- 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[]
-
projects / fw / altos / blobdiff