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]

Hi Håkon,

The second module is our custom board, with chip antenna instead of rubber duckie, but it also has PA. The max range I get is 10m with the output of -6dBm.

Regards, Sergey

[Håkon Alseth]

If they were placed close together (= 0 dBm going into the receiver, the nRF-parts may have been permanently damaged.

Do you have any more modules to test with to see if they have the same SPI-issue?

[Sergy]

Yeah have some more of these. Actually when i set the rate to 1MBPS it happens very rare (hours). But If i set the rate to 250KBPS the problem happens very fast after 1 minute of runtime.

Is there no protection at all? So what happens when i have two devices that (hopefully) would transmit with the distance of 500m between each other and then we bring them close to each other - will they just fry each other?

[Håkon Alseth]

There is protection against overvoltage and ESD. Excessive current will be an indication that the internal protection diodes inside the pads have gone off.

If the MOSI pin has been clamped high due to overvoltage, it might explain why you get 0x0F back on the MISO pin. The device will always shift back the "STATUS" register if you send "NOP" command (0xFF, ie: pin latched high).

1. Have you checked the current consumption when the devices are failing?
2. Have you scoped the SPI lines to see what goes into the nRF?

Best regards Håkon

[Håkon Alseth]

Forgot to answer the last question: If they are exposed to high RF input over time (> 0dBm) you will most likely damage the devices.

However, to ensure that you do not get 0 dBm or higher into the radio, just keep them 30 cm or so apart.