Questions: QSPI driver for an external flash with the nRF5 SDK 17.1, nRF52840

[xxb9075]

Hi guys,

We designed a custom board with the nRF52840 SoC and is trying to use the QSPI interface to communicate with an external flash AS5F18G04SND-10LIN.

We are having some questions here and hope to get some feedback:

1. The nRF52840 datasheet recommended the following pins for QSPI communications (aQFN73 package): p0.18 for CSN, p0.19 for SCK, p0.21, p0.23, p0.22, p1.00 for SIO. While our current design used p0.25 for CSN, p0.22 for SCK, p0.20, p0.21, p0.23, p0.24 for SIO. Is this a problem?

2. I'm trying to build the driver for the external flash we used: AS5F18G04SND-10LIN, starting from the peripheral/QSPI example from the nRF5 SDK, I'm not sure if I fully understand the example though. In the example, the application code called the nrf_drv_qspi_erase, nrf_drv_qspi_write, and nrf_drv_qspi_read functions to erase, write and read the flash. However, from the datasheet of the external flash (MX25R6435FZNIL0) used on the nRF52840 DK, a device operation should start with a command byte (for example, page program would be 0x02). I don' see how these commands are implemented in the example.

3. Can I have some top-level advice on how to build the driver for AS5F18G04SND-10LIN? Like, what should the program flow be like?

Thanks so much for your time guys!

Best,

Richard

[Jørgen Holmefjord]

Hi,

1. We would recommend you to use the pins from the PS if possible, but other high-frequency GPIOs should work as well if you are not able to use the recommended GPIOs. See this thread for more details.

2. The Instruction set of the QSPI peripheral is hardcoded in the HW. You need to check the datasheet of your flash device to see that it supports the same instruction set, and verify that it matches the Interface description of the QSPI peripheral. It is possible to define custom instructions, if your device needs special instructions for certain operations. 

3. How to configure and use the QSPI driver is documented on this page.

Best regards,
Jørgen

[xxb9075]

Hi Jørgen,

That's very clear. If the flash I'm using uses a different instruction set, it means I need to build drivers with the nrfx qspi custom instruction API myself right?

Thanks,

Richard