Robot Arm Controller

3D printed robot arm, controlled with a Raspberry Pi Pico.

The docker container that the code is compiled in was created by lukestep, for more instructions view his repo.

Run the following command in the repos root directory

docker run -d -it --name pico-sdk --mount type=bind,source=${PWD},target=/home/dev lukstep/raspberry-pi-pico-sdk:latest

I have forked the lukestep's repository and added some more tools. To use that instead clone the repo and the build it.

git clone https://github.com/Anton-Augustsson/raspberry-pi-pico-docker-sdk.git
cd raspberry-pi-pico-docker-sdk
docker build . --tag pico-sdk

Cd into robot-arm-controller and run.

docker run -d -it --name pico-sdk-aa --mount type=bind,source=${PWD},target=/home/dev pico-sdk:latest

Compile

You have two options: either you run with the pico library or you use the simulation flag. So that you may run without hardware. You are thus able to change the environment through software.

To run with hardware run:

rm -r build && mkdir build && cd build
cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=1 ..  # or cmake ..
make -j4  # or make

Then you have to move the .uf2 file to the pico when it is in boot mode so it can be mounted.

To run with simulation run:

rm -r build && mkdir build && cd build
cmake -DSIMULATION=ON ..
make
./sample

PWM

Controlling the motors on the robot arm is done my sending a pwm signal to the motors on the robot arm.

Motor	PWM function	Header Pin	Broadcom pin name
MG996R	PWM	4	GP2
MG996R	PWM	5	GP3
MG996R	PWM	6	GP4

There are two models of motors used for the robot arm.

Model	PWM Period	Voltage
SG90	50Hz	5V
MG996R	50Hz	5V

Framework

Framework is a separate program to experiment the general program structure of a microcontroller. SPI will be used to communicate with a bare metal controller and a node.

SPI

• SCLK: Serial clock
• MOSI: Master Out Slave In; SDI: Serial data in
• MISO: Master In Slave Out; SDO: Serial data out
• CE0: Chip enable 0
• CE1: Chip enable 0

Rassbary PI Pico (Slave/Peripheral)

SPI function	Header Pin	Broadcom pin name	Broadcom pin function
MISO	25	GP19	SPI0 TX
SCLK	24	GP18	SPI0 SCK
CE0	22	GP17	SPI0 CSn
MOSI	21	GP16	SPI0 RX
From Communicating as master and slave via SPI

Rassbary PI 4 (Master/SPI controller)

SPI function	Header Pin	Broadcom pin name	Broadcom pin function
MOSI	19	GPIO10	SPI0_MOSI
MISO	21	GPIO09	SPI0_MISO
SCLK	23	GPIO11	SPI0_SCLK
CE0	24	GPIO08	SPI0_CE0_N
CE1	26	GPIO07	SPI0_CE1_N
From link.
From link.

Requirement

For src you need to install (nlohmann/json)[https://github.com/nlohmann/json/tree/develop?tab=readme-ov-file#integration], which you can do with vcpkg.

Resources

• Step 1: A Basic Starting Point
• Google C++ Style Guide

PICO SDK

• Raspberry Pi Pico C/C++ SDK
• Getting started with Raspberry Pi Pico
• Making Two Raspberry Pi Pico Boards Communicate through SPI using C/C++ SDK

Linux driver for SPI peripheral

• SPI – Serial Peripheral Interface Protocol Basics
• Linux Device Driver Tutorial – Part 1 | Introduction
• Serial Peripheral Interface (SPI)
• Device Tree for Dummies