SPI returns 0x0F on any request after random period of time

[Sergy]

Hi, im using nRF24L01+ to constantly transmit data and all working fine, but at some point SPI fails and the only returned values I get are 0x0F - doesnt matter which register I try to read or write. Any idea why is that happening?

Thanks, Sergey

[Håkon Alseth]

Hi,

If you have "Dynamic Payload Length" enabled (en_dpl in FEATURE register, and "DYNPD" register), the state machine inside the nRF24L01+ can go into a unknown state if you receive a packet which is of length = 0 || length > 32 bytes. I have not seen SPI transaction byte errors in this state, but I have seen the RX deadlock situation.

What you can do to prevent this is to add a check for your payload length:

void radio_isr()
{
....
len = read_reg(R_RX_PL_WID);
if (len == 0 || len > 32) 
  flush_rx_fifo();
else 
  read_out_payload(&my_payload);
....
}

Best regards Håkon