Mbed littlefs mount failure on Seeed Xiao Sense with nrf52840

Electronics and hardware
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1

Hello I’m trying to mount the mbed littlefs to the qspi blockdevice on Seeed Xiao Sense (nrf52840).
I’m using Arduino IDE 2.0.4 on Windows. I installed “seeed nRF52 mbed-enabled Boards” through Arduino board manager. Then I updated the library files according to the commit attached here. So the qspi blockdevice will work on this board.

The qspi blockdevice functionality including read/prog/erase is OK, but when I was trying to mount the littlefs to the qspi blockdevice it failed. The format error code is -4005, which is “Erase command not on sector aligned addresses or exceeds device size” defined on line 32 of QSPIFBlockDevice.h. The mount error code is -138, which I didn’t find the definition. In addition, the qspi blockdevice read size is 4, program size is 4, erase size is 256.
I also tested the littlefs on heap blockdevice, and it worked just fine.
Attached below is my Arduino code. Thanks a lot!

#include “mbed.h”
#include “BlockDevice.h”
#include “QSPIFBlockDevice.h”
#include “LittleFileSystem.h”

#include “HeapBlockDevice.h”

//QSPIFBlockDevice bd(QSPI_FLASH1_IO0, QSPI_FLASH1_IO1, QSPI_FLASH1_IO2, QSPI_FLASH1_IO3, QSPI_FLASH1_SCK, QSPI_FLASH1_CSN, QSPIF_POLARITY_MODE_1, MBED_CONF_QSPIF_QSPI_FREQ);

//mbed::BlockDevice *bd = new mbed::HeapBlockDevice(2048, 1, 1, 512);
//heap blockdevice works fiine

mbed::BlockDevice *bd = new QSPIFBlockDevice(QSPI_FLASH1_IO0, QSPI_FLASH1_IO1, QSPI_FLASH1_IO2, QSPI_FLASH1_IO3, QSPI_FLASH1_SCK, QSPI_FLASH1_CSN, QSPIF_POLARITY_MODE_1, MBED_CONF_QSPIF_QSPI_FREQ);

mbed::LittleFileSystem fs(“fs”);

void setup() {
Serial.begin(115200);
while (!Serial);

Serial.println(“init the blockdevice…”);
int err = bd->init();
if(err) {
Serial.print(“init error. err code=”);
Serial.println(err);
}

Serial.print("bd read size = ");
Serial.println(bd->get_read_size());
Serial.print("bd program size = ");
Serial.println(bd->get_program_size());
Serial.print("bd erase size = ");
Serial.println(bd->get_erase_size());
Serial.print("bd erase value at addr 0 = ");
Serial.println(bd->get_erase_size(0));

int force_format = 1;
if (force_format) {
err = fs.format(bd);
if (err) {
Serial.print("format err = ");
Serial.println(err);
}
}

err = fs.mount(bd);
if (err) {
Serial.print("mount err = ");
Serial.println(err);
}

bd->deinit();
}

void loop() {
Serial.println(“testing done”);
delay(10000);
}

2

Arduino disabled the use of QSPIFBlockDevice. Instead you have to use FlashIAPBlockDevice.
https://os.mbed.com/docs/mbed-os/v6.16/apis/flashiapblockdevice.html

Here’s some code, which may help - this worked on a Raspberry Pi Pico but it has not been tested on a nRF52840.

#include "PluggableUSBMSD.h"
#include "FlashIAPBlockDevice.h"

static FlashIAPBlockDevice bd(XIP_BASE + 0x100000, 0x100000);
USBMSD MassStorage(&bd);

static FILE *f = nullptr;
// Note that file is written to the actual root directory as created when USBMSD is mounted
// File is not stored within a folder called root.
// File is only found when you remove usb and replace again
const char *fname = "/root/myfile.txt";


void USBMSD::begin()
{
  int err = getFileSystem().mount(&bd);
  if (err) {
   //String FN = getFileSystem().getName();
   Serial.println(" filesystem mount failed. Try to reformat device...");
    err = getFileSystem().reformat(&bd);
  }
  if (err) {
    Serial.println("Error: Unable to format/mount the device.");
    while(1);
  }
}


mbed::FATFileSystem &USBMSD::getFileSystem()
{
  static mbed::FATFileSystem fs("root");
  return fs;
}

void writeContents() {
    f = fopen(fname, "w+");
    if (f != nullptr) {
      fprintf(f, "Hello World\n");
      fflush(f);      
      fclose(f);
      Serial.println("Written to File");
    }
    else {
      Serial.println("File not found");
    }  
}

void readContents() {
    f = fopen(fname, "r");
    if (f != nullptr) {
      fclose(f);
      Serial.println("File found");
    }
    else {
      Serial.println("File not found");
    }  
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  MassStorage.begin();
  // If you do not want to wait for Serial Monitor to load then use a long delay here.
  // Found a delay helps if you want to capture the initial serial output.
  while(!Serial) {;;}
  //delay(1000);
  Serial.println("MassStorage mounted");
  Serial.flush();
  //writeContents();
  readContents();

}

void loop() {
  // put your main code here, to run repeatedly:
  
}
3

Thanks for your reply. But I don’t find anything about “Arduino disabled the use of QSPIFBlockDevice”. Actually the qspi chip on Seeed Xiao BLE sense works fine. I just cannot mount a file system on it.
The flashIAP on Xiao BLE sense with nrf52840 writes to the mcu’s internal flash, which is not intended for data storage based on what I read online.

4

Yes, sorry, I realised afterwards that the restriction probably just applies to Raspberry Pico because it uses external flash (uses QSPI too). Code should still work by changing FlashIAPBlockDevice with QSPIFBlockDevice