This golang program exercises MSP_SET_RAW_RC. This is intended to be a learning / experimental / educational tool rather than an end user application.
Every few months, someone will come along on INAV Github / RC Groups / Telegram / Discord / some other random support channel and state that RX_MSP / set receiver_type = MSP doesn't work.
Well it does, if you do it correctly. This example demonstrates usage.
As Go is available on pretty much any OS, you can even verify that it works, with this small application.
NOTE: The previous, verbose, timer activated version of this tool is now in the legacy branch, should you really want to play with that
- A supported FC
- INAV v6 or later, earlier versions may also work
- The FC should have been configured to a state in which it can be armed:
- The sensors are calibrated
- Required sensors are powered (e.g. GPS requiring battery)
- If necessary
nav_extra_arming_safetymay be set toALLOW_BYPASS - The arming channel is defined, with a range (min-max) less than 1000
Modern firmware (e.g INAV 1.8 and later)
set receiver_type = MSP
For older versions of this example, with INAV prior to INAV 1.8, you can try:
# for ancient firmware
feature RX_MSP
However, don't be surprised if ancient versions fail to work with msp_set_rx.
- Clone this repository
- Build the test application
# gmake on 'BSD
make
This should result in a msp_set_rx application.
For Windows (cross compile on non-Windows:)
GOOS=windows go build -ldflags "-w -s" -o msp_set_rx.exe msp.go msp_set_rx.go btaddr_other.go inav_misc.go event_loop.go
Natively, drop the GOOS=windows bit. With msys2, you can (probably) use the Makefile.
$ msp_set_rx --help
Usage of msp_set_rx [options]
-auto-arm
Auto-arm FC when ready
-b int
Baud rate (default 115200)
-d string
Serial Device
-every int
Refresh time (ms) (default 100)
-throttle int
Low throttle (µs) (default -1)
-verbose
log Rx/Tx stanzas
When initialised, the application will accept keypresses:
A,a: Toggle arming state- If the FC is in a "ready to arm" condition, it will be armed
- If the FC is armed, it will be disarmed
Q,q,Ctrl-C: Clean exit. If the FC is armed, it will be disarmed first.F: Unclean exit, potentially causing fail-safe. Be prepared to handle the consequences.v,V: Toggle verbose
If a -throttle value has been specified, then, when armed it will run the motors at that value and the throttle will not be randomly perturbed. Two additional keypresses are recognised:
+,-raise / lower throttle by 25µs
If the application is exited uncleanly, then on restarting msp_set_rx, the FC should recover from fail-safe (note roll and pitch are perturbed to force F/S recovery).
$ ./msp_set_rx -d /dev/ttyUSB0 [-b baud]
# and hence, probably, for example
C:\> msp_set_rx.exe -d COM42 -b 115200
# Linux, autodetect
$ ./msp_set_rx
Note: On Linux, /dev/ttyUSB0 and /dev/ttyACM0 are automatically detected.
While this tool attempts to arm at a safe throttle value, removing props or using a current limiter is recommended. Using the INAV_SITL may be a better option. A suitable configuration for such experiments is described in the fl2sitl wiki
Please also note that if you do not define a "low throttle" (-throttle) value, then when armed, the motors will run at randomly changing throttle between 1100us and 1300us. Please ensure you and your hardware are content with this.
By default, the RC values are refreshed every 100ms (10Hz), twice the required minimum refresh rate. With -every 200, then RC values are updated every 200ms (5Hz). This should not failsafe, however any value greater than 200 will failsafe.
-every 200: works-every 201: never comes out of failsafe.
./msp_set_rx
[msp_set_rx] 19:20:08.885594 Using device /dev/ttyACM0
INAV v7.0.0 WINGFC (497c01eb) API 2.5
nav_extra_arming_safety: 2 (bypass true)
map: AETR
name: "BENCHYMCTESTY"
box: ARM;PREARM;MULTI FUNCTION;ANGLE;HORIZON;TURN ASSIST;HEADING HOLD;CAMSTAB;NAV POSHOLD;LOITER CHANGE;NAV RTH;NAV WP;NAV CRUISE;NAV COURSE HOLD;HOME RESET;GCS NAV;WP PLANNER;MISSION CHANGE;SOARING;NAV ALTHOLD;MANUAL;NAV LAUNCH;SERVO AUTOTRIM;AUTO TUNE;AUTO LEVEL TRIM;BEEPER;BEEPER MUTE;OSD OFF;BLACKBOX;KILLSWITCH;FAILSAFE;CAMERA CONTROL 1;CAMERA CONTROL 2;CAMERA CONTROL 3;OSD ALT 1;OSD ALT 2;OSD ALT 3;MIXER PROFILE 2;MIXER TRANSITION;
chan: 5, start: 1300, end: 1700 NAV POSHOLD
chan: 5, start: 1700, end: 2100 NAV RTH
chan: 6, start: 1300, end: 2100 NAV WP
chan: 7, start: 1700, end: 2100 NAV ALTHOLD
chan: 7, start: 1700, end: 2100 NAV COURSE HOLD
chan: 8, start: 1375, end: 1600 NAV LAUNCH
chan: 10, start: 1500, end: 2100 ARM
chan: 11, start: 1450, end: 2100 MANUAL
chan: 12, start: 1600, end: 2100 BEEPER
Arming set for channel 10 / 1800us
Keypresses: 'A'/'a': toggle arming, 'Q'/'q': quit, 'F': quit to failsafe
[msp_set_rx] 19:20:09.101738 Start TX loop
[msp_set_rx] 19:20:09.228487 Box: FAILSAFE (40000000) Arm: RCLink (0x40000)
[msp_set_rx] 19:20:09.932720 Box: (0) Arm: Ready to arm (0x0)
Depending on how early in the boot process you start msp_set_rx, you may also see some calibration messages.
