iNav 7.1.2, struggling to set servos via MSP commands

[LeBirlante]

I'm developing a MSP implementation in order to be used on a companion computer talking to an H7-43 Wing fc with iNav 7.1.2 flashed.
In general, servos work pretty well as expected, I am able to change their midpoints (i.e., "move" them) both from iNav configurator and from CLI (via the "servo" command).

However, I'm having a hard time trying to change the servos via MSP commands. I can read all 16 servos' values correctly via a 0x78 (MSP_SERVO_CONF). However, I cannot get the FC to acknowledge neither a 0xD4 (MSP_SERVO_SET_CONF) nor a 0x2201 (MSP_INAV_SET_SERVO_CONF). In both cases I receive absolutely nothing (not even an error message) and of course servos will remain unchanged.

From /src/main/fc/fc,msp [line 2224] I've been able to find out the expected payload structure which iNav is expecting for those two MSP comands (dataSize = 15 for 0xd4, and 8 for 0x2201), being the first uint8 the number of servo you're changing the values for.

But the thing is, I cannot get something as simple and straightforward as the CLI command "servo 5 1500 2500 1600 100" to work via MSP with something like (byte message edited for clarity):

24,58,3c // msp header and direction
0 // flag
d4,0 // command code
f,0 // payload size = 15 , will be -> u8 u16 u16 u16 u8 u8 u8 u8 u32
5, f4, 1, ab, 9, 40, 6, 64, 0, 0, ff, 0, 0, 0, 0 // payload ---> 5d 500d 2475d 1600d 100d 0 0 255d 0 0 0 0
df // msp crc byte

What's somewhat confusing to me is that the FC won't even return a MSP error message, something with direction byte set to "!" for example. It will simply silently fail. Is there something I'm missing here?

thanks for your time,

[mmosca]

I am not sure you are doing the correct thing. Moving the servos, via servo command is only done during setup. It is not a way to control the craft.

Either way, you are likely sending the wrong payload, or miscaulating the crc of the msp message.

[LeBirlante]

Either way, you are likely sending the wrong payload, or miscaulating the crc of the msp message.

I tend to believe I must be doing something wrong with the payload structure (your first option), reason being that I can send other msp messages, and receive their respective answers from the FC, without any problem.... hence the crc thing has to be working ok if I can generate other msp messages.