graph. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="405"><tr><td><img src="micropeak-graph.png" width="405"></td></tr></table></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm45460914366384"></a>3.2. MicroPeak Flight Statistics</h3></div></div></div><p> - The Statistics tab presents overall data from the flight. Note - that the Maximum height value is taken from the minumum - pressure captured in flight, and may be different from the - apparant apogee value as the on-board data are sampled twice - as fast as the recorded values, or because the true apogee - occurred after the on-board memory was full. Each value is - presented in several units as appropriate. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="405"><tr><td><img src="micropeak-statistics.png" width="405"></td></tr></table></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm45460914362512"></a>3.3. Raw Data</h3></div></div></div><p> - A table consisting of the both the raw barometric pressure - data and values computed from that for each recorded time. - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="405"><tr><td><img src="micropeak-raw-data.png" width="405"></td></tr></table></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm45460908884080"></a>3.4. Configuring the Graph</h3></div></div></div><p> - This selects which graph elements to show, and lets you - switch between metric and imperial units - </p><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="405"><tr><td><img src="micropeak-graph-configure.png" width="405"></td></tr></table></div></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460908880544"></a>4. Setting MicroPeak Preferences</h2></div></div></div><div class="informalfigure"><div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" style="cellpadding: 0; cellspacing: 0;" width="162"><tr><td><img src="micropeak-preferences.png" width="162"></td></tr></table></div></div><p> - The MicroPeak application has a few user settings which are - configured through the Preferences dialog, which can be - accessed from the File menu. - </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> - The Log Directory is where flight data will be saved to - and loaded from by default. Of course, you can always - navigate to other directories in the file chooser windows, - this setting is just the starting point. - </p></li><li class="listitem"><p> - If you prefer to see your graph data in feet and - miles per hour instead of meters and meters per second, - you can select Imperial Units. - </p></li><li class="listitem"><p> - To see what data is actually arriving over the serial - port, start the MicroPeak application from a command - prompt and select the Serial Debug option. This can be - useful in debugging serial communication problems, but - most people need never choose this. - </p></li><li class="listitem"><p> - You can adjust the size of the text in the Statistics tab - by changing the Font size preference. There are three - settings, with luck one will both fit on your screen and - provide readable values. - </p></li><li class="listitem"><p> - The Look & feel menu shows a list of available - application appearance choices. By default, the MicroPeak - application tries to blend in with other applications, but - you may choose some other appearance if you like. - </p></li></ul></div><p> - </p><p> - Note that MicroPeak shares a subset of the AltosUI - preferences, so if you use both of these applications, change - in one application will affect the other. - </p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm45460908870560"></a>Chapter 4. Technical Information</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm45460908869888">1. Barometric Sensor</a></span></dt><dt><span class="section"><a href="#idm45460908867136">2. Micro-controller</a></span></dt><dt><span class="section"><a href="#idm45460908864784">3. Lithium Battery</a></span></dt><dt><span class="section"><a href="#idm45460908862000">4. Atmospheric Model</a></span></dt><dt><span class="section"><a href="#idm45460908859024">5. Mechanical Considerations</a></span></dt><dt><span class="section"><a href="#idm45460908856272">6. On-board data storage</a></span></dt><dt><span class="section"><a href="#idm45460908835936">7. MicroPeak Programming Interface</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460908869888"></a>1. Barometric Sensor</h2></div></div></div><p> - MicroPeak uses the Measurement Specialties MS5607 sensor. This - has a range of 120kPa to 1kPa with an absolute accuracy of - 150Pa and a resolution of 2.4Pa. - </p><p> - The pressure range corresponds roughly to an altitude range of - -1500m (-4900 feet) to 31000m (102000 feet), while the - resolution is approximately 20cm (8 inches) near sea level and - 60cm (24in) at 10000m (33000 feet). - </p><p> - Ground pressure is computed from an average of 16 samples, - taken while the altimeter is at rest. The flight pressure used to - report maximum height is computed from a Kalman filter - designed to smooth out any minor noise in the sensor - values. The flight pressure recorded to non-volatile storage - is unfiltered, coming directly from the pressure sensor. - </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460908867136"></a>2. Micro-controller</h2></div></div></div><p> - MicroPeak uses an Atmel ATtiny85 micro-controller. This tiny - CPU contains 8kB of flash for the application, 512B of RAM for - temporary data