RFM69 AFC failure with OOK

I observed two issues with automatic frequency correction (AFC) and OOK reception:

• The AFC value does not get cleared by switching to sleep mode and back to receive
• AFC in continuous OOK mode can yield extreme values, setting the receiver totally off-band.

AFC should not be used in continuous OOK receive mode. I am not sure whether it is designed to work in this mode (I doubt it). When signal is detected by a high RSSI, an controlled AFC may very well be to late for the OOK pulse. But even not enabling AFC in OOK imposses a risk.

When switching between FSK-packet mode for communication with the sensor network, and receiving external OOK signals, the AFC does not get resetted to zero. It can only be done by a HW-reset or power cycle, Or by explicitely clearing the AFC Value:

template< typename SPI >
void RF69A<SPI>::setThd (uint8_t thd) {
    this->writeReg(REG_AFCFEI, (1<<1));
    this->setMode(MODE_SLEEP);
    this->writeReg(REG_OOKFIX, thd);
    chThdSleepMilliseconds(400);
    this->setMode(MODE_RECEIVE);
}