Use a rs485 communication module

Good enough :)

Ok, it looks like you don't need anything fancy at all. Just use the standard hardware serial.

• Find a USARTx_TX pin on your board's pinout page (linked from here): http://www.espruino.com/Reference#boards
  

• If it was USART1, do something like:

  Serial1.setup(19200,{tx:TX_ENABLE_PIN});
  
  function sendData(data) {
  digitalPulse(TX_ENABLE_PIN,1, (data.length+1)*10/19200);
  Serial1.write(data);
    
  }
  
  sendData([0x80,0x87,0xFF,0x7F,0x7F,0x7F,0x7F,0x7F­,0x7F,0x7F,0x8F]);
  

That should all work ok - it's a bit fiddly because you have to set the TX enable pin on RS485, but not the end of the world.