storage and 512B of EEPROM for non-volatile - storage of previous flight data. - </p><p> - The ATtiny85 has a low-power mode which turns off all of the - clocks and powers down most of the internal components. In - this mode, the chip consumes only .1μA of power. MicroPeak - uses this mode once the flight has ended to preserve battery - power. - </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460908864784"></a>3. Lithium Battery</h2></div></div></div><p> - The CR1025 battery used by MicroPeak holds 30mAh of power, - which is sufficient to run for over 40 hours. Because - MicroPeak powers down on landing, run time includes only time - sitting on the launch pad or during flight. - </p><p> - The large positive terminal (+) is usually marked, while the - smaller negative terminal is not. Make sure you install the - battery with the positive terminal facing away from the - circuit board where it will be in contact with the metal - battery holder. A small pad on the circuit board makes contact - with the negative battery terminal. - </p><p> - Shipping restrictions may prevent us from including a CR1025 - battery with MicroPeak. If so, many stores carry CR1025 - batteries as they are commonly used in small electronic - devices such as flash lights. - </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460908862000"></a>4. Atmospheric Model</h2></div></div></div><p> - MicroPeak contains a fixed atmospheric model which is used to - convert barometric pressure into altitude. The model was - converted into a 469-element piece-wise linear approximation - which is then used to compute the altitude of the ground and - apogee. The difference between these represents the maximum - height of the flight. - </p><p> - The model assumes a particular set of atmospheric conditions, - which, while a reasonable average, cannot represent the changing - nature of the real atmosphere. Fortunately, for flights - reasonably close to the ground, the effect of this global - inaccuracy are largely canceled out when the computed ground - altitude is subtracted from the computed apogee altitude, so - the resulting height is more accurate than either the ground - or apogee altitudes. - </p><p> - Because the raw pressure data is recorded to non-volatile - storage, you can use that, along with a more sophisticated - atmospheric model, to compute your own altitude values. - </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460908859024"></a>5. Mechanical Considerations</h2></div></div></div><p> - MicroPeak is designed to be rugged enough for typical rocketry - applications. It contains two moving parts, the battery holder - and the power switch, which were selected for their - ruggedness. - </p><p> - The MicroPeak battery holder is designed to withstand impact - up to 150g without breaking contact (or, worse yet, causing - the battery to fall out). That means it should stand up to - almost any launch you care to try, and should withstand fairly - rough landings. - </p><p> - The power switch is designed to withstand up to 50g forces in - any direction. Because it is a sliding switch, orienting the - switch perpendicular to the direction of rocket travel will - serve to further protect the switch from launch forces. - </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460908856272"></a>6. On-board data storage</h2></div></div></div><p> - The ATtiny85 has 512 bytes of non-volatile storage, separate - from the code storage memory. The MicroPeak firmware uses this - to store information about the last completed - flight. Barometric measurements from the ground before launch - and at apogee are stored, and used at power-on to compute the - height of the last flight. - </p><p> - In addition to the data used to present the height of the last - flight, MicroPeak also stores barometric information sampled - at regular intervals during the flight. This is the - information captured with the MicroPeak USB adapter. It can - also be read from MicroPeak through any AVR programming - tool. - </p><div class="table"><a name="idm45460908854160"></a><p class="title"><b>Table 4.1. MicroPeak EEPROM Data Storage</b></p><div class="table-contents"><table summary="MicroPeak EEPROM Data Storage" border="1"><colgroup><col align="center" class="Address"><col align="center" class="Size (bytes)"><col align="left" class="Description"></colgroup><thead><tr><th align="center">Address</th><th align="center">Size (bytes)</th><th align="center">Description</th></tr></thead><tbody><tr><td align="center">0x000</td><td align="center">4</td><td align="left">Average ground pressure (Pa)</td></tr><tr><td align="center">0x004</td><td align="center">4</td><td align="left">Minimum flight pressure (Pa)</td></tr><tr><td align="center">0x008</td><td align="center">2</td><td align="left">Number of in-flight samples</td></tr><tr><td align="center">0x00a … 0x1fe</td><td align="center">2</td><td align="left">Instantaneous flight pressure (Pa) low 16 bits</td></tr></tbody></table></div></div><br class="table-break"><p> - All EEPROM data are stored least-significant byte first. The - instantaneous flight pressure data are stored without the - upper 16 bits of data. The upper bits can be reconstructed - from the previous sample, assuming that pressure doesn't - change by more more than 32kPa in a single sample - interval. Note that this pressure data is <span class="emphasis"><em>not</em></span> - filtered in any way, while