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How to write files in littlefs filesystem SPI External flash ?

parthsanepara

Hi,

I would like to know some techniques or any readily available tools or modules available in the market. to write for ex. .txt, .mp3 files in my external used with my Host MCU via SPI Flash (Winbond). For flash file management I am using littlefs file system. I can able to access the filesystem within MCU access. but I want to write some large files with host PC before mounting flash on the PCB.

Thanks,

Parth

  • Hi,

    There are many ways to skin this. One approach if your PC is a Raspberry Pi (since it has a user-accessible SPI interface) would be to build the littlefs code for the Pi, and let it program the chip. In other words, write an application for the Pi that can write what you need to the Flash.

    Another approach would be to build on a normal PC (desktop or laptop), but transport the SPI commands, from the PC to an external device (e.g. via USB) to translate them back. It may require custom hardware, although there are some USB to SPI devices and ICs out there.

    Yet another approach would be to emulate SPI flash on the PC (you'd need to write that code) using a malloc'd area of memory, so that once the custom littlefs based PC application has written to the emulated flash, then you can dump to a binary file (or other format) and use a standard off-the-shelf USB programmer tool (e.g. 'J-Flash SPI' - I've never tried it) for writing to the external real Flash. There are dozens of similar off-the-shelf products, could even be DIY'd.

    Another approach, that would not require building littlefs on a PC, would be to use a standard programmer to read the SPI flash contents from your working product, and then write it out to as many Flash devices as you require. I've never tried this, so I have no idea if it would work (I don't know littlefs in enough detail to know if it makes use of any unique ID).
    But worth a try since you wouldn't need any custom software, just an off-the-shelf programmer to read and write.

    If that works, there may be existing products (or would be straightforward to build your own custom device) that acts like a standalone storage and programming device (sometimes known as a 'fill gun'). That way, once you've uploaded the Flash contents to it, it is standalone, connect it to your board, and press a single button to program the Flash.

    If your target Flash will not be on a PCB, then you'll also need a socket for the SMD flash (usually known as a SMD ZIF socket). And if you do need to buy that, then it's not worth buying the cheap sliding socket; get the black socket with the large lever, they are (can be) very reliable.

  • Thanks,   

    I found a solution in Zephyr RTOS, which has a module for writing files to external or internal memory with Littlefs or other file systems.