docs: alternative build options required for `port/rp2`

r00t1900 commented 2 years ago

description

Currently I bought an official raspberry pi pico board and a third-party pico board. One of the difference between them is the size of flash: the third-party board use an 4MB Flash instead of 2MB Flash in pi pico.

However, after I download the precompiled .u2f firmware file for pi pico and flash it to both of them, I got the same available space of filesystem:

os.statvfs('/')

Both of them output is about 1.38MB in total(calculated by blocks*bsize), as the firmware has already took about 500-600KB size for storage so the total flash size should be 2MB.

some thoughts

I guess that may be something define in the make steps. I lookup in port/rp2 and found a marco in rp2_flash.c:

#ifndef MICROPY_HW_FLASH_STORAGE_BYTES
#define MICROPY_HW_FLASH_STORAGE_BYTES (1408*1024)
#endif

And 1408KB is exactly almost equal to 1.37MB. Is this the main reason why either W25Q16 or W25Q32 perform the same available filesystem size? I've also notice that the include part of rp2_flash.c:

...
#include "hardware/flash.h`
...

But I can not find the corresponding file hardware/flash.h.

questions

how to reconfigure for other flash size What should I do if I would like to build an alternative micropython firmware for a pico-like board? Maybe different in flash,crystal and pin layout. Where should I reconfigure before building?(mainly is the flash size)
how to operate more flash components The official pi pico is designed with flash connected to XIP via a single QSPI interface. But what should I do if I want to operate one more flash via the normal/common spi interface?(the speed is not a problem). I would like to storage data into different flash components, like 8 flash chips and switch them by CS signal. Can they be use as an another standalone filesystem with littlefs? If no, is there any spi-flash api for micropython to read/write/erase external flash component? If no, then I have to implement all basic spi-flash functions.

Thanks for reading and looking forward to your replies :)

In this case we can assume that the flash is W25QXX for getting started, while XX is range from 16 to 128.

peterhinch commented 2 years ago

This support query should be raised in the forum rather than in this bug tracker.

Re using a set of SPI flash chips to create a filesystem see this repo.

r00t1900 commented 2 years ago

This support query should be raised in the forum rather than in this bug tracker.

Re using a set of SPI flash chips to create a filesystem see this repo.

I found some interesting posts on the forum and some marco I found useful is PICO_FLASH_SIZE_BYTES and MICROPY_HW_FLASH_STORAGE_BYTES. Is that correct? I would like to try it and find out myself. you are so brilliant! I've also found your replies on the micropython forum! Posts are:
Rpeo micropython_eeprom is very good! that's what I am pointing for. What's the different bewtween rp2.Flash and this spi_flash.Flash? Is the former can only operate internal flash mounted on QSPI and the latter can operate most of the external flash wired on SPI bus?

micropython / micropython