both the recorded ground and apogee - pressure values are, so you shouldn't expect the minimum - instantaneous pressure value to match the recorded minimum - pressure value exactly. - </p><p> - MicroPeak samples pressure every 96ms, but stores only every - other sample in the EEPROM. This provides for 251 pressure - samples at 192ms intervals, or 48.192s of storage. The clock - used for these samples is a factory calibrated RC circuit - built into the ATtiny85 and is accurate only to within ±10% at - 25°C. So, you can count on the pressure data being accurate, - but speed or acceleration data computed from this will be - limited by the accuracy of this clock. - </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm45460908835936"></a>7. MicroPeak Programming Interface</h2></div></div></div><p> - MicroPeak exposes a standard 6-pin AVR programming interface, - but not using the usual 2x3 array of pins on 0.1" - centers. Instead, there is a single row of tiny 0.60mm × - 0.85mm pads on 1.20mm centers exposed near the edge of the - circuit board. We couldn't find any connector that was - small enough to include on the circuit board. - </p><p> - In lieu of an actual connector, the easiest way to connect to - the bare pads is through a set of Pogo pins. These - spring-loaded contacts are designed to connect in precisely - this way. We've designed a programming jig, the MicroPeak - Pogo Pin board which provides a standard AVR interface on one - end and a recessed slot for MicroPeak to align the board with - the Pogo Pins. - </p><p> - The MicroPeak Pogo Pin board is not a complete AVR programmer, - it is an interface board that provides a 3.3V regulated power - supply to run the MicroPeak via USB and a standard 6-pin AVR - programming interface with the usual 2x3 grid of pins on 0.1" - centers. This can be connected to any AVR programming - dongle. - </p><p> - The AVR programming interface cannot run faster than ¼ of the - AVR CPU clock frequency. Because MicroPeak runs at 250kHz to - save power, you must configure your AVR programming system to - clock the AVR programming interface at no faster than - 62.5kHz, or a clock period of 32µS. - </p></div></div></div></body></html> +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>MicroPeak Owner’s Manual</title><link rel="stylesheet" type="text/css" href="am.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /></head><body><div xml:lang="en" class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a id="idm46222414925680"></a>MicroPeak Owner’s Manual</h1></div><div><h2 class="subtitle">A recording altimeter for hobby rocketry</h2></div><div><h3 class="corpauthor"> + <span class="inlinemediaobject"><img src="micropeak-oneline.svg" width="270" /></span> +</h3></div><div><div class="author"><h3 class="author"><span class="firstname">Keith</span> <span class="surname">Packard</span></h3><code class="email"><<a class="email" href="mailto:keithp@keithp.com">keithp@keithp.com</a>></code></div></div><div><p class="copyright">Copyright © 2014 Keith Packard</p></div><div><div class="legalnotice"><a id="idm46222415052400"></a><p> + This document is released under the terms of the + <a class="ulink" href="http://creativecommons.org/licenses/by-sa/3.0/" target="_top"> + Creative Commons ShareAlike 3.0 + </a> + license. + </p></div></div><div><a href="micropeak-revhistory.html">Revision History</a></div></div><hr /></div><div class="dedication"><div class="titlepage"><div><div><h1 class="title"><a id="_acknowledgements"></a>Acknowledgements</h1></div></div></div><p>Thanks to John Lyngdal for suggesting that we build something +like this.</p><p>Have fun using these products, and we hope to meet all of you +out on the rocket flight line somewhere.</p><div class="blockquote"><blockquote class="blockquote"><div class="literallayout"><p>Bdale Garbee, KB0G<br /> +NAR #87103, TRA #12201</p></div></blockquote></div><div class="blockquote"><blockquote class="blockquote"><div class="literallayout"><p>Keith Packard, KD7SQG<br /> +NAR #88757, TRA #12200</p></div></blockquote></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="chapter"><a href="#_using_micropeak">1. Using MicroPeak</a></span></dt><dt><span class="chapter"><a href="#_the_micropeak_usb_adapter">2. The MicroPeak USB adapter</a></span></dt><dd><dl><dt><span class="section"><a href="#_installing_the_micropeak_software">2.1. Installing the MicroPeak software</a></span></dt><dt><span class="section"><a href="#_downloading_micro_peak_data">2.2. Downloading Micro Peak data</a></span></dt><dt><span class="section"><a href="#_analyzing_micropeak_data">2.3. Analyzing MicroPeak Data</a></span></dt><dd><dl><dt><span class="section"><a href="#_micropeak_graphs">2.3.1. MicroPeak Graphs</a></span></dt><dt><span class="section"><a href="#_micropeak_flight_statistics">2.3.2. MicroPeak Flight Statistics</a></span></dt><dt><span class="section"><a href="#_raw_flight_data">2.3.3. Raw Flight Data</a></span></dt><dt><span class="section"><a href="#_configuring_the_graph">2.3.4. Configuring the Graph</a></span></dt></dl></dd><dt><span class="section"><a href="#_setting_micropeak_preferences">2.4. Setting MicroPeak Preferences</a></span></dt></dl></dd><dt><span class="appendix"><a href="#_handling_precautions">A. Handling Precautions</a></span></dt><dt><span class="appendix"><a href="#_technical_information">B. Technical Information</a></span></dt><dd><dl><dt><span class="section"><a