It seems that all the copycat tutorials on doing this also need a parallel port adapter. The process involves building an LPT (parallel port) adapter which then bitbangs the SPI communication to the chip. And software can be pirated.įrom what I can make out the first person to realize this (or at least the first to write on the internet about it) was Robin Gross, whose site is called Byron's Blog. What makes the RN-42 more feature filled, and thus more expensive, is the software it's running. The thing is, under that shielding, the RN-42 uses virtually identical hardware to the HC-05, and its main chip (the CSR BC417) is the same.

Here's a picture from the internet of an RN-42 module, a far more advanced bluetooth module, which costs over £20: The HC-05 module is a bluetooth serial adapter and this one cost me £2.03: Part two builds an example wireless gamepad with the result. Part one explains how to load an HC-05 module with the firmware from the RN-42 without the need for a parallel port programmer. This project draws hugely on the work of other people.