NRF52840 CKAA does not see the recommended pins for QSPI/CSN？

[eview]

NRF52840 CKAA does not see the recommended pins for QSPI/CSN？ Is it P0.18?

[Hung Bui]

Hi Terrel, 

If you have a look here, you can find the suggested pin for QSPI on WLCSP chip (CKAA)
I don't think P0.18 is recommended. 

[eview]

Yes I had a look .But I can't find the QSPI/CSN. I can find the pin for QSPI/CSN on QIAA  chip 

[eview]

Which pin is QSPI/CSN on the CKAA Chip?

[Hung Bui]

Hi Terrel, 

CSN is not a high frequency signal in QSPI, it's the chip select pin. It only go low when the QSPI is active for the peripheral and go high when finish. So it's not very important, you can choose any GPIO pin for it. I would suggest to choose one of the pin NOT suggested for QSPI because you have only 5 pins that are suggested for QSPI. Preferable to choose the pin that doesn't say "low frequency only".

The most important thing is that you use the correct QSPI SCK, it has the highest frequency. Next are the IO0-IO3. These pins have to be in the list of suggested QSPI.