href="#_barometric_sensor">B.1. Barometric Sensor</a></span></dt><dt><span class="section"><a href="#_micro_controller">B.2. Micro-controller</a></span></dt><dt><span class="section"><a href="#_lithium_battery">B.3. Lithium Battery</a></span></dt><dt><span class="section"><a href="#_atmospheric_model">B.4. Atmospheric Model</a></span></dt><dt><span class="section"><a href="#_mechanical_considerations">B.5. Mechanical Considerations</a></span></dt><dt><span class="section"><a href="#_micropeak_programming_interface">B.6. MicroPeak Programming Interface</a></span></dt></dl></dd><dt><span class="appendix"><a href="#_on_board_data_storage">C. On-board data storage</a></span></dt></dl></div><div class="list-of-figures"><p><strong>List of Figures</strong></p><dl><dt>1.1. <a href="#idm46222411271328">MicroPeak and Battery</a></dt><dt>2.1. <a href="#idm46222414185232">MicroPeak USB Adapter</a></dt><dt>2.2. <a href="#idm46222415015888">MicroPeak Application</a></dt><dt>2.3. <a href="#idm46222415011264">MicroPeak Device Dialog</a></dt><dt>2.4. <a href="#idm46222415074064">MicroPeak Download Dialog</a></dt><dt>2.5. <a href="#idm46222415069120">MicroPeak Downloading</a></dt><dt>2.6. <a href="#idm46222415064112">MicroPeak Save Dialog</a></dt><dt>2.7. <a href="#idm46222409546800">MicroPeak Graph</a></dt><dt>2.8. <a href="#idm46222409541696">MicroPeak Flight Statistics</a></dt><dt>2.9. <a href="#idm46222409536688">MicroPeak Raw Flight Data</a></dt><dt>2.10. <a href="#idm46222409531904">MicroPeak Graph Configuration</a></dt><dt>2.11. <a href="#idm46222409527040">MicroPeak Preferences</a></dt></dl></div><div class="list-of-tables"><p><strong>List of Tables</strong></p><dl><dt>C.1. <a href="#idm46222409481536">MicroPeak EEPROM Data Storage</a></dt></dl></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="_using_micropeak"></a>Chapter 1. Using MicroPeak</h1></div></div></div><p>MicroPeak is designed to be easy to use. Requiring no external +components, flying takes just a few steps</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"> +Install the battery +</span></dt><dd> +Fit a CR1025 battery into the plastic carrier. The positive +(+) terminal should be towards the more open side of the +carrier. Slip the carrier into the battery holder with the +positive (+) terminal facing away from the circuit board. +</dd></dl></div><div class="figure"><a id="idm46222411271328"></a><p class="title"><strong>Figure 1.1. MicroPeak and Battery</strong></p><div class="figure-contents"><div class="mediaobject"><img src="micropeak-back.jpg" width="405" alt="micropeak-back.jpg" /></div></div></div><br class="figure-break" /><div class="variablelist"><dl class="variablelist"><dt><span class="term"> +Install MicroPeak in your rocket +</span></dt><dd> +This can be as simple as preparing a soft cushion of wadding +inside a vented model payload bay. Wherever you mount it, +make sure you protect the barometric sensor from corrosive +ejection gasses as those will damage the sensor, and shield +it from light as that can cause incorrect sensor readings. +</dd><dt><span class="term"> +Turn MicroPeak on +</span></dt><dd> +Slide the switch so that the actuator covers the <span class="emphasis"><em>1</em></span> printed +on the board. MicroPeak will report the maximum height of +the last flight in decimeters using a sequence of flashes on +the LED. A sequence of short flashes indicates one digit. A +single long flash indicates zero. The height is reported in +decimeters, so the last digit will be tenths of a meter. For +example, if MicroPeak reports 5 4 4 3, then the maximum +height of the last flight was 544.3m, or 1786 feet. +</dd><dt><span class="term"> +Finish preparing the rocket for flight +</span></dt><dd> +After the previous flight data have been reported, MicroPeak +waits for one minute before starting to check for +launch. This gives you time to finish assembling the +rocket. As those activities might cause pressure changes +inside the airframe, MicroPeak might accidentally detect +boost. If you need to do anything to the airframe after the +one minute window passes, make sure to be careful not to +disturb the altimeter. The LED will remain dark during the +one minute delay, but after that, it will start blinking +once every 3 seconds. +</dd><dt><span class="term"> +Fly the rocket +</span></dt><dd> +Once the rocket passes about 30m in height (100 feet), the +micro-controller will record the ground pressure and track +the pressure seen during the flight. In this mode, the LED +flickers rapidly. When the rocket lands, and the pressure +stabilizes, the micro-controller will record the minimum +pressure pressure experienced during the flight, compute the +height represented by the difference in air pressure and +blink that value out on the LED. After that, MicroPeak +powers down to conserve battery power. +</dd><dt><span class="term"> +Recover the data +</span></dt><dd> +Turn MicroPeak off and then back on. MicroPeak will blink +out the maximum height for the last flight. Turn MicroPeak +back off to conserve battery power. +</dd></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="_the_micropeak_usb_adapter"></a>Chapter 2. The MicroPeak USB adapter</h1></div></div></div><div class="figure"><a id="idm46222414185232"></a><p class="title"><strong>Figure 2.1. MicroPeak USB Adapter</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="MicroPeakUSB-2.0.jpg" align="middle" width="405" alt="MicroPeakUSB-2.0.jpg" /></div></div></div><br class="figure-break" /><p>MicroPeak stores barometric pressure information for the first +48 seconds of the flight in on-board non-volatile memory. The +contents of this memory can be downloaded to a computer using +the MicroPeak USB adapter.