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

[Sergy]

Håkon,

i did some additional testing. SPI works correctly on the MCU side, so it sends correct data. I have a feeling that indeed when devices are too close by to each other it stops working. Any idea on how to protect it from a high-power signal? 30cm apart is not enough especially if we use the highest power.

Regards, Sergey

[Håkon Alseth]

Since the nRF24L01+ does not have an RSSI, it is not trivial to implement a detection of this. You could use the RPD bit (detects if signal is > -64 dBm) to adjust the output power, by checking this bit when you receive an ACK.

Best regards Håkon

[Sergy]

Well checking for -64 dBm wont really help, because it wont say anything about how much over -64 the signal power is. May be there is some hardware solution? Like installing a blocking diode for the RX?

[Håkon Alseth]

The problem is that you will then degrade the receiver sensitivity as well, which affects your overall range. I would recommend that you use a lower output power instead of doing this.

You could try a power-output scaling based on the number of re-transmissions that occurs. If you have a low re-transmit count, then you scale the output power down. When it rises, you set higher output power.

Best regards Håkon

[Sergy]

The thing is that we dont use re transmits at all to maximize the bandwidth. But what I meant is to use diode on the incoming signal so if signal is over 0dBm diode would cut it down to 0 dBm, here is the diode im talking about: www.infineon.com/.../bat24-02ls.pdf

Thanks!