Custom Function in MATLAB

passas · December 20, 2018, 10:12am

Hi,

Since I couldn't find a way to change the frequency of PWM output in MATLAB, I want to write my own function in MATLAB. But I couldn't find a reliable source to get help.

Is there a way to write my own function to control Arduino's output in MATLAB?

Thanks!

ron_sutherland · December 21, 2018, 3:20am

An Arduino Uno is an ATmega328p, you may want to have a look at the datasheet.

https://www.microchip.com/wwwproducts/en/ATMEGA328P

It is a microcontroller that has an AVR core with some peripherals.

The PWM pins are done with output compare registers that cause modulation when some control bits are set correctly. Arduino has abstracted this for you into what they call analogWrite()

https://www.arduino.cc/reference/en/language/functions/analog-io/analogwrite/

The way this abstraction works can be seen

github.com

arduino/ArduinoCore-avr/blob/b7c607663fecc232e598f2c0acf419ceb0b7078c/cores/arduino/wiring_analog.c#L104

    
      
          #endif
          
          
	// combine the two bytes
          	return (high << 8) | low;
          }
          
          
// Right now, PWM output only works on the pins with
          // hardware support.  These are defined in the appropriate
          // pins_*.c file.  For the rest of the pins, we default
          // to digital output.
          void analogWrite(uint8_t pin, int val)
          {
          	// We need to make sure the PWM output is enabled for those pins
          	// that support it, as we turn it off when digitally reading or
          	// writing with them.  Also, make sure the pin is in output mode
          	// for consistenty with Wiring, which doesn't require a pinMode
          	// call for the analog output pins.
          	pinMode(pin, OUTPUT);
          	if (val == 0)
          	{
          		digitalWrite(pin, LOW);

Now if you want MATLAB (or any Windows/Mac/Linux program) to access those functions you have to write an Arduino program that runs on the ATmega328p and exposes the desired functions in a way that MATLAB can interface (e.g. over the serial port).

system · May 6, 2021, 11:34am