Inspired by recently reading an article on Hack a Day about emulating Bluetooth LE with a cheap nRF24L01+ module, I decided to take the plung and order some off eBay. I ended up spending $11.96 for ten units with shipping included, so about $1.20 per unit. More than enough extras to have some fun 🙂

My initial thoughts were to use Dmitry’s example for bit-banging BTLE, but adapt it to run on an ATMega328-PU. This turned out to be a little more difficult than I expected mainly due to (I suspect) differences between the compiler Dmitry was using and AVR GCC. For example, Dmitry’s code makes use of the cbi and abi functions. I’m not familiar with these, and a few searches revealed that they’ve been missing (deprecated then removed actually) from AVR GCC for some time. Not fully understanding the purpose of those functions either I was handicapped in my porting efforts.

I eventually found a port of this sample to Arduino and from that I was able to infer what should be done. Eventually, I ended up with this:

Unfortunately this doesn’t seem to do anything. At least, not according to iStumbler – running their Bluetooth scanner didn’t reveal any signs that my little AVR was broadcasting.

This was about as far as I was able to make it over the weekend, so I don’t yet know what the problem is. I suspect that either I’m using iStumbler wrong, or there’s something wrong with the way I ported the SPI implementation.

Either way, that’s something I’ll have to dig into later.