About coprocessor

1

Hi.

Currently, I am using pixhawk.
So, I basically want to know how to run only with main processor (cortex-m4) without coprocessor (cortex-m3).

I found several articles here.
In one article, px4fmu-v2 = FMU+IO / px4fmu-v1 = FMU. Pixhawk failsafe chip
It seems that drone may not be able to fly without cortex-m3 because cortex-m3 is reponsible for I/O operation

On the other hand, I cannot understand the aricle ( Info about px4fmu and px4io module in pixhawk - #3 by mahesh_saraswat ), but, it indicates that cortex-m3 seems only responsible for fail-safe operation when cortex-m4 is dead.

So, is it possible for pixhawk to let drone fly without cortex-m3 ?
If it requires some re-compilation, do you know how to configure that?

2

The pixhawk (px4fmu-v2) is an FMU that does most of the work (sensors, estimator, controllers, mission logic, etc), and the IO which drives the main PWMs and where the RC input is connected. If the FMU stops responding the IO can do straight manual passthru RC -> PWM. The FMU and IO communicate over serial.

The FMU also has PWM outputs, which are labelled AUX. The pixracer/px4fmu-v4 (https://pixhawk.org/modules/pixracer) is an FMU only with no IO, so it’s definitely not necessary to have both.

If you really wanted to disable the IO on a pixhawk I’d go through the init script and look at how a pixracer (fmu-v4) is started differently. https://github.com/PX4/Firmware/blob/master/ROMFS/px4fmu_common/init.d/rcS#L200
The faster/easier option is also just buying and using a pixracer. http://www.auav.co/product-p/xr-v1.htm

4

Hey,
I have been looking into the software architecture (independent of the controls) as well as the application interaction from the RC input to Motor output.
I have figured out the sensor drivers, and topics handling it.
I have figured out the mixer file for multi-rotors.
I have understood on the surface that px4io is built into a separate binary that runs on IO processor.
Also, the FMU is interacting with the i/o operations and has its own px4io driver to do so.

I would like to know, that if there is a serial communication between FMU and IO processor,
what are the different scenarios of operations and what is the interaction between them?

I have asked a broad level question!
Would like to request for a discussion

thank you

raju

5

Already answered.
@raju