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Diffstat (limited to 'doc/system-operation.inc')
| -rw-r--r-- | doc/system-operation.inc | 404 |
1 files changed, 41 insertions, 363 deletions
diff --git a/doc/system-operation.inc b/doc/system-operation.inc index d7c56eaa..dd8d7d02 100644 --- a/doc/system-operation.inc +++ b/doc/system-operation.inc @@ -28,72 +28,6 @@ completes initialization and self test, and decides which mode to enter next. - Here's a short summary of all of the modes and the beeping (or - flashing, in the case of TeleMini v1) that accompanies each - mode. In the description of the beeping pattern, “dit” means a - short beep while "dah" means a long beep (three times as - long). “Brap” means a long dissonant tone. - - .AltOS Modes - [options="border",cols="1,1,2,2"] - |==== - |Mode Name - |Abbreviation - |Beeps - |Description - - |Startup - |S - |battery voltage in decivolts - |Calibrating sensors, detecting orientation. - - |Idle - |I - |dit dit - |Ready to accept commands over USB or radio link. - - |Pad - |P - |dit dah dah dit - |Waiting for launch. Not listening for commands. - - |Boost - |B - |dah dit dit dit - |Accelerating upwards. - - |Fast - |F - |dit dit dah dit - |Decelerating, but moving faster than 200m/s. - - |Coast - |C - |dah dit dah dit - |Decelerating, moving slower than 200m/s - - |Drogue - |D - |dah dit dit - |Descending after apogee. Above main height. - - |Main - |M - |dah dah - |Descending. Below main height. - - |Landed - |L - |dit dah dit dit - |Stable altitude for at least ten seconds. - - - |Sensor error - |X - |dah dit dit dah - |Error detected during sensor calibration. - |==== - In flight or “pad” mode, the altimeter engages the flight state machine, goes into transmit-only mode to send telemetry, and waits for launch to be detected. Flight mode is indicated @@ -317,308 +251,52 @@ === Radio Link - TeleMetrum, TeleMini and TeleMega all incorporate an RF transceiver, but - it's not a full duplex system... each end can only be transmitting or - receiving at any given moment. So we had to decide how to manage the + TeleMetrum, TeleMini and TeleMega all incorporate an + RF transceiver, but it's not a full duplex system; + each end can only be transmitting or receiving at any + given moment. So we had to decide how to manage the link. - By design, the altimeter firmware listens for the radio link when - it's in “idle mode”, which - allows us to use the radio link to configure the rocket, do things like - ejection tests, and extract data after a flight without having to - crack open the air-frame. However, when the board is in “flight - mode”, the altimeter only - transmits and doesn't listen at all. That's because we want to put - ultimate priority on event detection and getting telemetry out of - the rocket through - the radio in case the rocket crashes and we aren't able to extract - data later... - - We don't generally use a 'normal packet radio' mode like APRS - because they're just too inefficient. The GFSK modulation we - use is FSK with the base-band pulses passed through a Gaussian - filter before they go into the modulator to limit the - transmitted bandwidth. When combined with forward error - correction and interleaving, this allows us to have a very - robust 19.2 kilobit data link with only 10-40 milliwatts of - transmit power, a whip antenna in the rocket, and a hand-held - Yagi on the ground. We've had flights to above 21k feet AGL - with great reception, and calculations suggest we should be - good to well over 40k feet AGL with a 5-element yagi on the - ground with our 10mW units and over 100k feet AGL with the - 40mW devices. We hope to fly boards to higher altitudes over - time, and would of course appreciate customer feedback on - performance in higher altitude flights! - - === APRS - - TeleMetrum v2.0 and TeleMega can send APRS if desired, and the - interval between APRS packets can be configured. As each APRS - packet takes a full second to transmit, we recommend an - interval of at least 5 seconds to avoid consuming too much - battery power or radio channel bandwidth. You can configure - the APRS interval using AltosUI; that process is described in - the Configure Altimeter section of the AltosUI chapter. - - AltOS uses the APRS compressed position report data format, - which provides for higher position precision and shorter - packets than the original APRS format. It also includes - altitude data, which is invaluable when tracking rockets. We - haven't found a receiver which doesn't handle compressed - positions, but it's just possible that you have one, so if you - have an older device that can receive the raw packets but - isn't displaying position information, it's possible that this - is the cause. - - APRS packets include an SSID (Secondary Station Identifier) - field that allows one operator to have multiple - transmitters. AltOS allows you to set this to a single digit - from 0 to 9, allowing you to fly multiple transmitters at the - same time while keeping the identify of each one separate in - the receiver. By default, the SSID is set to the last digit of - the device serial number. - - The APRS packet format includes a comment field that can have - arbitrary text in it. AltOS uses this to send status - information about the flight computer. It sends four fields as - shown in the following table. - - .Altus Metrum APRS Comments - [options="header",cols="1,1,3"] - |==== - |Field |Example |Description - - |1 - |L - |GPS Status U for unlocked, L for locked - - |2 - |6 - |Number of Satellites in View - - |3 - |B4.0 - |Altimeter Battery Voltage - - |4 - |A3.7 - |Apogee Igniter Voltage - - |5 - |M3.7 - |Main Igniter Voltage - - |6 - |1286 - |Device Serial Number - |==== - - Here's an example of an APRS comment showing GPS lock with 6 - satellites in view, a primary battery at 4.0V, and - apogee and main igniters both at 3.7V from device 1286. - - .... - L6 B4.0 A3.7 M3.7 1286 - .... - - Make sure your primary battery is above 3.8V, any - connected igniters are above 3.5V and GPS is locked - with at least 5 or 6 satellites in view before - flying. If GPS is switching between L and U regularly, - then it doesn't have a good lock and you should wait - until it becomes stable. - - If the GPS receiver loses lock, the APRS data - transmitted will contain the last position for which - GPS lock was available. You can tell that this has - happened by noticing that the GPS status character - switches from 'L' to 'U'. Before GPS has locked, APRS - will transmit zero for latitude, longitude and - altitude. + By design, the altimeter firmware listens for the + radio link when it's in “idle mode”, which allows us + to use the radio link to configure the rocket, do + things like ejection tests, and extract data after a + flight without having to crack open the air-frame. + However, when the board is in “flight mode”, the + altimeter only transmits and doesn't listen at all. + That's because we want to put ultimate priority on + event detection and getting telemetry out of the + rocket through the radio in case the rocket crashes + and we aren't able to extract data later. + + We don't generally use a 'normal packet radio' mode + like APRS because they're just too inefficient. The + GFSK modulation we use is FSK with the base-band + pulses passed through a Gaussian filter before they go + into the modulator to limit the transmitted bandwidth. + When combined with forward error correction and + interleaving, this allows us to have a very robust + 19.2 kilobit data link with only 10-40 milliwatts of + transmit power, a whip antenna in the rocket, and a + hand-held Yagi on the ground. We've had flights to + above 21k feet AGL with great reception, and + calculations suggest we should be good to well over + 40k feet AGL with a 5-element yagi on the ground with + our 10mW units and over 100k feet AGL with the 40mW + devices. We hope to fly boards to higher altitudes + over time, and would of course appreciate customer + feedback on performance in higher altitude flights! + + :aprsdevices: TeleMetrum v2.0 and TeleMega + :configure_section: _configure_altimeter + include::aprs-operation.raw[] === Configurable Parameters Configuring an Altus Metrum altimeter for flight is very simple. Even on our baro-only TeleMini and EasyMini boards, the use of a Kalman filter means - there is no need to set a “mach delay”. The few - configurable parameters can all be set using AltosUI - over USB or or radio link via TeleDongle. Read the - Configure Altimeter section in the AltosUI chapter - below for more information. - - ==== Radio Frequency - - Altus Metrum boards support radio frequencies - in the 70cm band. By default, the - configuration interface provides a list of 10 - “standard” frequencies in 100kHz channels - starting at 434.550MHz. However, the firmware - supports use of any 50kHz multiple within the - 70cm band. At any given launch, we highly - recommend coordinating when and by whom each - frequency will be used to avoid interference. - And of course, both altimeter and TeleDongle - must be configured to the same frequency to - successfully communicate with each other. - - ==== Callsign - - This sets the callsign used for telemetry, - APRS and the packet link. For telemetry and - APRS, this is used to identify the device. For - the packet link, the callsign must match that - configured in AltosUI or the link will not - work. This is to prevent accidental - configuration of another Altus Metrum flight - computer operating on the same frequency - nearby. - - ==== Telemetry/RDF/APRS Enable - - You can completely disable the radio while in - flight, if necessary. This doesn't disable the - packet link in idle mode. - - ==== Telemetry baud rate - - This sets the modulation bit rate for data - transmission for both telemetry and packet - link mode. Lower bit rates will increase range - while reducing the amount of data that can be - sent and increasing battery consumption. All - telemetry is done using a rate 1/2 constraint - 4 convolution code, so the actual data - transmission rate is 1/2 of the modulation bit - rate specified here. - - ==== APRS Interval - - This selects how often APRS packets are - transmitted. Set this to zero to disable APRS - without also disabling the regular telemetry - and RDF transmissions. As APRS takes a full - second to transmit a single position report, - we recommend sending packets no more than once - every 5 seconds. - - ==== APRS SSID - - This selects the SSID reported in APRS - packets. By default, it is set to the last - digit of the serial number, but you can change - this to any value from 0 to 9. - - ==== Apogee Delay - - Apogee delay is the number of seconds after - the altimeter detects flight apogee that the - drogue charge should be fired. In most cases, - this should be left at the default of 0. - However, if you are flying redundant - electronics such as for an L3 certification, - you may wish to set one of your altimeters to - a positive delay so that both primary and - backup pyrotechnic charges do not fire - simultaneously. - - The Altus Metrum apogee detection algorithm - fires exactly at apogee. If you are also - flying an altimeter like the PerfectFlite - MAWD, which only supports selecting 0 or 1 - seconds of apogee delay, you may wish to set - the MAWD to 0 seconds delay and set the - TeleMetrum to fire your backup 2 or 3 seconds - later to avoid any chance of both charges - firing simultaneously. We've flown several - air-frames this way quite happily, including - Keith's successful L3 cert. - - ==== Apogee Lockout - - Apogee lockout is the number of seconds after - boost where the flight computer will not fire - the apogee charge, even if the rocket appears - to be at apogee. This is often called 'Mach - Delay', as it is intended to prevent a flight - computer from unintentionally firing apogee - charges due to the pressure spike that occurrs - across a mach transition. Altus Metrum flight - computers include a Kalman filter which is not - fooled by this sharp pressure increase, and so - this setting should be left at the default - value of zero to disable it. - - ==== Main Deployment Altitude - - By default, the altimeter will fire the main - deployment charge at an elevation of 250 - meters (about 820 feet) above ground. We - think this is a good elevation for most - air-frames, but feel free to change this to - suit. In particular, if you are flying two - altimeters, you may wish to set the deployment - elevation for the backup altimeter to be - something lower than the primary so that both - pyrotechnic charges don't fire simultaneously. - - ==== Maximum Flight Log - - Changing this value will set the maximum - amount of flight log storage that an - individual flight will use. The available - storage is divided into as many flights of the - specified size as can fit in the available - space. You can download and erase individual - flight logs. If you fill up the available - storage, future flights will not get logged - until you erase some of the stored ones. - - Even though our flight computers (except TeleMini v1.0) can store - multiple flights, we strongly recommend downloading and saving - flight data after each flight. - - ==== Ignite Mode - - Instead of firing one charge at apogee and - another charge at a fixed height above the - ground, you can configure the altimeter to - fire both at apogee or both during - descent. This was added to support an airframe - Bdale designed that had two altimeters, one in - the fin can and one in the nose. - - Providing the ability to use both igniters for - apogee or main allows some level of redundancy - without needing two flight computers. In - Redundant Apogee or Redundant Main mode, the - two charges will be fired two seconds apart. - - ==== Pad Orientation - - TeleMetrum, TeleMega and EasyMega measure - acceleration along the axis of the - board. Which way the board is oriented affects - the sign of the acceleration value. Instead of - trying to guess which way the board is mounted - in the air frame, the altimeter must be - explicitly configured for either Antenna Up or - Antenna Down. The default, Antenna Up, expects - the end of the board connected to the 70cm - antenna to be nearest the nose of the rocket, - with the end containing the screw terminals - nearest the tail. - - ==== Configurable Pyro Channels - - In addition to the usual Apogee and Main pyro - channels, TeleMega and EasyMega have four - additional channels that can be configured to - activate when various flight conditions are - satisfied. You can select as many conditions - as necessary; all of them must be met in order - to activate the channel. The conditions - available are: - - include::pyro-channels.raw[] - + there is no need to set a “mach delay”. All of the + configurable parameters can be set using AltosUI + over USB or or radio link via TeleDongle. Read + <<_configure_altimeter>> for more information. |