Controlling Arduino through MATLAB?

Question

I had a Roboteq motor controller, but it wasn't fast enough. I'm hoping Arduino will be faster.

Supposing that the transfer is fast enough for my purposes, how can I read angular velocity, given that I have an encoder? Honestly, I'm not totally sure how to hook it up to an Arduino board. I can't find a name for my encoder... This is the datasheet though.

Can anyone help me with how to hook it up, and what commands to use in MATLAB?

Thanks.

Answer 1

Do all the processing on the Arduino, and supply the results to Matlab over serial.

I'm not 100% sure about your particular encoder, but generally encoders talk in "Grey Code". This is a series of bits which allow you to know the direction the encoder has turned.

There are a number of libraries and tutorials for Arduino dealing with encoders.

• http://playground.arduino.cc/Main/RotaryEncoders

• http://www.hobbytronics.co.uk/arduino-tutorial6-rotary-encoder

The one I use comes from here:

• http://www.pjrc.com/teensy/td_libs_Encoder.html

It would be best to use a library with interrupt routines on pins 2 & 3 (these support external hardware interrupts), so whenever the pin gets a signal from the encoder, the Arduino can act on it immediately. If you do not use these pins, and have time-consuming processing in the loop(), it's easy to miss 'ticks' from the encoder.

#include <Serial.h>
// Rotary Encoder (Interrupt Driven)
#define ENCODER_PIN_A 2 /* must be pin2 for interrupt */
#define ENCODER_PIN_B 3 /* must be pin3 for interrupt */
#define ENCODER_OPTIMIZE_INTERRUPTS
#include <Encoder.h>
Encoder encoder(ENCODER_PIN_A,ENCODER_PIN_B);
void setup()
{
 Serial.begin(115200);
 // Gentlemen, start your encoders
 pinMode(ENCODER_PIN_A,INPUT_PULLUP);
 pinMode(ENCODER_PIN_B,INPUT_PULLUP);
}
void loop()
{
 unsigned long start_time = millis();
 Serial.println("Dear Matlab...");
 while (1)
 {
 unsigned long now = millis();
 unsigned int encoder_value = encoder.read();
 // Do whatever angular velocity processing is needed here
 unsigned long ticks_per_ms = encoder_value / (now - start_time);
 // Send the result back to Matlab
 Serial.println(ticks_per_ms,DEC);
 }
}

I think for your encoder the "A" and "B" outputs are where the grey code will be coming from. These would be connected to Arduino pins 2 & 3.

Obviously the code above is not a complete solution, and needs to take care of edge-conditions like overflow of millis() after some time, etc. etc.

• TechnoSam: Hmm... Interesting. Do you know how many iterations per second that could run? I'm just afraid that a serial connection would be too slow. Could I do it over USB somehow?
• Kingsley: 115200 baud gives you over 10,000 bytes per second.