Transmit Audio Via Micro:bit Radio In MicroBlocks

Question

I am using a BBC Micro:bit version 2 and have a program set up on an editor called Micro:blocks. The code is supposed to take input from the first micro:bit's microphone and play it out of the other one's speaker. But when I try it, all I get is an annoying buzzing noise coming out the other end. I can play it correctly out of the first micro:bit only (not using radio) and it sounds fine. I can't figure out why the second micro:bit makes a buzzing noise.

With the program without radio, I messed around with how long before it played the noise, and none of the tests resulted in a buzzing noise, so I know it's probably not a timing or delay issue.

Anyways, here is my code.

Transmitting code:

when [button a] pressed
  set radio group to (7)
  set radio channel to (7)
  set radio transmit power to (7)
  digital pin write (on) to (28)
  forever
     analog pin write (microphone + 500) to (0)
     radio transmit number (microphone + 500)


when [button b] pressed
   stop other processes
   radio transmit number (0)
   analog pin write (0) to (0)

receiving code:

when program started
   forever
      if (new radio message)
         analog pin write (0) to (radio last received number)

score 0 · Answer 1 · answered Feb 11 '22 at 08:29

This is an interesting project!

Your program looks correct but the radio system may not be fast enough to send each sound sample as a separate message. As a result, you are just hearing a series of clicks, resulting in the buzzing noise.

You could check that the sound data is being sent and received by sending a second or two of sound and graphing the incoming samples on the receiving side. It will be slow, but you should see something that looks like a smooth audio waveform.

Assuming speed is the issue, you could try sending several samples in each packet by encoding them into a string. But even that may not be fast enough to create a smooth audio stream, especially since the encode/decode process will take time.

A different approach would be for the receiver to collect a second or two of sound samples in a list, then play them back in a burst. That would not provide continuous audio but might allow transmitting a sentence at a time.

Here is a record/playback project you might use as a starting point for experimentation.

Note that you can download this image and drop the .png file into the MicroBlocks IDE. MicroBlocks will read the project back from the image itself :)

Transmit Audio Via Micro:bit Radio In MicroBlocks

1 Answers1