PX4FMU(V1) takeoff/general problems

PX4 Autopilot
1

Hi all,

I’m relatively new to the px4 community and have found myself with a few confusing problems. I am working with a generic “x” quad build and a px4fmu(v1.7) standalone. I have been relatively successful in the general set up of the vehicle (via micro SD card - things like the config. file, etc.) but I am having a difficult time when I go to fly the quadrotor.

The problems first start with qgroundcontrol (v 2.8.0) and flashing firmware to the fmu. When I go to flash the firmware, the bootloader recognizes the px4fmu, tells me how much “flash” is available and then proceeds to just “sit there” until I unplug the USB cable. I was able to flash firmware with an older version of qgroundcontrol, but not with this most recent update. Additionally, if I attempt to flash “custom” firmware (px4fmu-v1_default, etc.); I am not able to flash px4fmu-v2_default. Instead, the terminal begins repeatedly printing that it found device and never erases/flashes the new firmware - I am, however, successful with flashing px4fmu-v1_default - is this a problem or is this behavior correct?

Regardless of my possible firmware problem, my main issue is with attempting to fly the quadrotor. I have double (even tripple) checked the hardware, rotor configuration/numbering and rotational directions as well as ensuring that the px4fmu is calibrated and displaying the correct artificial horizon. However, when attempting to takeoff, the vehicle always flips. I am trying to fly the vehicle through a USB controller and qgroundcontrol, but with no luck. I can see that the commanded pwm outputs from the px4 (through the analyze widget in qgc) do not seem correct. The chip will often command non-symmetric pwm outputs when in manual mode and I have, overall, had more success in attempting to control the quad when enabling ACRO mode - although even this mode does not give me total control of the throttles. I have been able to “tether” the quad and see that the roll, pitch and yaw commands seem to work 100% correctly when in ACRO mode (even manual mode), but not the throttles (I cannot get them below a pulse width of 1500 micro seconds). I have looked around quite a bit for solutions to this/these problems but haven’t been too successful in finding a general solution that would work for me. Does anyone know of any possible solutions/experienced similar issues to this with a px4fmu?

Thanks in advance,

-Daniel

2

Hi Daniel,

The PX4FMU that you are using is referred to as px4fmu-v1_default when building. The target px4fmu-v2_default is for the Pixhawk hardware.

Considering the controls and PWM issues, I’m wondering which airframe you have selected in QGroundControl? And have you done the RC calibration?

3

Julian,

Thank you for your reply! I have set the airframe to “generic quadrotor X config”. I believe that I may be having an ESC calibration issue, as there have been times that I cannot hear a difference between when the FMU is outputting 1500 microsecond pulse vs. a 2000 microsecond pulse. Additionally, it does not seem that, with the config.txt file that I posted previously, that the pwm ports are being configured correctly - the ESC’s do not always make the “singing” noise when plugging in the battery - do you have any idea what may be going on? Any time I attempt to calibrate the ESC’s with qgroundcontrol I get a “time out waiting for bat” error - even if I have plugged my battery in. I have attempted to calibrate with the “nsh” prompt, but to no avail.

As for the RC calibration issue - I am using a USB joystick to manually control the quad. I have set it up through qgroundcontrol (v2.8) and been relatively successful in seeing that my inputs seem to be functioning - even though qgroundcontrol does not always discover the joystick, but the times it does (and the quad initializes correctly) I can get close to controlling it with manual flight (but these cases seem to be relatively spontaneous) - but I think there is some sort of esc calibration error that I’m not sure how to sort out - any ideas?

Thanks again for all the help,

  • Daniel
4

Julian,

my apologies for not including my config file. It looks like the following (set on the SD card):

set VEHICLE_TYPE mc
set USE_IO no
set MIXER quad_x
set FMU_MODE pwm
set PWM_OUT 1234
set PWM_MIN 1000
set PWM_MAX 2000
set PWM_DISARMED 900

these lines of code are in a file on the SD card labeled config.txt

although, I have been looking around and it looks like I may be able to do most of this in extras.txt, which is a text file that I am currently not using.

Thanks again,

-Daniel

5

I would suggest to try the following: remove all lines with “set PWM_…” in config.txt, therefore use the default Quad X PWM settings. Then do the ESC calibration in QGroundControl, and try again.