How to use usb_msh example with custom external flash memory chip?

[Kristopher]

Hi,

I would like adjust usb_msc to work with flash memory different than in example. I created nrf_serial_flash_params_t structure with it's data. When I trying to change  erase_size field to 

262144 (my flash has 256-kbyte erase sectors) I get NRF_ERROR_NOT_SUPPORTED inside disk_initialize function. 

I tried solve the problem by increasing NRF_BLOCK_DEV_QSPI_ERASE_UNIT_SIZE const in nrf_block_dev_qspi.h, but it resoults  region `RAM' overflowed by 6988 bytes error.

I Used nRF52840 with SDK14.0

Is it possible to adjust this example with such external flash chip?

[haakonsh]

Hey Kristopher,

I'm afraid I will not be able to help you until after the Easter holidays. 

FYI: SDK15 is scheduled for release on monday, you should check out the QSPI example as see if there's anything interesting there. 

Cheers,

Håkon.

[Kristopher]

hey, I downloaded sdk 15 saw QSPI related examples and tried to run my app with new sdk, but i still obtain same error. Is is possible at all to adjust this example (It's repleted with many pieces of code in whole sdk i think)?

[haakonsh]

Hey Kristopher, sorry for the long delay.

Do you mind sharing code so that I can reproduce your issue? 

Do you mind sharing the datasheet for the memory device?

Cheers,

Håkon.

[haakonsh]

I've reproduced your issue. The nrf_block_dev_qspi library creates a buffer the size of an flash page, that is used when erasing parts of a page. When you only want to erase a part, the whole page gets loaded in to RAM, followed by a page erase, and a re-flashing of the page with the content stored in the RAM buffer. At 256KB page size, you will have filled the entire RAM with only this buffer. You will need to re-write some of the QSPI implementation of the Block device library so that you do not use a RAM buffer.