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_installing_the_micropeak_software"></a>2.1. Installing the MicroPeak software</h2></div></div></div><p>The MicroPeak application runs on Linux, Mac OS X and +Windows. You can download the latest version from +<a class="ulink" href="http://altusmetrum.org/MicroPeak" target="_top">http://altusmetrum.org/MicroPeak</a></p><p>On Mac OS X and Windows, the FTDI USB device driver +needs to be installed. A compatible version of this +driver is included with the MicroPeak application, but +you may want to download a newer version from +<a class="ulink" href="http://www.ftdichip.com/FTDrivers.htm" target="_top">http://www.ftdichip.com/FTDrivers.htm</a></p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_downloading_micro_peak_data"></a>2.2. Downloading Micro Peak data</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> +Plug the MicroPeak USB adapter in to your computer. +</li><li class="listitem"> +Start the MicroPeak application. +</li></ul></div><div class="informalfigure"><div class="mediaobject" align="center"><img src="micropeak-nofont.svg" align="middle" width="45" alt="micropeak-nofont.svg" /></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> +Click on the Download button at the top of the +window. +</li></ul></div><div class="figure"><a id="idm46222415015888"></a><p class="title"><strong>Figure 2.2. MicroPeak Application</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="micropeak-app.png" align="middle" width="405" alt="micropeak-app.png" /></div></div></div><br class="figure-break" /><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> +Select from the listed devices. There will probably +be only one. +</li></ul></div><div class="figure"><a id="idm46222415011264"></a><p class="title"><strong>Figure 2.3. MicroPeak Device Dialog</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="micropeak-device-dialog.png" align="middle" width="207" alt="micropeak-device-dialog.png" /></div></div></div><br class="figure-break" /><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> +The application will now wait until it receives +valid data from the MicroPeak USB adapter. +</li></ul></div><div class="figure"><a id="idm46222415074064"></a><p class="title"><strong>Figure 2.4. MicroPeak Download Dialog</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="micropeak-download.png" align="middle" width="180" alt="micropeak-download.png" /></div></div></div><br class="figure-break" /><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> +The MicroPeak USB adapter has a small +phototransistor under the hole in the center of the +box. Locate this, turn on the MicroPeak and place +the orange LED on the MicroPeak directly inside the +hole, resting the MicroPeak itself on the box. You +should see the blue LED on the MicroPeak USB adapter +blinking in time with the orange LED on the +MicroPeak board itself. +</li></ul></div><div class="figure"><a id="idm46222415069120"></a><p class="title"><strong>Figure 2.5. MicroPeak Downloading</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="MicroPeakUSB-2.0-inuse.jpg" align="middle" width="405" alt="MicroPeakUSB-2.0-inuse.jpg" /></div></div></div><br class="figure-break" /><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> +After the maximum flight height is reported, +MicroPeak will pause for a few seconds, blink the +LED four times rapidly and then send the data in one +long blur on the LED. The MicroPeak application +should receive the data. When it does, it will +present the data in a graph and offer to save the +data to a file. If not, you can power cycle the +MicroPeak board and try again. +</li></ul></div><div class="figure"><a id="idm46222415064112"></a><p class="title"><strong>Figure 2.6. MicroPeak Save Dialog</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="micropeak-save-dialog.png" align="middle" width="207" alt="micropeak-save-dialog.png" /></div></div></div><br class="figure-break" /><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> +Once the data are saved, a graph will be displayed +with height, speed and acceleration values computed +from the recorded barometric pressure data. See +<<_analyzing_micropeak_data> for more details on that. +</li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_analyzing_micropeak_data"></a>2.3. Analyzing MicroPeak Data</h2></div></div></div><p>The MicroPeak application can present flight data in +the form of a graph, a collection of computed +statistics or in tabular form.</p><p>MicroPeak collects raw barometric pressure data which +is then used to compute the remaining data. Altitude +is computed through a standard atmospheric +model. Absolute error in this data will be affected by +local atmospheric conditions. Fortunately, these +errors tend to mostly cancel out, so the error in the +height computation is much smaller than the error in +altitude would be.</p><p>Speed and acceleration are computed by first smoothing +the height data with a Gaussian window averaging +filter. For speed data, this average uses seven +samples. For acceleration data, eleven samples are +used. These were chosen to provide reasonably smooth +speed and acceleration data, which would otherwise be +swamped with noise.