[codehero]

There are two troubling lines in his code (from https://github.com/espruino/EspruinoOrion/blob/gh-pages/seri...)

  var header = sampleRate; // 1 sec to charge/discharge the cap
  var bufferSize = samplesPerByte*data.length/*samples*/ + header*2;

This implies 2 seconds of overhead per message sent from smartphone to microcontroller, 1 for the light to turn and 1 second of clearing time before the next transmission. This explains why the lights toggle so slowly.

To top it off, he uses 2 stop bits. The signalling rate may be 9600 baud but do not expect to be transmitting 9600 DATA bits a second! I think such claims need to be backed up with a demonstration full loopback capability without either side dropping a byte, with no pauses between serial bits.

[gfwilliams]

There is a demonstration there of full loopback, without the 1 sec delay. The delay is purely so you can send a command using a totally normal audio API that only uses the sound card when needed.

I could probably get away with 1 stop bit... I didn't try. To be honest if the transfer speed matters so much, it might be better to use some other means of communications :)