By polling the RFM69 RSSI register at rates ranging from 25us to 100us, an oscilloscope like picture can be generated for OOK signals.
This has been achieved using a RFM69 interface to a Nucleo STM32 F103RB board, and using ChibiOs V3. The RSSI register is polled with a maximum rate of 25us. The 8-bit values are stored in a circular buffer of 10000 samples. A high RSSI value is used as a trigger, after which at maximum the full buffer length will be acquired. However, a pre-time is defined (10 ms in this case), giving the opportunity to have some acquired signal before the trigger happens. After sampling has been completed, the data is printed over the serial line for further storage and graphing.
Realtime data can only be acquired with a minimum of 100us. Sending one byte per sample over the 115200bps serial ink is the limitation. This requires processing SW at the receiving side.
Code will soon be posted in github.