From: Keith Packard Date: Thu, 25 Aug 2011 06:06:44 +0000 (-0700) Subject: Merge remote-tracking branch 'origin/master' X-Git-Tag: 1.0~9^2~1 X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=e268798dc260311f5f0167909481b41c9d27fc1c Merge remote-tracking branch 'origin/master' --- e268798dc260311f5f0167909481b41c9d27fc1c diff --cc doc/altusmetrum.xsl index c778b1e1,c8ffedac..aeb43acb --- a/doc/altusmetrum.xsl +++ b/doc/altusmetrum.xsl @@@ -583,154 -583,7 +583,80 @@@ NAR #88757, TRA #1220 simultaneously. +
+ Maximum Flight Log + + TeleMetrum version 1.1 has 2MB of on-board flash storage, + enough to hold over 40 minutes of data at full data rate + (100 samples/second). TeleMetrum 1.0 has 1MB of on-board + storage. As data are stored at a reduced rate during + descent, there's plenty of space to store many flights worth + of data. + + + The on-board flash is partitioned into separate flight logs, + each of a fixed maximum size. Increase the maximum size of + each log and you reduce the number of flights that can be + stored. Decrease the size and TeleMetrum can store more + flights. + + + All of the configuration data is also stored in the flash + memory, which consumes 64kB on TeleMetrum v1.1 and 256B on + TeleMetrum v1.0. This configuration space is not available + for storing flight log data. + + + To compute the amount of space needed for a single flight, + you can multiply the expected ascent time (in seconds) by + 800, multiply the expected descent time (in seconds) by 80 + and add the two together. That will slightly under-estimate + the storage (in bytes) needed for the flight. For instance, + a flight spending 20 seconds in ascent and 150 seconds in + descent will take about (20 * 800) + (150 * 80) = 28000 + bytes of storage. You could store dozens of these flights in + the on-board flash. + + + The default size, 192kB, allows for 10 flights of storage on + TeleMetrum v1.1 and 5 flights on TeleMetrum v1.0. This + ensures that you won't need to erase the memory before + flying each time while still allowing more than sufficient + storage for each flight. + +
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+ 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 that has two + TeleMetrum computers, 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. + +
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+ Pad Orientation + + TeleMetrum measures 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, TeleMetrum must be + explicitly configured for either Antenna Up or Antenna + Down. The default, Antenna Up, expects the end of the + TeleMetrum board connected to the 70cm antenna to be nearest + the nose of the rocket, with the end containing the screw + terminals nearest the tail. + +
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- Calibration - - There are only two calibrations required for a TeleMetrum board, and - only one for TeleDongle and TeleMini. - -
- Radio Frequency - - The radio frequency is synthesized from a clock based on the 48 MHz - crystal on the board. The actual frequency of this oscillator must be - measured to generate a calibration constant. While our GFSK modulation - bandwidth is wide enough to allow boards to communicate even when - their oscillators are not on exactly the same frequency, performance - is best when they are closely matched. - Radio frequency calibration requires a calibrated frequency counter. - Fortunately, once set, the variation in frequency due to aging and - temperature changes is small enough that re-calibration by customers - should generally not be required. - - - When the radio calibration value is changed, the radio - frequency value is reset to the same value, so you'll need - to recompute and reset the radio frequency value using the - new radio calibration value. - -
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- TeleMetrum Accelerometer - - The TeleMetrum accelerometer we use has its own 5 volt power supply and - the output must be passed through a resistive voltage divider to match - the input of our 3.3 volt ADC. This means that unlike the barometric - sensor, the output of the acceleration sensor is not ratio-metric to - the ADC converter, and calibration is required. We also support the - use of any of several accelerometers from a Freescale family that - includes at least +/- 40g, 50g, 100g, and 200g parts. Using gravity, - a simple 2-point calibration yields acceptable results capturing both - the different sensitivities and ranges of the different accelerometer - parts and any variation in power supply voltages or resistor values - in the divider network. - - - To calibrate the acceleration sensor, use the 'c a 0' command. You - will be prompted to orient the board vertically with the UHF antenna - up and press a key, then to orient the board vertically with the - UHF antenna down and press a key. - As with all 'c' sub-commands, follow this with a 'c w' to write the - change to the parameter block in the on-board DataFlash chip. - - - The +1g and -1g calibration points are included in each telemetry - frame and are part of the header extracted by ao-dumplog after flight. - Note that we always store and return raw ADC samples for each - sensor... nothing is permanently "lost" or "damaged" if the - calibration is poor. - - - In the unlikely event an accel cal that goes badly, it is possible - that TeleMetrum may always come up in 'pad mode' and as such not be - listening to either the USB or radio link. If that happens, - there is a special hook in the firmware to force the board back - in to 'idle mode' so you can re-do the cal. To use this hook, you - just need to ground the SPI clock pin at power-on. This pin is - available as pin 2 on the 8-pin companion connector, and pin 1 is - ground. So either carefully install a fine-gauge wire jumper - between the two pins closest to the index hole end of the 8-pin - connector, or plug in the programming cable to the 8-pin connector - and use a small screwdriver or similar to short the two pins closest - to the index post on the 4-pin end of the programming cable, and - power up the board. It should come up in 'idle mode' (two beeps). - -
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