Digispark and nodejs - talking to the Digispark Arduino-compatible microcontroller via USB with the node-hid library

ds-duino.ino

/*
 * Accept control commands via USB.
 * 
 * Commands start with '!' and end with '.'
 * Commands have three parts: action, pin, value: !AAPPVV.
 *
 * E.g. '!01p101.' is DigitalWrite, Pin1, value = 1
 *
 * Note: This is currently *very* crude. Much improvement could be made.
 * I think the use of strncpy is eating a lot of memory. Refactor?
 */

#define START '!'
#define END '.'

#include <DigiUSB.h>

bool debug = false;

int index = 0;

char messageBuffer[12];
char cmd[3];
char pin[3];
char val[5];

void setup() {
  pinMode(1, OUTPUT);
  // Blink three times to signal ready.
  for(index = 0; index < 3; index++) {
    digitalWrite(1, HIGH);
    delay(100);
    digitalWrite(1, LOW);
    delay(100);
  }
  DigiUSB.begin();
}

void loop() {
  if(DigiUSB.available()) {
    char x = DigiUSB.read();
    if (x == START) index = 0;      // start
    else if (x == END) process(); // end
    else messageBuffer[index++] = x;
  }
  DigiUSB.refresh();
  delay(10);
}

/*
 * Deal with a full message and determine function to call
 */
void process() {
  index = 0;

  strncpy(cmd, messageBuffer, 2);
  cmd[2] = '\0';
  strncpy(pin, messageBuffer + 2, 2);
  pin[2] = '\0';

  if (atoi(cmd) > 90) {
    strncpy(val, messageBuffer + 4, 2);
    val[2] = '\0';
  } else {
    strncpy(val, messageBuffer + 4, 3);
    val[4] = '\0';
  }

  if (debug) {
    DigiUSB.println(messageBuffer);
  }

  int cmdid = atoi(cmd);

  DigiUSB.println(cmd);
  DigiUSB.println(pin);
  DigiUSB.println(val);

  switch(cmdid) {
    case 0:  sm(pin,val);              break;
    case 1:  dw(pin,val);              break;
//    case 2:  dr(pin,val);              break;
    case 3:  aw(pin,val);              break;
//    case 4:  ar(pin,val);              break;
    case 99: toggleDebug(val);         break;
    default:                           break;
  }
}

/*
 * Toggle debug mode
 */
void toggleDebug(char *val) {
  if (atoi(val) == 0) {
    debug = false;
    DigiUSB.println("goodbye");
  } else {
    debug = true;
    DigiUSB.println("hello");
  }
}

/*
 * Set pin mode
 */
void sm(char *pin, char *val) {
  if (debug) DigiUSB.println("sm");
  int p = getPin(pin);
  if(p == -1) { if(debug) DigiUSB.println("badpin"); return; }
  if (atoi(val) == 0) {
    pinMode(p, OUTPUT);
  } else {
    pinMode(p, INPUT);
  }
}

/*
 * Digital write
 */
void dw(char *pin, char *val) {
  if (debug) DigiUSB.println("dw");
  int p = getPin(pin);
  if(p == -1) { if(debug) DigiUSB.println("badpin"); return; }
  pinMode(p, OUTPUT);
  if (atoi(val) == 0) {
    digitalWrite(p, LOW);
  } else {
    digitalWrite(p, HIGH);
  }
}

/*
 * Digital read
 */
/*
void dr(char *pin, char *val) {
  if (debug) DigiUSB.println("dr");
  int p = getPin(pin);
  if(p == -1) { if(debug) DigiUSB.println("badpin"); return; }
  pinMode(p, INPUT);
  int oraw = digitalRead(p);
  char m[7];
  sprintf(m, "%02d::%02d", p,oraw);
  DigiUSB.println(m);
}
*/

