MeArm WebControl Alpha v0.1 - For Raspberry Pi

MeArm, a little robotic arm, is controlled via a web interface on a Raspberry Pi.

How it works

A Python (Flask) web server runs in a Docker container on the Raspberry Pi. The Raspberry should preferably have HypriotOS. The arm's servos are directly connected to the 5V, Ground (GND) and GPIO pins of the Raspberry board.

1. Setup

The next sections go over the details on how the MeArm, Raspberry and software must be configured. I assume you know already the basics of the Raspberry and Docker.

1.1. Pins

First, we must wire up MeArm's servos with the Raspberry Pi. There exists different ways to do it, but here we will simply wire everything directly on the Raspberry Pi.

The control pin of the servos goes to the following respective GPIO pins (Reference here):

Grip => GPIO 17 (Green)
Elbow => GPIO 18 (Yellow)
Shoulder => GPIO 22 (Orange)
Hip => GPIO 23 (Red)

The Power (Purple) and Ground (Grey) pins from all motors can go onto a breadboard and then to the 5V pin and a Ground pin of the Raspberry. (To be validated) Alternatively, you can use a secondary power source to only power up the motors. Just make sure it's 5-6V at 2A.

1.2. Software

Note: You can connect to your Hypriot powered Raspberry Pi using pi user instead of root. Requirement: You will need your Pi to have an Internet connection to be able to pull the repository and images for docker.

Hypriot OS comes already with git installed, so just clone this repository in your home folder:

git clone https://github.com/Ra1phM/MeArmWebControl.git

Then, change directory and build the image (It will take a few minutes, relax and stretch your legs):

cd MeArmWebControl
docker build -t rpi-mearm-wb .

To start the container:

docker run --device /dev/mem:/dev/mem --privileged -p 80:5000 -ti rpi-mearm-wb /bin/bash

We launched a docker container from the image we create previously. The port 5000 from the Flask app is forwarded to port 80. -ti sends us directly in an interactive terminal inside the running container. It is very important to map /dev/mem to the container with privileged access, otherwise the container won't be able to control the pins.

Now you are in the container, to run the python app type:

python app.py

And you are done! You can access the web interface at http://<IP OF RASPBERRY PI>

1.3. Helper scripts

StartContainer.sh runs the above docker run... command.
In the container call KillServoBlaster.sh in order to switch off the MeArm. This is important since, there are sometime a bug, where the servos are somehow buzzing constantly.

Have Fun