</p><p>The File menu has operations to open existing flight +logs, Download new data from MicroPeak, Save a copy of +the flight log to a new file, Export the tabular data +(as seen in the Raw Data tab) to a file, change the +application Preferences, Close the current window or +close all windows and Exit the application.</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="_micropeak_graphs"></a>2.3.1. MicroPeak Graphs</h3></div></div></div><div class="figure"><a id="idm46222409546800"></a><p class="title"><strong>Figure 2.7. MicroPeak Graph</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="micropeak-graph.png" align="middle" width="405" alt="micropeak-graph.png" /></div></div></div><br class="figure-break" /><p>Under the Graph tab, the height, speed and acceleration values +are displayed together. You can zoom in on the graph by +clicking and dragging to sweep out an area of +interest. Right-click on the plot to bring up a menu that will +let you save, copy or print the graph.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="_micropeak_flight_statistics"></a>2.3.2. MicroPeak Flight Statistics</h3></div></div></div><div class="figure"><a id="idm46222409541696"></a><p class="title"><strong>Figure 2.8. MicroPeak Flight Statistics</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="micropeak-statistics.png" align="middle" width="405" alt="micropeak-statistics.png" /></div></div></div><br class="figure-break" /><p>The Statistics tab presents overall data from +the flight. Note that the Maximum height value +is taken from the minumum pressure captured in +flight, and may be different from the apparant +apogee value as the on-board data are sampled +twice as fast as the recorded values, or +because the true apogee occurred after the +on-board memory was full. Each value is +presented in several units as appropriate.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="_raw_flight_data"></a>2.3.3. Raw Flight Data</h3></div></div></div><div class="figure"><a id="idm46222409536688"></a><p class="title"><strong>Figure 2.9. MicroPeak Raw Flight Data</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="micropeak-raw-data.png" align="middle" width="405" alt="micropeak-raw-data.png" /></div></div></div><br class="figure-break" /><p>A table consisting of the both the raw barometric pressure +data and values computed from that for each recorded time.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="_configuring_the_graph"></a>2.3.4. Configuring the Graph</h3></div></div></div><div class="figure"><a id="idm46222409531904"></a><p class="title"><strong>Figure 2.10. MicroPeak Graph Configuration</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="micropeak-graph-configure.png" align="middle" width="405" alt="micropeak-graph-configure.png" /></div></div></div><br class="figure-break" /><p>This selects which graph elements to show, and lets you +switch between metric and imperial units</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_setting_micropeak_preferences"></a>2.4. Setting MicroPeak Preferences</h2></div></div></div><div class="figure"><a id="idm46222409527040"></a><p class="title"><strong>Figure 2.11. MicroPeak Preferences</strong></p><div class="figure-contents"><div class="mediaobject" align="center"><img src="micropeak-preferences.png" align="middle" width="162" alt="micropeak-preferences.png" /></div></div></div><br class="figure-break" /><p>The MicroPeak application has a few user settings which are +configured through the Preferences dialog, which can be +accessed from the File menu.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"> +Log Directory +</span></dt><dd> +The Log Directory is where flight data will be +saved to and loaded from by default. Of +course, you can always navigate to other +directories in the file chooser windows, this +setting is just the starting point. +</dd><dt><span class="term"> +Imperial Units +</span></dt><dd> +If you prefer to see your graph data in feet +and miles per hour instead of meters and +meters per second, you can select Imperial +Units. +</dd><dt><span class="term"> +Serial Debug +</span></dt><dd> +To see what data is actually arriving over the +serial port, start the MicroPeak application +from a command prompt and select the Serial +Debug option. This can be useful in debugging +serial communication problems, but most people +need never choose this. +</dd><dt><span class="term"> +Font Size +</span></dt><dd> +You can adjust the size of the text in the +Statistics tab by changing the Font size +preference. There are three settings, with +luck one will both fit on your screen and +provide readable values. +</dd><dt><span class="term"> +Look & Feel +</span></dt><dd> +The Look & feel menu shows a list of available +application appearance choices. By default, +the MicroPeak application tries to blend in +with other applications, but you may choose +some other appearance if you like. +</dd></dl></div><p>Note that MicroPeak shares a subset of the +AltosUI preferences, so if you use both of +these applications, change in one application +will affect the other.</p></div></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="_handling_precautions"></a>Appendix A. Handling Precautions</h1></div></div></div><p>All Altus Metrum products are sophisticated electronic +devices. When handled gently and properly installed in an +air-frame, they will deliver impressive results. However, as +with all electronic devices, there are some precautions you +must take.