Having reached the "Ready to arm" state, if you press A, the FC will be armed:
[msp_set_rx] 19:31:55.324435 Box: ARM (1) Arm: Armed (0xc)
And if A is pressed again, the FC is disarmed:
[msp_set_rx] 19:33:36.633957 Box: (0) Arm: Ready to arm (0x8)
Pressing Q or Ctrl-C will exit the application, if the FC is armed, it will be disarmed first.
$ ./msp_set_rx
...
[msp_set_rx] 08:55:50.226087 Start TX loop
[msp_set_rx] 08:55:50.327397 Box: FAILSAFE (40000000) Arm: Ever armed RCLink (0x40028)
[msp_set_rx] 08:55:51.027408 Box: (0) Arm: Ever armed RCLink (0x40028)
[msp_set_rx] 08:55:51.127391 Box: (0) Arm: Ready to arm (0x28)
[msp_set_rx] 08:55:53.107915 Arming commanded # <---------- Press A key
[msp_set_rx] 08:55:53.228029 Box: ARM (1) Arm: Armed (0x2c)
[msp_set_rx] 08:55:55.511591 Quit commanded # <---------- Press Q key
[msp_set_rx] 08:55:55.828115 Box: (0) Arm: Ready to arm (0x28)
Use F key press to exit without disarming, causing fail-safe:
$ ./msp_set_rx
...
msp_set_rx] 08:57:56.794411 Box: (0) Arm: Ready to arm (0x28)
[msp_set_rx] 08:57:57.998486 Arming commanded
[msp_set_rx] 08:57:58.195017 Box: ARM (1) Arm: Armed (0x2c)
[msp_set_rx] 08:58:01.214484 Exit to F/S commanded # <---------- Press F key
If we restart after failsafe:
$ ./msp_set_rx
...
[msp_set_rx] 08:58:48.488756 Start TX loop
[msp_set_rx] 08:58:48.590155 Box: ARM,ANGLE,FAILSAFE (40000009) Arm: Armed (0x2c)
[msp_set_rx] 08:58:49.489689 Box: ARM (1) Arm: Armed (0x2c)
Note the FC "Box" state shows ARM,ANGLE,FAILSAFE, and that we are still armed. It then quickly recovers (0.5s, i.e. meeting the required RX update rate) to a normal armed state, from which we can disarm / quit cleanly.
You can also use the INAV SITL to test. This has the advantage of not requiring hardware. The same arming prerequisites apply.
