Use PWM inputs to control motors

lroberts · Feb 24, 2017

Hi everyone!
I'd like to use PWM outputs from my Edison kit for Arduino to provide PWM inputs to my Solo drone. I want these PWM inputs to control the motors of Solo. I have the accessory breakout board found here 3DR Solo Accessory Breakout Board

Can I access the PWM ports on Solo to do this? If so, which ports? Is it the IO-PWM6, 7, and 8? Or should I use the ch6, 7, and 8? I've been searching everywhere for an answer to this, but I'm not finding any definitive information for doing this on Solo.

Thanks!

Pedals2Paddles · Feb 24, 2017

The pixhawk does not take PWM INPUTS for anything. PWM, Serial, i2c, etc are the inputs.

lroberts · Feb 24, 2017

Thanks for your reply! Can you clarify, then, how I can use PWM as an input? I'm not entirely sure what you mean; if the pixhawk doesn't take PWM input, is PWM still an input for something else?

I am not very familiar with how the Solo works with these inputs, so thanks for your patience.

Pedals2Paddles · Feb 24, 2017

The pixhawk does not use PWM inputs for anything at all. Inputs are all via PPM, serial, i2c, etc. You cannot directly connect PWM inputs to the Pixhawk. The PPM input is there. You could get a PWM to PPM converter, and feed the inputs using the PPM input. That's how you would connect an older PWM only RC Receiver to any Pixhawk that doesn't have PWM inputs on a custom built drone too. Now, how you make the Pixhawk listen to that PPM input rather than the control inputs from the companion computer, I don't actually know. It will likely require some hardware or firmware changes.

lroberts · Feb 26, 2017

Ok, thanks for the info. That is disappointing...out of curiosity, what is the IO-PWM6, 7, and 8 ports on the breakout board used for? Also, what can we use the ch6, 7, and 8 used for?

Thanks!

Pedals2Paddles · Feb 26, 2017

Those are for outputs from the pixhawk. 7 and 8 on the pixhawk are aux outputs. But their usefulness on the solo is limited. Channel 7 output is activated by long pressing the pause button. But that also activates rewind. Channel 8 has no connection to the accessory bay.

lroberts · Feb 27, 2017

Do you know of any other way I can control Solo's motors? I need to use Solo to track objects, but because I need a non-gps dependent environment and Solo does not currently support the guided_nogps command, I cannot really do this with MAVLink. Is there some other way I can control Solo's movements? Thanks for your input.

human · Feb 27, 2017

The motors are controlled by the ESC boards, which take input from the Pixhawk flight controller. The source code for the flight controller is here:

GitHub - 3drobotics/ardupilot-solo

Keep in mind that many of Solo's software components are closed source, including much of the comm stack. There also isn't much documentation available.

Having prior experience with real-time software development, . microcontrollers, C++, Linux, and Python is definitely helpful!

lroberts · Feb 28, 2017

Thanks for those tips, @human . Also @Pedals2Paddles what is the port for PPM input? I've looked for documentation on these sorts of questions, but I'm not finding a lot of information. I've found these pages to be somewhat useful.
Extend 3DR Solo Accessory Bay - Hackster.io
https://dev.3dr.com/hardware-accessorybay.html
Do you know of another link where I could find information on these ports?

Pedals2Paddles · Mar 1, 2017

The accessory port will not provide any means to give flight control INPUTS to the pixhawk.

I did some Intel gathering on this matter. I've been curious myself. You can connect a conventional PPM RC receiver or a PPM converter connected to your PWM outputs, to the PPM Input terminal on the Solo's main board under the battery tray. That will allow you to feed conventional flight control inputs directly to the pixhawk. Just like you would on a custom built drone with a pixhawk. However, you need to kill the Spektrum process on the companion computer so it stops feeding the Solo's controller input at the same time. Someone familiar with the companion computer code can make that happen.

The smart shots, rewind, RTH, and RTM all will still work as usual since those go over serial to the pixhawk in guided mode.