The RF modules RFM01 and RFM02 are cheap modules of the company Hope RF. These modules use the RF01 and RF02 chips and the ones used in this example where tuned to the 868 MHz band. The datasheets of these modules are very limited.
The receiver (RFM01) can be configured and outputs data using SPI. It can be configured with several options for data recognising and PLL, baudrate. The module has a only 16-bit data buffer. When the buffer is filled up to the defined level, the interrupt is lowered. This data can be read from the buffer using SPI.
The transmitter (RFM02) can be configured in several options like, modulation width, transmission power, bitrate. Configuration is done using the SPI, but for transmission of data the module generates a clock (connected to the external interrupt) and the microcontroller has to set the next bit on the data bit on the falling edge of this clock. To much jitter in the data response leads to data errors. When higher data rates are required, a second hardware SPI interface could be used for this.
For this demo a packet layer has been implemented, that allows packet transmission with checksums. The demo outputs the debug data via the serial port 19.2 kbaud. The serial interface is connected to the program header.
The demo contains a AVR studio project that is compiled for the atmega88, using an external crystal of 14.7456 MHz. Fuses: High byte: 0xDF, Low byte: 0x62
Also a schematic made using Eagle is added to the demo package
When making changes to this project make sure that the interrupts are not disabled (or other interrupt code is executed) for more then about 20us, otherwise this could result in data errors.
This demo is for experimental use only! It does not hold to the transmission regulations. I cannot be responsible for any damage done or other problems induced by using this code.
Datasheets (November 2010)
RF01 chip
RFM01 module
RF02 chip
RFM02 module
ATmega88
For really burning questions send an email to sjorsh, at the corresponding domain and you might receive an answer.