+== System Operation
+
+ === Firmware Modes
+
+ The AltOS firmware build for the altimeters has two
+ fundamental modes, “idle” and “flight”. Which of these modes
+ the firmware operates in is determined at start up time. For
+ TeleMetrum, TeleMega and EasyMega, which have accelerometers, the mode is
+ controlled by the orientation of the
+ rocket (well, actually the board, of course...) at the time
+ power is switched on. If the rocket is “nose up”, then
+ the flight computer assumes it's on a rail or rod being prepared for
+ launch, so the firmware chooses flight mode. However, if the
+ rocket is more or less horizontal, the firmware instead enters
+ idle mode. Since TeleMini v2.0 and EasyMini don't have an
+ accelerometer we can use to determine orientation, “idle” mode
+ is selected if the board is connected via USB to a computer,
+ otherwise the board enters “flight” mode. TeleMini v1.0
+ selects “idle” mode if it receives a command packet within the
+ first five seconds of operation.
+
+ At power on, the altimeter will beep out the battery voltage
+ to the nearest tenth of a volt. Each digit is represented by
+ a sequence of short “dit” beeps, with a pause between
+ digits. A zero digit is represented with one long “dah”
+ beep. Then there will be a short pause while the altimeter
+ 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="1,1,1,1"]
+ |====
+ |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
+ by an “di-dah-dah-dit” (“P” for pad) on the beeper or lights,
+ followed by beeps or flashes indicating the state of the
+ pyrotechnic igniter continuity. One beep/flash indicates
+ apogee continuity, two beeps/flashes indicate main continuity,
+ three beeps/flashes indicate both apogee and main continuity,
+ and one longer “brap” sound which is made by rapidly
+ alternating between two tones indicates no continuity. For a
+ dual deploy flight, make sure you're getting three beeps or
+ flashes before launching! For apogee-only or motor eject
+ flights, do what makes sense.
+
+ If idle mode is entered, you will hear an audible “di-dit” or
+ see two short flashes (“I” for idle), and the flight state
+ machine is disengaged, thus no ejection charges will fire.
+ The altimeters also listen for the radio link when in idle
+ mode for requests sent via TeleDongle. Commands can be issued
+ in idle mode over either USB or the radio link
+ equivalently. TeleMini v1.0 only has the radio link. Idle
+ mode is useful for configuring the altimeter, for extracting
+ data from the on-board storage chip after flight, and for
+ ground testing pyro charges.
+
+ In “Idle” and “Pad” modes, once the mode indication
+ beeps/flashes and continuity indication has been sent, if
+ there is no space available to log the flight in on-board
+ memory, the flight computer will emit a warbling tone (much
+ slower than the “no continuity tone”)
+
+ Here's a summary of all of the “pad” and “idle” mode indications.
+
+ .Pad/Idle Indications
+ [options="header",cols="1,1,1"]
+ |====
+ |Name |Beeps |Description
+
+ |Neither
+ |brap
+ |No continuity detected on either apogee or main igniters.
+
+ |Apogee
+ |dit
+ |Continuity detected only on apogee igniter.
+
+ |Main
+ |dit dit
+ |Continuity detected only on main igniter.
+
+
+ |Both
+ |dit dit dit
+ |Continuity detected on both igniters.
+
+
+ |Storage Full
+ |warble
+ |On-board data logging storage is full. This will
+ not prevent the flight computer from safely
+ controlling the flight or transmitting telemetry
+ signals, but no record of the flight will be
+ stored in on-board flash.
+ |====
+
+ Once landed, the flight computer will signal that by emitting
+ the “Landed” sound described above, after which it will beep
+ out the apogee height (in meters). Each digit is represented
+ by a sequence of short “dit” beeps, with a pause between
+ digits. A zero digit is represented with one long “dah”
+ beep. The flight computer will continue to report landed mode
+ and beep out the maximum height until turned off.
+
+ One “neat trick” of particular value when TeleMetrum, TeleMega
+ or EasyMega are used with
+ very large air-frames, is that you can power the board up while the
+ rocket is horizontal, such that it comes up in idle mode. Then you can
+ raise the air-frame to launch position, and issue a 'reset' command
+ via TeleDongle over the radio link to cause the altimeter to reboot and
+ come up in flight mode. This is much safer than standing on the top
+ step of a rickety step-ladder or hanging off the side of a launch
+ tower with a screw-driver trying to turn on your avionics before
+ installing igniters!
+
+ TeleMini v1.0 is configured solely via the radio link. Of course, that
+ means you need to know the TeleMini radio configuration values
+ or you won't be able to communicate with it. For situations
+ when you don't have the radio configuration values, TeleMini v1.0
+ offers an 'emergency recovery' mode. In this mode, TeleMini is
+ configured as follows:
+
+
+ * Sets the radio frequency to 434.550MHz
+ * Sets the radio calibration back to the factory value.
