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| -rw-r--r-- | doc/telemetrum.xsl | 123 |
1 files changed, 79 insertions, 44 deletions
diff --git a/doc/telemetrum.xsl b/doc/telemetrum.xsl index 6e4320e1..70a78693 100644 --- a/doc/telemetrum.xsl +++ b/doc/telemetrum.xsl @@ -61,64 +61,63 @@ </chapter> <chapter> <title>Specifications</title> - <itemizedlist> <listitem> - <para> - Recording altimeter for model rocketry. - </para> + <para> + Recording altimeter for model rocketry. + </para> </listitem> <listitem> - <para> - Supports dual deployment (can fire 2 ejection charges). - </para> + <para> + Supports dual deployment (can fire 2 ejection charges). + </para> </listitem> <listitem> - <para> - 70cm ham-band transceiver for telemetry downlink. - </para> + <para> + 70cm ham-band transceiver for telemetry downlink. + </para> </listitem> <listitem> - <para> - Barometric pressure sensor good to 45k feet MSL. - </para> + <para> + Barometric pressure sensor good to 45k feet MSL. + </para> </listitem> <listitem> - <para> - 1-axis high-g accelerometer for motor characterization, capable of - +/- 50g using default part. - </para> + <para> + 1-axis high-g accelerometer for motor characterization, capable of + +/- 50g using default part. + </para> </listitem> <listitem> - <para> - On-board, integrated GPS receiver with 5hz update rate capability. - </para> + <para> + On-board, integrated GPS receiver with 5hz update rate capability. + </para> </listitem> <listitem> - <para> - On-board 1 megabyte non-volatile memory for flight data storage. - </para> + <para> + On-board 1 megabyte non-volatile memory for flight data storage. + </para> </listitem> <listitem> - <para> - USB interface for battery charging, configuration, and data recovery. - </para> + <para> + USB interface for battery charging, configuration, and data recovery. + </para> </listitem> <listitem> - <para> - Fully integrated support for LiPo rechargeable batteries. - </para> + <para> + Fully integrated support for LiPo rechargeable batteries. + </para> </listitem> <listitem> - <para> - Uses LiPo to fire e-matches, support for optional separate pyro - battery if needed. - </para> + <para> + Uses LiPo to fire e-matches, support for optional separate pyro + battery if needed. + </para> </listitem> <listitem> - <para> - 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube. - </para> + <para> + 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube. + </para> </listitem> </itemizedlist> </chapter> @@ -223,9 +222,45 @@ </chapter> <chapter> <title>Operation</title> - <para> - Placeholder. - </para> + <section> + <title>Radio Link </title> + <para> + The chip our boards are based on incorporates 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 have to decide how to manage the + link... + </para> + <para> + By design, TeleMetrum firmware listens for an RF connection when + it's in "idle mode" (turned on while the rocket is horizontal), which + allows us to use the RF link to configure the rocket, do things like + ejection tests, and extract data after a flight without having to + crack open the airframe. However, when the board is in "flight + mode" (turned on when the rocket is vertical) the TeleMetrum 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 and out over + the RF link in case the rocket crashes and we aren't able to extract + data later... + </para> + <para> + We don't use a 'normal packet radio' mode because they're just too + inefficient. GFSK is just FSK with the baseband pulses passed through a + Gaussian filter before they go into the modulator to limit the + transmitted bandwidth. When combined with the hardware forward error + correction support in the cc1111 chip, this allows us to have a very + robust 38.4 kilobit data link with only 10 milliwatts of transmit power, + a whip antenna in the rocket, and a hand-held Yagi on the ground. We've + had a test flight above 12k AGL with good reception, and my calculations + say we should be good to 40k AGL or more with just a 5-element yagi on + the ground. I expect to push 30k with a 54mm minimum airframe I'm + working on now, so we'll hopefully have further practical confirmation + of our link margin in a few months. + </para> + <para> + Placeholder. + </para> + </section> </chapter> <chapter> <title>Using Altus Metrum Products</title> @@ -312,11 +347,11 @@ <para> The best hand-held commercial directional antennas we've found for radio direction finding rockets are from - <ulink url="http://www.arrowantennas.com/" > - Arrow Antennas. - </ulink> -The 440-3 and 440-5 are both good choices for finding a -TeleMetrum-equipped rocket when used with a suitable 70cm HT. + <ulink url="http://www.arrowantennas.com/" > + Arrow Antennas. + </ulink> + The 440-3 and 440-5 are both good choices for finding a + TeleMetrum-equipped rocket when used with a suitable 70cm HT. </para> </section> <section> |