433mhz Espruino <-> Arduino

Test sending code on Espruino side - this was what I was using for testing different training bursts. Can also just be used to benchmark signal integrity. Sends 32-bit packets - 28 bits data, 4 bits checksum. Bad checksums are rare, but not unheardof.

    var txpin=A1;

function sendCmd(add,cmd,param,ext) {
  ext=ext?ext&15:0;
    var csc=add^cmd^param;
    csc=(csc&15)^(csc>>4)^ext;
    var b=(add<<20)+(cmd<<12)+(param<<4)+ext;
    var d = digitalPulse;
    var p=txpin;
    for (i = 0; i < tp; i++) {
        d(p,1,op); 
        d(p,0,zp); 
    } 
    d(p,1,0.5); //end training burst
    d(p,0,2);
    //send 1s or 0s, and pause
    for (j=27;j>-1;j--) {
        d(p,1,((b>>j)&1)?1.1:0.6); 
        d(p,0,0.65);
    }
    for (j=3;j>-1;j--) {
        d(p,1,((csc>>j)&1)?1.1:0.6); 
        d(p,0,0.65);
    }
    // wait for finish
    d(p,0,0);
  digitalWrite(p,0);
}

function testRun(train,opp,zpp,number,interval) {
  tp=train;
  op=opp;
  zp=zpp;
  var ad=Math.round(255*Math.random());
  var pr=Math.round(255*Math.random());
  var cm=Math.round(198*Math.random());
  var ex=Math.round(16*Math.random());
  inter=setInterval("sendCmd(ad,cm,pr,ex);ad=pr=Math.round(255*Math.random());cm=Math.round(198*Math.random());ex=Math.round(16*Math.random());",interval);
  setTimeout("clearInterval(inter);",number*interval);
  setTimeout("sendCmd(31,200,150,10);console.log('done')",(number+5)*interval);
}

Test receiving code on Arduino side:

[#define](https://forum.espruino.com/search/?q=%23define) rxpin 19

int lastPinState;
unsigned long lastPinHighTime;
unsigned long lastPinLowTime;;
unsigned long lastTempHighTime=0;
unsigned long lastTempLowTime=0;
unsigned long rxdata;
int lastTempPinState;
int bitsrx;
int rxing;
int MyState;
unsigned long curTime;
int count=0;
int badcsc=0;


void setup() {
        lastPinState=0;
        lastPinLowTime=0;
        lastPinHighTime=0;
        rxdata=0;
        bitsrx=0;
        rxing=0;
        MyState=2;
	Serial.begin(9600);
}

void loop() {
        curTime=micros();
	onListenST();
}

void onListenST() {
	int pinState=digitalRead(rxpin);
        if (pinState==lastPinState) {
		return;
	} else {
              lastPinState=pinState;
        }
	if (pinState==0) {
		lastPinLowTime=curTime;
		unsigned long bitlength=lastPinLowTime-lastPinHighTime;
		if (bitlength > 1500) {
			resetListen();
			return;
		} else if (rxing==1) {
			if (bitlength > 475 && bitlength < 650) {
				rxdata=rxdata<<1;
				//Serial.print("F");
                //Serial.println(bitlength);
			} else if (bitlength > 1000 && bitlength < 1150 ) {
				rxdata=(rxdata<<1)+1;
				//Serial.print("T");
                                //Serial.println(bitlength);
			} else {
				resetListen();
				return;
			}
			bitsrx++;
			if (bitsrx==32) {
				Serial.print("Got 32 bits ");
				Serial.print((rxdata>>24)&0xFF);
				Serial.print(":");
				Serial.print((rxdata>>16)&0xFF);
				Serial.print(":");
				Serial.print((rxdata>>8)&0xFF);
				Serial.print(":");
				Serial.println((rxdata)&0xFF);
				Serial.println(rxdata);
				parseRx(rxdata);
				resetListen();
			}
			return;
		}   
	} else {
		lastPinHighTime=curTime;
                if (lastPinHighTime-lastPinLowTime > 1900 && lastPinHighTime-lastPinLowTime <2100 && rxing==0) {
                  rxing=1;
                  return;
                }
		if (lastPinHighTime-lastPinLowTime > 800 && rxing==1) {
                        Serial.println(bitsrx);
			resetListen();
			return;
		}
	}
}

