The HopeRF rfm12 is attached to the microSD port of the Ben NanoNote, which pins are exposed via an microSD card dummy adapter.
The System-on-a-chip used inside the Ben NanoNote (ingenic JZ47XX) allows us to put the microSD pins into GPIO mode, so we can create and export an SPI bus on top of them to be able communicating with the module (SPI over GPIO bitbanging).
That way there’s no need of opening the device and/or soldering anything anywhere - the module is attached directly to the microSD dummy which gets simply inserted into microSD slot of the NanoNote.
The wiring I used to get the rfm12 module working on the Ben NanoNote, and for which the provided kernel patch can be used without further adjustments, is the following.
GPIO | PIN on SD port | PIN on module | purpose / description =====|================|===============|================================= 108 | D12 (1) | MISO / SDO | SPI: master input slave output 109 | D13 (2) | nIRQ | interrupt 104 | D08 (3) | (unused) | (unused) X | VDD (4) | VDD | power 105 | D09 (5) | MOSI / SDI | SPI: master output slave input X | VSS (6) | GND (1+2) | ground 106 | D10 (7) | SCK | SPI: clock 107 | D11 (8) | nSEL | SPI: chip select
There needs to be a resistor (10-100kOhm) between pin FSK (if used) of the rfm12 module and VDD as pullup – however when just using ASK it isn’t needed anyway.