RC_raw not working

I'm working in a research project with ROS flight and I'm trying to build a quadrotor and setup the hardware and firmware properly.
I'm currently having problems with the RC_raw input.
I'm using a raspberry pi for onboard computer and a Flip 32 flight controller. I also have a HK-T6A V2 RC transmitter and its receiver. This receiver do not support PPM signal, neither the controller have any receiver that support PPM, so I'm trying to use the Parallel PWM configuration, and have set the RC_TYPE parameter in rosflight to "0".
However, when I echo the rc_raw topic on the screen, all the values shown are equal to "0". The rosflight_io node is working properly on the firmware, the /imu/data topic print the orientation data correctly, and when i call the calibration service it works. I can also set and get any parameters.
I've measured the output signal from the receptor and it works as expected, changing when i change the sticks positions on the controller. This signal is a PWM pulse from 1ms to 2ms with 50 Hz.
Can anyone help me? Maybe I'm wiring the Flip 32 wrong, but i coudn't found any instructions on the ROS_flight site about this specific wiring, so I've connected the channels of the receptor as the picture in the link below, from right to left.

Flip 32 Wiring: http://cdna2.zoeysite.com/Adzpo594RQGDpLcjBynL1z/cache=expiry:31536000/resize=fit:max,width:1200/compress/http://s3.amazonaws.com/zcom-media/sites/a0iE000000GWIo4IAH/media/catalog/product/f/l/flip32layout.jpg

Thank you for your help!



  • 5 Comments sorted by Votes Date Added
  • Hi, welcome to ROSflight!

    Since version 1.0 we've only been supporting PPM RC, not PWM. We mention that in the documentation, but we should have removed the RC_TYPE parameter. That's confusing and our bad, sorry about that.

    If you've got a PWM-only receiver, we'd recommend using a standalone PPM encoder like the one here:

    Just plug the output of that into the channel 1 RC input on the Flip32. If absolutely necessary it would be possible to resurrect the code for PWM support, we'd recommend going with the encoder. Will that work for your setup?

  • Thank you very much.
    In the documentation in the site: http://docs.rosflight.org/en/latest/user-guide/rc-configuration/
    I've read that the pwm is supported. Thats why I was trying to do the connection with PWM. Is this documentation up to date? If not, where can i find a more recent one.
    Here is the text in the site:
    "Binding your Transmitter to your Receiver
    We have had the most success using PPM receivers. Parallel PWM recievers are also supported, but they actually require more effort on the part of the flight controller and can occasionally cause I2C errors."

    Do you think that it's possible to convert the signal using the raspberry pi? Thank you for the atention!

  • Oh, oops. That is the most recent documentation, looks like we updated the "Hardware setup" page, but not the "RC configuration" page. We'll get that updated, sorry about that.

    As far as converting the signal on the Pi, it's probably possible but I don't know if it'd be worth the effort. I've never really done any low-level stuff with the Pi, but as far as I can tell there's no hardware timing so you'd have to poll and write to the GPIO pins yourself which would burn CPU time and the timing may not be incredibly accurate. You could probably do it, but if it was me I'd just pick up a PPM encoder and be done with it

  • Thank you very much for the help. I've decided to buy the PWM to PPM encoder, however it will only arrive in 15 days. So, I was wondering if its possible to control the quadrotor only through the command topic, using a xbox 360 joystick controller. I've also tried to do that, but it seems that rosflight need the RC controller to work properly. The messages were properly published in the command topic, but the RC_Raw does not changed from zero.
    Is it possible to control the motors only with the joystick?
    Thank you again

  • Hi @gaprielzanoni, sorry for the slow response. Like you were saying, we have it set up so that you have to have an RC controller to arm the autopilot. While it would be possible to arm and fly only with offboard control, we have decided not to support that for safety reasons. We want to ensure that there is a way to take control and disarm the vehicle if something goes wrong with the offboard commands. Sorry you're having to wait so long for your PPM encoder!

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