nrf52840 QSPI single byte/word access

[Andrew_Engineer]

Hello,

we are would like to drive 3 shift registers simultaneously using QSPI interface. We have look through QSPI examples but it looks like all examples are build around QSPI flash.

We would like to have an ability to send 3X16 or 3X8 bit words over QSPI port ie each data line to data In of shift registers and all 3 shift registers are clocked from SPI clock.   

Can please advise which API/functions can be used?

Thank you for your support.

Regards,

Andrew.

[tesc]

Hi,

It is correct that all QSPI examples show QSPI flash, as external flash is the reason why we included the QSPI peripheral. It is not intended for other uses.

What is your use case, does the SPIM peripheral not cover your needs?

Regards,
Terje

[Andrew_Engineer]

Hi Terje

Thank you for your replay. main reason why we are looking towards QSPI vs SPI is ability to simultaneously writhe to 3 channels, utilizing 3 data lines out of 4.  main reason behind it  is speed.

If there is a way to get byte/word access to QSPI ie by bypassing API and accessing MCU registers directly?

please advise.

Regards,

Andrew.

[tesc]

Hi,

The registers are as specified in the nRF52840 Product specification, and although not recommended you are free to access them directly instead of using our drivers. Note however that in that case support may be limited and we expect you to know more about what you are doing. I am not sure if it will give you what you need, but if you think so you are free to try it out and experiment.

Note that there are four SPIM peripherals, where the maximum frequency is 32 MHz for one of the peripherals (SPIM3) and 8 Mbps for the three others (SPIM0-2). I doubt using the QSPI peripheral will be much faster, if at all possible. Execute in place (XIP) for the QSPI peripheral rates at 8 MHz for 16 bit instructions and 4 MHz for 32 bit instructions.

Regards,
Terje