+ * Sets the callsign to N0CALL
+ * Does not go to 'pad' mode after five seconds.
+
+ To get into 'emergency recovery' mode, first find the row of
+ four small holes opposite the switch wiring. Using a short
+ piece of small gauge wire, connect the outer two holes
+ together, then power TeleMini up. Once the red LED is lit,
+ disconnect the wire and the board should signal that it's in
+ 'idle' mode after the initial five second startup period.
+
+ === GPS
+
+ TeleMetrum and TeleMega include a complete GPS receiver. A
+ complete explanation of how GPS works is beyond the scope of
+ this manual, but the bottom line is that the GPS receiver
+ needs to lock onto at least four satellites to obtain a solid
+ 3 dimensional position fix and know what time it is.
+
+ The flight computers provide backup power to the GPS chip any time a
+ battery is connected. This allows the receiver to “warm start” on
+ the launch rail much faster than if every power-on were a GPS
+ “cold start”. In typical operations, powering up
+ on the flight line in idle mode while performing final air-frame
+ preparation will be sufficient to allow the GPS receiver to cold
+ start and acquire lock. Then the board can be powered down during
+ RSO review and installation on a launch rod or rail. When the board
+ is turned back on, the GPS system should lock very quickly, typically
+ long before igniter installation and return to the flight line are
+ complete.
+
+ === Controlling An Altimeter Over The Radio Link
+
+ One of the unique features of the Altus Metrum system is the
+ ability to create a two way command link between TeleDongle
+ and an altimeter using the digital radio transceivers
+ built into each device. This allows you to interact with the
+ altimeter from afar, as if it were directly connected to the
+ computer.
+
+ Any operation which can be performed with a flight computer can
+ either be done with the device directly connected to the
+ computer via the USB cable, or through the radio
+ link. TeleMini v1.0 doesn't provide a USB connector and so it is
+ always communicated with over radio. Select the appropriate
+ TeleDongle device when the list of devices is presented and
+ AltosUI will interact with an altimeter over the radio link.
+
+ One oddity in the current interface is how AltosUI selects the
+ frequency for radio communications. Instead of providing
+ an interface to specifically configure the frequency, it uses
+ whatever frequency was most recently selected for the target
+ TeleDongle device in Monitor Flight mode. If you haven't ever
+ used that mode with the TeleDongle in question, select the
+ Monitor Flight button from the top level UI, and pick the
+ appropriate TeleDongle device. Once the flight monitoring
+ window is open, select the desired frequency and then close it
+ down again. All radio communications will now use that frequency.
+
+ * Save Flight Data—Recover flight data from the
+ rocket without opening it up.
+
+ * Configure altimeter apogee delays, main deploy
+ heights and additional pyro event conditions to
+ respond to changing launch conditions. You can also
+ 'reboot' the altimeter. Use this to remotely enable
+ the flight computer by turning TeleMetrum or
+ TeleMega on in “idle” mode, then once the air-frame
+ is oriented for launch, you can reboot the
+ altimeter and have it restart in pad mode without
+ having to climb the scary ladder.
+
+ * Fire Igniters—Test your deployment charges without snaking
+ wires out through holes in the air-frame. Simply assemble the
+ rocket as if for flight with the apogee and main charges
+ loaded, then remotely command the altimeter to fire the
+ igniters.
+
+ Operation over the radio link for configuring an
+ altimeter, ground testing igniters, and so forth uses
+ the same RF frequencies as flight telemetry. To
+ configure the desired TeleDongle frequency, select the
+ monitor flight tab, then use the frequency selector
+ and close the window before performing other desired
+ radio operations.
+
+ The flight computers only enable radio commanding in
+ 'idle' mode. TeleMetrum and TeleMega use the
+ accelerometer to detect which orientation they start
+ up in, so make sure you have the flight computer lying
+ horizontally when you turn it on. Otherwise, it will
+ start in 'pad' mode ready for flight, and will not be
+ listening for command packets from TeleDongle.
+
+ TeleMini listens for a command packet for five seconds
+ after first being turned on, if it doesn't hear
+ anything, it enters 'pad' mode, ready for flight and
+ will no longer listen for command packets. The easiest
+ way to connect to TeleMini is to initiate the command
+ and select the TeleDongle device. At this point, the
+ TeleDongle will be attempting to communicate with the
+ TeleMini. Now turn TeleMini on, and it should
+ immediately start communicating with the TeleDongle
+ and the desired operation can be performed.
