Monday, November 23, 2015

Network Servo Control Demo

Now that my WebSockets libraries are working better, I decided to try to use them in a program which can control a Servo.

To make the demo more interesting, I strapped a webcam to the top of the servo so I could use it like a DIY security cam.

The servo controlling software opens a WebSocket port to listen for incoming messages.  For now, the messages are simple -- A number, which represents the percent of range of motion of the servo.

So if you send 50, that means 50% of the range of motion, and the program will instruct the servo to move there.

To send messages to the servo controller, I use a super simple program written to bridge stdio to WebSocket connection, basically a WebSocket 'telnet'.  This is my wsEndpoint program.

Feeding into the wsEndpoint is stdio, but now controlled by a 'tk' gui program showing the numbers 1-100.  Click the number, it prints the number to stdout, which is relayed over the WebSocket connection, and the servo moves.

In the screenshot above you can see a washed-out square image on the screen, that is the grid of numbers.

The webcam in this demo is hooked up to my laptop, not the Pi.  No WebRTC involved here.

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