QSPI with different configurations

[Den]

Hi,

I was trying to find my way configure and SRAM which has QSPI interface. However some commands are different and cannot find how to modify and adapt the qspi module to the SRAM. I started checking the forum and found this ticket:

https://devzone.nordicsemi.com/f/nordic-q-a/47129/implementing-comunication-between-a-nrf52840-and-a-qspi-memory-is37sml01g1-from-issi

The one I using is also from the same company, ISSI. Its code is: IS62WVS5128GBLL-45NLI

Moreover, we have future plans of using QSPI with SD card. I have seen post that says this is also dubious. 

As far as I understand, the adaptability of the qspi module is very limited and it cannot be used with all the chips that has QSPI interface. Is this right?

I will be more than happy if someone can please explain me this point and suggest a solution. Quick response will be very much appreciated. 

Best regards,

Denin

[Turbo J]

Den said:

Moreover, we have future plans of using QSPI with SD card.

Not going to happen.

SPI support in SD cards is single bit only - works fine with SPI and SPIM peripherials.

The 4 bit SD protocol is different and requires hardware support. Some "bigger" µCs have that but nothing in NordicSemi chips.

Den said:

However some commands are different

That also precludes QPSI peripherial usage. The magic command numbers are hard coded into the peripherial AFAIK and should be documented in the PS.

Also, external RAM is rather slow. Almost always better to use a bigger microcontroller instead, like the upcoming NRF53's.

[Den]

Thanks very much for the clarification Turbo.

I am deeply disappointed by this. QSPI should have been freely configurable just like other peripherals SPI, UART etc. It's a shame that I have not figured this out before choosing the SRAM. Totally so naive of me, I have never used QSPI before. 

Nordic Engineers please take this as an improvement suggestion for newer models. You are immensely limiting our choices of memories this way. 

Regards,

Denin

[Simonr]

Thank you for your suggestion! We're aware of this and it is up for discussion internally.

Best regards,

Simon

[Turbo J]

Note that you can still use SPIM with your RAM chip, as it support traditional SPI. SPIM3 on nrf52840 has some issues with dma memory (see errata), but can be used for fast SPI communication.