void resetListen() {
        //Serial.print("end");
	bitsrx=0;
	rxdata=0;
        rxing=0;
}
void parseRx(unsigned long rxd) {
	Serial.println("Parsing: ");
	unsigned char rcvB0=(rxd>>24)&0xFF;
	unsigned char rcvCmd=(rxd>>16)&0xFF;
	unsigned char rcvParam=(rxd>>8)&0xFF;
	unsigned char rcvB3=(rxd)&0xFF;
	unsigned char rcvAdd=rcvB0&0x3F;
	unsigned char rcvExtParam=(rcvB3>>4);
	unsigned char calccsc=(rcvB0^rcvCmd^rcvParam);
	calccsc=(calccsc&15)^(calccsc>>4)^rcvExtParam;
	rcvB3=rcvB3&15;
	
	if (calccsc==rcvB3) {
                if (rcvCmd==200) {
      		    	Serial.print(count);
      		    	Serial.println(" received.");
      		    	count=0;
      		    	Serial.print(badcsc);
      		    	Serial.println(" .");
      		    	badcsc=0;
      	        } else {
      		    	count++;
      	        }
		Serial.println("Valid transmission received!");
	} else {
        Serial.print(calccsc);
		Serial.println("No good!");
        badcsc++; 
	}
}

I settled on a 20ms training burst with 0.4ms up 0.4ms down. Bit lengths were adjusted a bit from earlier to better balance the duty cycle, which might become more relevant if i was sending longer packets. I decided to structure the command as:

2 bits (reserved)
6 bits (device address)
8 bits (command)
8 bits (params)
4 bits (extended params)
4 bits (checksum)

var txpin=A1;


function sendCmd(add,cmd,param,ext) {
  ext=ext?ext&15:0;
    var csc=add^cmd^param;
    csc=(csc&15)^(csc>>4)^ext;
    var b=(add<<20)+(cmd<<12)+(param<<4)+ext;
    var d = digitalPulse;
    var p=txpin;
    for (i = 0; i < 25; i++) {
        d(p,1,0.4); 
        d(p,0,0.4); 
    } 
    d(p,1,0.5); //end training burst
    d(p,0,2);
    //send 1s or 0s, and pause
    for (j=27;j>-1;j--) {
        d(p,1,((b>>j)&1)?1.1:0.6); 
        d(p,0,0.65);
    }
    for (j=3;j>-1;j--) {
        d(p,1,((csc>>j)&1)?1.1:0.6); 
        d(p,0,0.65);
    }
    // wait for finish
    d(p,0,0);
  digitalWrite(p,0);
}

And the parserx will be:

void parseRx(unsigned long rxd) {
	Serial.println("Parsing: ");
	unsigned char rcvB0=(rxd>>24)&0xFF;
	unsigned char rcvCmd=(rxd>>16)&0xFF;
	unsigned char rcvParam=(rxd>>8)&0xFF;
	unsigned char rcvB3=(rxd)&0xFF;
	unsigned char rcvAdd=rcvB0&0x3F;
	unsigned char rcvExtParam=(rcvB3>>4);
	unsigned char calccsc=(rcvB0^rcvCmd^rcvParam);
	calccsc=(calccsc&15)^(calccsc>>4)^rcvExtParam;
	rcvB3=rcvB3&15;
	if (calccsc==rcvB3) {
		if (rcvAdd==MyAddress) {
			Serial.println("Valid transmission received!");
			//Handle the command
		} else {
			Serial.println("Wrong address - not for me");
		}
	} else {
                Serial.print(calccsc);
		Serial.println("No good!");
                badcsc++; 
	}
}

Also - what a difference an antenna makes. Just poking a dupont male jumper into that hole (no solder or anything) and letting it dangle has a huge effect on packet loss...