Well I received my RN-52, got it all soldered up, and hooked up to my laptop for the initial setup. Once I figured out that I needed to hit enter after entering a command, I got everything set to start streaming music from my phone.
Fantastic. Wait, the sound quality is kind of… wrong. I check the connections to the trrs breakout, everything looks good. Nope. Wait a moment. Flip the connections around. That’s better. Not fantastic though. And now the Bluetooth chip is flaking out if I run at full volume. Perhaps my power supply isn’t running enough current to the chip. No, that’s not it. I eventually gave up on that and tried test calls to see if the audio was OK. Unfortunately not. I have no audio coming through the microphone. Well tits.
So after a couple months with it just sitting there, I noticed that Sparkfun released a new bluetooth chip. The BC127. So I ordered that. When that one arrived, I did the same thing. Soldered everything up, wired it up to the computer, set everything to start streaming music. Fantastic, this one doesn’t crash when I run it at full volume. However, the audio quality isn’t as good as the RN-52. That’s fine, I’ll build an equalizer or something, but at this point, that’s far into the future. And this chip also passes the MP3 metadata through serial. Great, so now I can display the track information on a screen. Fantastic.
When I try to make a call, however, I get the same problem. There is no audio coming through the microphone. This time I did a little more research. I found out that I’m not building the circuit correctly, and I need to put a few more components between the microphone and the chip. Balls. And I can’t for the life of me figure out what I’m missing. I’ve picked up an electret microphone with a built in amplifier, but it’s not working either. This is seriously pissing me off now. Doing a search for electret microphone biasing returns so many different results depending on what you are attempting to do, that I can’t make heads or tails of it.
So I’ve put the project on hold while I learn more circuit building. We’ll see if I can figure this out eventually. If not, I have two chips to build a music box out of.