Here we specify the armed throttle and auto-arm:
$ ./msp_set_rx -d tcp://localhost:5761 -throttle 1200 -auto-arm
[msp_set_rx] 21:09:56.436998 Using device localhost
INAV v7.0.0 SITL (3a2412e5) API 2.5
nav_extra_arming_safety: 2 (bypass true)
map: AETR
name: "BENCHYMCTESTY"
box: ARM;PREARM;MULTI FUNCTION;ANGLE;HORIZON;TURN ASSIST;HEADING HOLD;CAMSTAB;NAV POSHOLD;LOITER CHANGE;NAV RTH;NAV WP;NAV CRUISE;NAV COURSE HOLD;HOME RESET;GCS NAV;WP PLANNER;MISSION CHANGE;SOARING;NAV ALTHOLD;MANUAL;NAV LAUNCH;SERVO AUTOTRIM;AUTO TUNE;AUTO LEVEL TRIM;BEEPER;BEEPER MUTE;OSD OFF;BLACKBOX;KILLSWITCH;FAILSAFE;CAMERA CONTROL 1;CAMERA CONTROL 2;CAMERA CONTROL 3;OSD ALT 1;OSD ALT 2;OSD ALT 3;
chan: 5, start: 1300, end: 1700 NAV POSHOLD
chan: 5, start: 1700, end: 2100 NAV RTH
chan: 6, start: 1300, end: 2100 NAV WP
chan: 7, start: 1700, end: 2100 NAV ALTHOLD
chan: 7, start: 1700, end: 2100 NAV COURSE HOLD
chan: 8, start: 1375, end: 1600 NAV LAUNCH
chan: 10, start: 1500, end: 2100 ARM
chan: 11, start: 1450, end: 2100 MANUAL
chan: 12, start: 1600, end: 2100 BEEPER
Arming set for channel 10 / 1800us
Keypresses: 'A'/'a': toggle arming, 'Q'/'q': quit, 'F': quit to failsafe
'+'/'-' raise / lower throttle by 25µs
[msp_set_rx] 09:01:06.155880 Start TX loop
[msp_set_rx] 09:01:06.256949 Box: FAILSAFE (40000000) Arm: Ever armed RCLink (0x40028)
[msp_set_rx] 09:01:06.956972 Box: (0) Arm: Ever armed RCLink (0x40028)
[msp_set_rx] 09:01:07.056953 Box: (0) Arm: Ready to arm (0x28)
[msp_set_rx] 09:01:07.256960 Box: ARM (1) Arm: Armed (0x2c)
[msp_set_rx] 09:01:11.826990 Throttle commanded: 1225
[msp_set_rx] 09:01:13.493910 Throttle commanded: 1250
[msp_set_rx] 09:01:14.971894 Throttle commanded: 1275
[msp_set_rx] 09:01:21.384503 Throttle commanded: 1250
[msp_set_rx] 09:01:21.943347 Throttle commanded: 1225
[msp_set_rx] 09:01:22.515390 Throttle commanded: 1200
[msp_set_rx] 09:01:23.069359 Throttle commanded: 1175
[msp_set_rx] 09:01:29.362560 Quit commanded
[msp_set_rx] 09:01:29.756786 Box: (0) Arm: Ready to arm (0x28)
Note that the SITL captures some of the early status / calibration changes.
- The FC was armed as soon as it was ready, without user input. When armed, the user adjusted the throttle. The effects may be noted using the configurator on tcp://localhost:5760.
- The /- keys are used to manually change the throttle value.
- Configure two MSP ports, one can be used for the MSP RX, the other to inspect the RX channels in the configurator.
In one terminal (with eeprom.bin pre-configured for MSP receiver), POSIXally at least:
((fl2sitl --minimal&) && inav_SITL --path ~/sitl-eeproms/fw-eeprom.bin --sim xp)
Then (another terminal / tab):
msp_set_rx -d tcp://localhost:5761 [other otptions...]
Note that in order for the SITL to arm, a simulator is needed.In the example we use fl2sitl with -minimal to provide the simplest simulation that will unlock the SITL sensors and allow arming.
- The configurator can be connected to tcp://localhost:5760 (UART1)
- The MSP RX is connected to tcp://localhost:5761 (UART2)
There is a simple tool to interpret arming status arm_status. It accepts one or more numeric status codes and displays human readable interpretation:
./arm_status 28 84c00
Status 00000028:
00000008 => Ever Armed
00000020 => SITL
Status 00084c00:
00000400 => Overload
00000800 => Navigation unsafe
00004000 => Arm switch
00080000 => Throttle
Copy it onto $PATH if you wish.
The flightlog2kml project contains a tool fl2sitl that replays a blackbox log using the INAV SITL. Specifically, this uses MSP and MSP_SET_RAW_RC to establish vehicle characteristics, monitor the vehicle status, arm the vehicle and set RC values for AETR and switches during log replay simulation to effectively "fly" the SITL for the recorded flight.
The MSP initialisation, MSP status monitoring and MSP RC management code is in msp.go, specifically the init() and run() functions. Arming / disarming in sitlgen.go, arm_action() function.
This is more comprehensive (and complex) example.
- Ensure you provide (at least) 5Hz RX data, but don't overload the FC; MSP is a request-response protocol, don't just "spam" the FC via a high frequency timer and ignore the responses.
- Ensure you've set a correct, valid AUX range to arm. In particular and for safety, the ARM range must be less or equal to 1000 in order to allow disarming.
- Ensure you've met the required arming conditions
- Use a supported FC or the inav_SITL
- Remove the props etc.
Really, it's all about preparation, in particular the interrogation of the FC prior to sending any MSP_SET_RAW_RC data in order to get the box names and switch settings that will be necessary to arm and monitor the "box" and "arming" flags that enable your application to monitor the state of the automated FC.
Whatever approximates to none / public domain in your locale. 0BSD (Zero clause BSD) if an actual license is required by law.