As mentioned in part 3, I bought a ready-made RF module off Ebay – the MRF89XAM8A-I/RM which arrived yesterday. It is the 868MHz version so should be ideal for driving the Xyloband. I’ve coupled it to a PIC16F1789 8-bit microcontroller from Microchip. I’ve written some C code (using the XC8 compiler) that configures the SPI interface between the two units. Various bytes are sent to the RF module to initialise it before moving into the transmit phase where I’ve programmed a random pulse pattern to be transmitted. The SPI interface appears to be working fine (based on oscilloscope traces).
I’ve taken the first back off the Xyloband and powered it from the 3.3v supply – the batteries in the Xyloband are AAAA so I’ll have to track down a supplier of those later. They are a few mm shorter than AAA and about 2/3 of the diameter.
Currently the Xyloband doesn’t light (apart from briefly when power is connected). The current consumption from my PSU also doesn’t imply any significant RF transmit. The only other piece of ‘test kit’ I have is an old radio scanner – tuning this to 869.5MHz doesn’t show any power on the VU meter.
I’ll have to re-read the datasheet on the MRF89XAM devices – I’m sure I’ve forgotten to set one of the registers correctly. My aims are to:
(1) Get the module to Tx at the required frequency
(2) Play with the output pattern until the Xyloband lights up….and replicate some of the Coldplay magic !