Communicating with multiple Espruino devices

Yes - neither I2C or SPI slave is implemented because you need to have very fast, guaranteed response times to do it properly (which is almost impossible with JS).

However, Serial is a really good option. Set the TX pin of each slave to pinMode(TX, 'af_opendrain'), then connect all the boards together and have a pullup resistor on the slave TX (master RX) line.

You can make your own addressing system, but actually it is possible to use Espruino's built-in console. For instance:

• Connect all slave B6 together, with a 4.7k pullup resistor to 3.3v, and to the master B7
  
• Connect all slave B7 together, to master B6
  
  

Slaves

pinMode(B6, 'af_opendrain');
var ID = "slave1"; // or whatever

function myFunction() {
}
function onInit() {
  echo(0);
}

Master

function cmdOnSlave(slave, cmd) {
  Serial1.println("if(ID=='"+slave+"')"+cmd+";");
}

cmdOnSlave("slave1", "myFunction(1,2,3)");
cmdOnSlave("slave2", "digitalWrite(LED1,1)");