/*
 * Analog read
 */
/*
void ar(char *pin, char *val) {
  if(debug) DigiUSB.println("ar");
  int p = getPin(pin);
  if(p == -1) { if(debug) DigiUSB.println("badpin"); return; }
  pinMode(p, INPUT); // don't want to sw
  int rval = analogRead(p);
  char m[8];
  sprintf(m, "%s::%03d", pin, rval);
  DigiUSB.println(m);
}
*/
void aw(char *pin, char *val) {
  if(debug) DigiUSB.println("aw");
  int p = getPin(pin);
  pinMode(p, OUTPUT);
  if(p == -1) { if(debug) DigiUSB.println("badpin"); return; }
  analogWrite(p,atoi(val));
}

int getPin(char *pin) { //Converts to P0-P5, and returns -1 on error
  int ret = -1;
  if(pin[0] == 'P' || pin[0] == 'p') {
    switch(pin[1]) {
      case '0':  ret = 0; break;
      case '1':  ret = 1; break;
      case '2':  ret = 2; break;
      case '3':  ret = 3; break;
      case '4':  ret = 4; break;
      case '5':  ret = 5; break;
      default:             break;
    }
  } else {
    ret = atoi(pin);
    if(ret == 0 && (pin[0] != '0' || pin[1] != '0')) {
      ret = -1;
    }
  }
  return ret;
}

ds-node-test.js

var HID = require('./build/Release/HID.node');

var device,ds,char;
var devices = HID.devices(0x16c0, 0x05df); // look for digisparks

if (devices.length > 0) {
  console.log(devices);
	console.log('Attaching to first entry.');
	device = devices[0];
	console.log('USB Path:', device.path);

	ds = new HID.HID(device.path);

	ds.setNonBlocking(1); // blocking is bad, mkay?

	ds.write(new Buffer("!990011.")); // turn debug on

	console.log('analogWrite P1 25...');
	var cmd = "!03p125.";
	// Buffer is an array of bytes, like write() wants.
	ds.write(new Buffer(cmd));


	while (1) {
		var buff = new Buffer(ds.getFeatureReport(0,254));
		console.log("using getFeatureReport: ", buff.toString());
		if (! buff.length) break;
	}

	console.log('analogWrite P0 45...');
	cmd = "!03p245.";
	// Buffer is an array of bytes, like write() wants.
	ds.write(new Buffer(cmd));

//*
	ds.read(function(err, data){
		if (err) {
			console.log("Error! ", err);
		} else {
			console.log("using ds.read: ", data);
		}
	});
//*/
//**/	ds.read(onRead);

} else {
	console.log('No Digispark found.');
}

function onRead(err, data) {
	if(err) {
		console.log('Err! :-(');
	} else {
		if (1 || data.length) {
			console.log('DATA: ' + data);
		}

		ds.read(onRead);
	}
}

I think the use of strncpy is eating a lot of memory. Refactor?

I agree.
Why don't you just move pointers around?

Does the DigiUsb require a \0ed string?

In that case why don't you change the protocol to: AA\0PP\0VV\0
Also, what happens if I want to write to pin 11 ?

This way you can use non fixed length messages.
If you don't like the \0 as tokenizer you could use something else like | and then strtok that will return pointers and replace the token with \0 for you :)

Yes, this code is still in a crude state of hackage from @ecto's original version, because I was trying to get it to fit in the Digispark's 6K available flash. But I haven't refactored it yet to actually handle command parsing in a more sane way. For one thing, I could whittle down the command and pin parameters to a single character each. I might also be able to get the value as a single raw byte, and just put the onus on computer at the other end of the USB connection to package the data accordingly.

There might be a good case here for a tiny module on the node side to provide convenience functions for packing/unpacking the data packets.

It's just one of those things to work on in my "Copious Free Time".

Hi Dougal,
what is your status on this?

hi dougal,

looks cool.

this would be cool solutions for the digispark.

i am now trying to run you programm with digitspark but without success.
which drivers for the digispark have you used on windows?
I have tried serveral without success. with the digiusb monitor.exe it works.

can you post the binary node-hid module?

i can compile it with gyp but can find a lot usb devices but not the digispark.

thanks,
alex

Hey what drivers did you use for this? node-hid doesn't pick up the device...

loop() function is not working this part of code giving me error