</p><div class="warning" style="margin-left: 0; margin-right: 10%;"><h3 class="title">Warning</h3><p>The CR1025 Lithium batteries have an extraordinary power +density. This is great because we can fly with much less +battery mass… but if they are punctured or their contacts +are allowed to short, they can and will release their energy +very rapidly! Thus we recommend that you take some care when +handling MicroPeak to keep conductive material from coming in +contact with the exposed metal elements.</p></div><p>The barometric sensor used in MicroPeak is sensitive to +sunlight. Please consider this when designing an +installation. Many model rockets with payload bays use clear +plastic for the payload bay. Replacing these with an opaque +cardboard tube, painting them, or wrapping them with a layer +of masking tape are all reasonable approaches to keep the +sensor out of direct sunlight.</p><p>The barometric sensor sampling ports must be able to +"breathe", both by not being covered by foam or tape or other +materials that might directly block the hole on the top of the +sensor, and also by having a suitable static vent to outside +air.</p><p>As with all other rocketry electronics, Altus Metrum +altimeters must be protected from exposure to corrosive motor +exhaust and ejection charge gasses.</p></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="_technical_information"></a>Appendix B. Technical Information</h1></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_barometric_sensor"></a>B.1. Barometric Sensor</h2></div></div></div><p>MicroPeak uses the Measurement Specialties MS5607 +sensor. This has a range of 120kPa to 1kPa with an +absolute accuracy of 150Pa and a resolution of 2.4Pa.</p><p>The pressure range corresponds roughly to an altitude +range of -1500m (-4900 feet) to 31000m (102000 feet), +while the resolution is approximately 20cm (8 inches) +near sea level and 60cm (24in) at 10000m (33000 feet).</p><p>Ground pressure is computed from an average of 16 +samples, taken while the altimeter is at rest. The +flight pressure used to report maximum height is +computed from a Kalman filter designed to smooth out +any minor noise in the sensor values. The flight +pressure recorded to non-volatile storage is +unfiltered, coming directly from the pressure sensor.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_micro_controller"></a>B.2. Micro-controller</h2></div></div></div><p>MicroPeak uses an Atmel ATtiny85 +micro-controller. This tiny CPU contains 8kB of flash +for the application, 512B of RAM for temporary data +storage and 512B of EEPROM for non-volatile storage of +previous flight data.</p><p>The ATtiny85 has a low-power mode which turns off all +of the clocks and powers down most of the internal +components. In this mode, the chip consumes only .1μA +of power. MicroPeak uses this mode once the flight has +ended to preserve battery power.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_lithium_battery"></a>B.3. Lithium Battery</h2></div></div></div><p>The CR1025 battery used by MicroPeak holds 30mAh of +power, which is sufficient to run for over 40 +hours. Because MicroPeak powers down on landing, run +time includes only time sitting on the launch pad or +during flight.</p><p>The large positive terminal (+) is usually marked, +while the smaller negative terminal is not. Make sure +you install the battery with the positive terminal +facing away from the circuit board where it will be in +contact with the metal battery holder. A small pad on +the circuit board makes contact with the negative +battery terminal.</p><p>Shipping restrictions may prevent us from including a +CR1025 battery with MicroPeak. If so, many stores +carry CR1025 batteries as they are commonly used in +small electronic devices such as flash lights.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_atmospheric_model"></a>B.4. Atmospheric Model</h2></div></div></div><p>MicroPeak contains a fixed atmospheric model which is +used to convert barometric pressure into altitude. The +model was converted into a 469-element piece-wise +linear approximation which is then used to compute the +altitude of the ground and apogee. The difference +between these represents the maximum height of the +flight.</p><p>The model assumes a particular set of atmospheric +conditions, which, while a reasonable average, cannot +represent the changing nature of the real +atmosphere. Fortunately, for flights reasonably close +to the ground, the effect of this global inaccuracy +are largely canceled out when the computed ground +altitude is subtracted from the computed apogee +altitude, so the resulting height is more accurate +than either the ground or apogee altitudes.</p><p>Because the raw pressure data is recorded to +non-volatile storage, you can use that, along with a +more sophisticated atmospheric model, to compute your +own altitude values.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_mechanical_considerations"></a>B.5. Mechanical Considerations</h2></div></div></div><p>MicroPeak is designed to be rugged enough for typical +rocketry applications. It contains two moving parts, +the battery holder and the power switch, which were +selected for their ruggedness.