+
+ You can monitor the operation of the radio link by watching the
+ lights on the devices. The red LED will flash each time a packet
+ is transmitted, while the green LED will light up on TeleDongle when
+ it is waiting to receive a packet from the altimeter.
+
+ === Ground Testing
+
+ An important aspect of preparing a rocket using electronic deployment
+ for flight is ground testing the recovery system. Thanks
+ to the bi-directional radio link central to the Altus Metrum system,
+ this can be accomplished in a TeleMega, TeleMetrum or TeleMini equipped rocket
+ with less work than you may be accustomed to with other systems. It
+ can even be fun!
+
+ Just prep the rocket for flight, then power up the altimeter
+ in “idle” mode (placing air-frame horizontal for TeleMetrum or TeleMega, or
+ selecting the Configure Altimeter tab for TeleMini). This will cause
+ the firmware to go into “idle” mode, in which the normal flight
+ state machine is disabled and charges will not fire without
+ manual command. You can now command the altimeter to fire the apogee
+ or main charges from a safe distance using your computer and
+ TeleDongle and the Fire Igniter tab to complete ejection testing.
+
+ === 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
+ 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="1,1,1"]
+ |====
+ |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.
+
+ === 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:
+
+ Acceleration:: Select a value, and then choose
+ whether acceleration should be above or below
+ that value. Acceleration is positive upwards,
+ so accelerating towards the ground would
+ produce negative numbers. Acceleration during
+ descent is noisy and inaccurate, so be careful
+ when using it during these phases of the
+ flight.
+
+ Vertical speed:: Select a value, and then
+ choose whether vertical speed should be above
+ or below that value. Speed is positive
+ upwards, so moving towards the ground would
+ produce negative numbers. Speed during descent
+ is a bit noisy and so be careful when using it
+ during these phases of the flight.
+
+ Height:: Select a value, and then choose
+ whether the height above the launch pad should
+ be above or below that value.
+
+ Orientation:: TeleMega and EasyMega contain a
+ 3-axis gyroscope and accelerometer which is
+ used to measure the current angle. Note that
+ this angle is not the change in angle from the
+ launch pad, but rather absolute relative to
+ gravity; the 3-axis accelerometer is used to
+ compute the angle of the rocket on the launch
+ pad and initialize the system.
+
+ [NOTE]
+ ====
+ Because this value is computed by integrating
+ rate gyros, it gets progressively less
+ accurate as the flight goes on. It should have
+ an accumulated error of less than 0.2°/second
+ (after 10 seconds of flight, the error should
+ be less than 2°).
+
+ The usual use of the orientation configuration
+ is to ensure that the rocket is traveling
+ mostly upwards when deciding whether to ignite
+ air starts or additional stages. For that,
+ choose a reasonable maximum angle (like 20°)
+ and set the motor igniter to require an angle
+ of less than that value.
+ ====
+
+ Flight Time:: Time since boost was
+ detected. Select a value and choose whether to
+ activate the pyro channel before or after that
+ amount of time.
+
+ Ascending:: A simple test saying whether the
+ rocket is going up or not. This is exactly
+ equivalent to testing whether the speed is
+ > 0.
+
+ Descending:: A simple test saying whether the
+ rocket is going down or not. This is exactly
+ equivalent to testing whether the speed is
+ < 0.
+
+ After Motor:: The flight software counts each
+ time the rocket starts accelerating and then
+ decelerating (presumably due to a motor or
+ motors burning). Use this value for
+ multi-staged or multi-airstart launches.
+
+ Delay:: This value doesn't perform any checks,
+ instead it inserts a delay between the time
+ when the other parameters become true and when
+ the pyro channel is activated.
+
+ Flight State:: The flight software tracks the flight
+ through a sequence of states:
+
+ * Boost. The motor has lit and the rocket is
+ accelerating upwards.
+
+ * Fast. The motor has burned out and the
+ rocket is decelerating, but it is going
+ faster than 200m/s.
+
+ * Coast. The rocket is still moving upwards
+ and decelerating, but the speed is less
+ than 200m/s.
+
+ * Drogue. The rocket has reached apogee and
+ is heading back down, but is above the
+ configured Main altitude.
+
+ * Main. The rocket is still descending, and
+ is below the Main altitude
+
+ * Landed. The rocket is no longer moving.
+
+ You can select a state to limit when the pyro
+ channel may activate; note that the check is
+ based on when the rocket transitions *into*
+ the state, and so checking for “greater than
+ Boost” means that the rocket is currently in
+ boost or some later state.
+
+ When a motor burns out, the rocket enters
+ either Fast or Coast state (depending on how
+ fast it is moving). If the computer detects
+ upwards acceleration again, it will move back
+ to Boost state.
projects / fw / altos / commitdiff