Building an autopilot from scratch using a RaspBerryPi Zero : Mini Zee

JAR4x4 · December 13, 2018, 8:17pm

Thanks for the tip, but I’m not that into the code yet… I found that the PCA address is defined here:

ArduPilot/ardupilot/blob/master/libraries/AP_HAL_Linux/RCOutput_PCA9685.h#L7


#pragma once


#include <AP_HAL/I2CDevice.h>


#include "AP_HAL_Linux.h"


#define PCA9685_PRIMARY_ADDRESS             0x40 // All address pins low, PCA9685 default
#define PCA9685_SECONDARY_ADDRESS           0x41
#define PCA9685_TERTIARY_ADDRESS            0x42
#define PCA9685_QUATENARY_ADDRESS           0x55
#define PCA9685_QUINARY_ADDRESS             0x61


namespace Linux {


class RCOutput_PCA9685 : public AP_HAL::RCOutput {
public:
RCOutput_PCA9685(AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev,

This is the same address that pi@raspberrypi:~ $ sudo i2cdetect -y 1 displays…

Has anyone tested that this code works?:

github.com

ArduPilot/ardupilot/blob/fbf072d84be9e54ee9973309ac0bfc9c7d882981/libraries/AP_HAL_Linux/HAL_Linux_Class.cpp#L179


static RCOutput_PRU rcoutDriver;
#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BBBMINI || \
     CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BLUE || \
     CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_POCKET
static RCOutput_AioPRU rcoutDriver;
/*
 use the PCA9685 based RCOutput driver on Navio and Erle-Brain 2
*/
#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_ERLEBRAIN2  || \
     CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_PXFMINI
static RCOutput_PCA9685 rcoutDriver(i2c_mgr_instance.get_device(1, PCA9685_PRIMARY_ADDRESS), true, 3, RPI_GPIO_27);
#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_NAVIO
static RCOutput_PCA9685 rcoutDriver(i2c_mgr_instance.get_device(1, PCA9685_PRIMARY_ADDRESS), true, 3, NAVIO_GPIO_PCA_OE);
#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BH
static RCOutput_PCA9685 rcoutDriver(i2c_mgr_instance.get_device(1, PCA9685_QUATENARY_ADDRESS), false, 0, RPI_GPIO_4);
#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_DARK
static RCOutput_PCA9685 rcoutDriver(i2c_mgr_instance.get_device(1, PCA9685_QUINARY_ADDRESS), false, 0, RPI_GPIO_27);
#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_ZYNQ || \
     CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_OCPOC_ZYNQ
static RCOutput_ZYNQ rcoutDriver;
#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BEBOP

@ppoirier is there any chance you still have the arducopter binary you compiled for your project still?

I tried to compile from the Erle fork, but it seems the waf code is broken in their fork

ppoirier · December 13, 2018, 9:16pm

Well. I might try building it , where did you get your RT kernel ?
What cross compiler are you using for the RPI Zero ?

JAR4x4 · December 13, 2018, 10:33pm

I followed this tutorial for the RT kernel:

You need to add the following to the first line in cmdline.txt, for USB to work:
dwc_otg.fiq_fsm_enable=0 dwc_otg.fiq_enable=0 dwc_otg.nak_holdoff=0

I have used the regular tools provided by raspberry:

ppoirier · December 14, 2018, 12:10am

@JAR4x4 Pretty good blog
I will dust off the pxfmini during xmas break , hook-up to a RPI Zero and build new image
Unfortunately, I did not kept any copy of old image.

JAR4x4 · December 14, 2018, 7:09am

Awsome, thanks!

Can it be that the problems are related to kernel 4.14?

I will try anyways with an older raspbian version and se if that helps.

Any other advice on how I can try to debug this issue?

SevTD · January 3, 2020, 1:09pm

Hi guys,

Sorry to Bring An old post back to life. I am looking for a pxfmini for my raspberry Pi zero. Apparently Erle has gone out of business. It seems like the topic starter has the diagram info for this Autopilot. Would you be kind enough to share this with me? A colleague of mine makes circuit boards so he could build it for me.

Kind regards and a happy 2020!

ppoirier · January 3, 2020, 2:52pm

OMG… this is quite old stuff
Problem is that code is not up to date , it is not maintained and it is not stable.
I dont have electronic copy of the schematics.

Alternatively, You may look at this:

Lance_N · April 12, 2020, 12:03am

Hopping into this thread…
The build page you linked takes no code from the the Erle site- would this then mean that it would still be stable?

ppoirier · April 12, 2020, 12:42am

Hello
Patching the new kernel for RT could be challenging
Other issue is the PWM RCIN as the DMA is not working properly with latest releases , that is not a problem if you are using a serial type of receiver , but then you are out of available serial for telemetry and GPS

Lance_N · April 13, 2020, 2:44am

Ahh…
Thanks for the info. I’ll be promptly switching back to the F7 train now.

playertr · April 15, 2020, 4:06am

Hi Lance and Mr. Poirier,

A word of warning if you ever end up using a PCA9685 without an external clock: per page 14 of the datasheet, the bit that turns off the internal clock is a “sticky bit” meaning that the device must be power cycled before it can be be cleared. This led me to think that my changes to the code weren’t working when actually, changing the external_clock Boolean to false didn’t affect the state of the device until I powered it off.

Good luck with your F7!