Maximum Number of Servos

Zak5254 · September 18, 2020, 6:59pm

Hello all,

I tried searching the web for this but I wasn’t able to find any definitive answer to my simple question.

What would be the maximum number of servos that could be driven via CAN? I’m looking to drive up to 20 servos. Not sure if that is possible though. I know the CAN line could handle it but I’m not sure if the firmware can.

Thanks in advanced for any help!

TunaLobster · September 18, 2020, 9:14pm

I believe there is a maximum of 16 servo channels currently. The bit of code for that is here. I don’t know if that could be increased and assigned to outputs easily.

github.com

ArduPilot/ardupilot/blob/master/libraries/SRV_Channel/SRV_Channel.h#L24


#pragma once


#include <AP_Common/AP_Common.h>
#include <AP_Param/AP_Param.h>
#include <AP_Common/Bitmask.h>
#include <AP_Volz_Protocol/AP_Volz_Protocol.h>
#include <AP_RobotisServo/AP_RobotisServo.h>
#include <AP_SBusOut/AP_SBusOut.h>
#include <AP_BLHeli/AP_BLHeli.h>


#define NUM_SERVO_CHANNELS 16


class SRV_Channels;


/*
  class SRV_Channel. The class SRV_Channels contains an array of
  SRV_Channel objects. This is done to fit within the AP_Param limit
  of 64 parameters per object.
*/
class SRV_Channel {
public:

peterbarker · September 19, 2020, 3:35am

There are a whole bunch of masks floating around which are 16-bits long.
All of those would need to be hunted down and changed to 32-bits.

Zak5254 · September 23, 2020, 8:23pm

Thanks guys,

I might have to go down the route of hunting those all down though. I’m sure there are other way to make this work but for the purpose of having full individual servo logging I think this might be my only choice. I’ll be sure to try to keep this updated as I make progress.