</p><p>The MicroPeak battery holder is designed to withstand +impact up to 150g without breaking contact (or, worse +yet, causing the battery to fall out). That means it +should stand up to almost any launch you care to try, +and should withstand fairly rough landings.</p><p>The power switch is designed to withstand up to 50g +forces in any direction. Because it is a sliding +switch, orienting the switch perpendicular to the +direction of rocket travel will serve to further +protect the switch from launch forces.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_micropeak_programming_interface"></a>B.6. MicroPeak Programming Interface</h2></div></div></div><p>MicroPeak exposes a standard 6-pin AVR programming +interface, but not using the usual 2x3 array of pins +on 0.1" centers. Instead, there is a single row of +tiny 0.60mm × 0.85mm pads on 1.20mm centers exposed +near the edge of the circuit board. We couldn’t find +any connector that was small enough to include on the +circuit board.</p><p>In lieu of an actual connector, the easiest way to +connect to the bare pads is through a set of Pogo +pins. These spring-loaded contacts are designed to +connect in precisely this way. We’ve designed a +programming jig, the MicroPeak Pogo Pin board which +provides a standard AVR interface on one end and a +recessed slot for MicroPeak to align the board with +the Pogo Pins.</p><p>The MicroPeak Pogo Pin board is not a complete AVR +programmer, it is an interface board that provides a +3.3V regulated power supply to run the MicroPeak via +USB and a standard 6-pin AVR programming interface +with the usual 2x3 grid of pins on 0.1" centers. This +can be connected to any AVR programming dongle.</p><p>The AVR programming interface cannot run faster than ¼ +of the AVR CPU clock frequency. Because MicroPeak runs +at 250kHz to save power, you must configure your AVR +programming system to clock the AVR programming +interface at no faster than 62.5kHz, or a clock period +of 32µS.</p></div></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="_on_board_data_storage"></a>Appendix C. On-board data storage</h1></div></div></div><p>The ATtiny85 has 512 bytes of non-volatile storage, separate +from the code storage memory. The MicroPeak firmware uses this +to store information about the last completed +flight. Barometric measurements from the ground before launch +and at apogee are stored, and used at power-on to compute the +height of the last flight.</p><p>In addition to the data used to present the height of the last +flight, MicroPeak also stores barometric information sampled +at regular intervals during the flight. This is the +information captured with the MicroPeak USB adapter. It can +also be read from MicroPeak through any AVR programming tool.</p><div class="table"><a id="idm46222409481536"></a><p class="title"><strong>Table C.1. MicroPeak EEPROM Data Storage</strong></p><div class="table-contents"><table summary="MicroPeak EEPROM Data Storage" cellpadding="4px" style="border-collapse: collapse;border-top: 1px solid #78079a; border-bottom: 1px solid #78079a; border-left: 1px solid #78079a; border-right: 1px solid #78079a; "><colgroup><col class="col_1" /><col class="col_2" /><col class="col_3" /></colgroup><tbody><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Address</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Size (bytes)</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Description</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>0x000</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>4</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Average ground pressure (Pa)</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>0x004</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>4</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Minimum flight pressure (Pa)</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>0x008</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>2</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Number of in-flight samples</p></td></tr><tr><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p>0x00a … 0x1fe</p></td><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p>2</p></td><td style="" align="left" valign="top"><p>Instantaneous flight pressure (Pa) low 16 bits</p></td></tr></tbody></table></div></div><br class="table-break" /><p>All EEPROM data are stored least-significant byte first. The +instantaneous flight pressure data are stored without the +upper 16 bits of data. The upper bits can be reconstructed +from the previous sample, assuming that pressure doesn’t +change by more more than 32kPa in a single sample +interval. Note that this pressure data is <span class="strong"><strong>not</strong></span> filtered in +any way, while both the recorded ground and apogee pressure +values are, so you shouldn’t expect the minimum instantaneous +pressure value to match the recorded minimum pressure value +exactly.</p><p>MicroPeak samples pressure every 96ms, but stores only every +other sample in the EEPROM. This provides for 251 pressure +samples at 192ms intervals, or 48.192s of storage. The clock +used for these samples is a factory calibrated RC circuit +built into the ATtiny85 and is accurate only to within ±10% at +25°C. So, you can count on the pressure data being accurate, +but speed or acceleration data computed from this will be +limited by the accuracy of this clock.</p></div></div></body></html>
\ No newline at end of file |