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Multiple Flash File Systems

You can create multiple file system instances on the flash memory of the Pico board. This allows you to use different file system types or separate storage areas for different purposes.

Sample Program

In this sample program, we create two LFS::Flash instances and two FAT::Flash instances on the flash memory. Each instance is assigned a unique drive name and a specific region of the flash memory as follows:

Drive Name File System Type Flash Memory Region Size
J: LFS 0x10100000-0x10140000 256kB
K: LFS 0x10140000-0x10180000 256kB
L: FAT 0x10180000-0x101c0000 256kB
M: FAT 0x101c0000-0x10200000 256kB

Build and Flash the Program

Create a new Pico SDK project named fs-flash-multi.

Create Pico SDK Project
  1. In VSCode, run >Raspberry Pi Pico: New Pico Project in the command palette.

  2. In the dialog below, select C/C++. new-project-dialog

  3. Create a project with the following settings:

    • Name ... Enter the project name.
    • Board type ... Select your board type.
    • Location ... Select the parent directory where the project directory will be created.
    • Stdio support ... Leave Console over USB unchecked when you use LABOPlatform or other USB features because they conflict with each other. You can enable it by editing the CMakeLists.txt file later.
    • Code generation options ... Check Generate C++ code.

new-project

Open Existing Pico SDK Project

Open the project folder in VSCode using one of the following methods:

  • In a command prompt, change the current directory to the project folder and execute code ..

  • In a Explorer, choose the project folder, push Alt+D to focus the address bar, and execute code ..

    vscode-from-explorer

If the folder is already prepared as a Pico SDK project, just proceed with editing and building the project.

If not, you will see the following message at the bottom right corner of VSCode.

do-you-want-to-import

Click Yes and you will see the following window.

import-project

Click Import and the project will be prepared as a Pico SDK project.

When the Do you want to import this project as Raspberry Pi Pico project? message disappears before you click Yes, you can reveal it by clicking the icon notify-icon at the bottom right corner of VSCode.

Clone the pico-jxglib repository from GitHub so the direcory structure looks like this:

├── pico-jxglib/
└── fs-flash-multi/
    ├── CMakeLists.txt
    ├── fs-flash-multi.cpp
    └── ...
Clone the Repository

Change the current directory to the parent directory where you want to clone the pico-jxglib repository and run the following commands:

$ git clone https://github.com/ypsitau/pico-jxglib.git
$ cd pico-jxglib
$ git submodule update --init --recursive

pico-jxglib is updated almost daily. If you've already cloned it, run the following command in the pico-jxglib directory to get the latest version:

$ git pull

A directory from a Git repository can safely be moved to another location even after cloning.

Add the following lines to the end of CMakeLists.txt:

CMakeLists.txt
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target_link_libraries(fs-flash-multi
    jxglib_Shell jxglib_Serial jxglib_ShellCmd_Basic
    jxglib_LFS_Flash jxglib_FAT_Flash jxglib_ShellCmd_FS)
add_subdirectory(${CMAKE_CURRENT_LIST_DIR}/../pico-jxglib pico-jxglib)
jxglib_configure_FAT(fs-flash-multi FF_VOLUMES 2)

Enable UART or USB stdio as described below.

Enable UART and/or USB stdio

Find the following lines in CMakeLists.txt:

CMakeLists.txt
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pico_enable_stdio_uart(your-project 0)
pico_enable_stdio_usb(your-project 0)

You can set the value to 1 to enable stdio or 0 to disable it.

  • pico_enable_stdio_uart() enables UART stdio that uses GPIO0 (UART0 TX) and GPIO1 (UART0 RX).
  • pico_enable_stdio_usb() enables USB stdio that uses the USB interface. Make sure to disable USB stdio when you use USB features because they conflict with each other.

Edit fs-flash-multi.cpp as follows:

fs-flash-multi.cpp
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#include <stdio.h>
#include "pico/stdlib.h"
#include "jxglib/Serial.h"
#include "jxglib/Shell.h"
#include "jxglib/LFS/Flash.h"
#include "jxglib/FAT/Flash.h"

using namespace jxglib;

int main()
{
    ::stdio_init_all();
    // Prepare the Shell with Stdio
    Serial::Terminal terminal;
    Shell::AttachTerminal(terminal.Initialize());
    // Declare the flash drive with a name and size (must be a multiple of 4096)
    LFS::Flash driveLFS1("J:", 0x1010'0000, 0x0004'0000);  // 256kB
    LFS::Flash driveLFS2("*K:", 0x1014'0000, 0x0004'0000); // 256kB .. primary drive
    FAT::Flash driveFAT1("L:", 0x1018'0000, 0x0004'0000);  // 256kB
    FAT::Flash driveFAT2("M:", 0x101c'0000, 0x0004'0000);  // 256kB
    for (;;) {
        Tickable::Tick();
    }
}

Build and flash the program to the board.

Build and Flash

The simplest way to build and flash the program is to use the UF2 file generated by the build process. Pico board, a USB cable, and a computer are all you need to get started. Here are the steps to build and flash the program:

  1. Pressing F7 on VSCode will build the project. If this is the first time you build the project, you will see the dialog shown below. Select Pico Using compilers: ... and the build process will start.

    select-a-kit

  2. After building, you can find the generated UF2 file in the build directory.

  3. Connect your Pico to the computer using a USB cable while holding the BOOTSEL button, and it will appear as a mass storage device. Copy the generated UF2 file to this device to flash it. No need to mind the destination directory, just copy it to the root directory of the device.

If you have a debug probe like this, you can also flash the program using OpenOCD and GDB. This is the recommended method for development, as it allows you to debug the program while running it on the board!

Running the Program

Open a terminal emulator to connect the board.

Setup Tera Term for LABOPlatform

Tera Term is available here.

From the menu bar, select [File] - [New Connection...] to open the dialog below:

teraterm-new-connection

pico-jxgLABO or a firmware that links jxglib_LABOPlatform provides two USB serial ports: one for terminal use and the other for applications such as logic analyzers and plotters. Select one of the ports and press Enter key in the terminal. When successfully connected, you will see a prompt in the terminal.

L:/>

A prompt will appear like this:

K:?>

In the prompt, K is the driver name specified by the LFS::Flash instance in the program. The current directory is now ?, indicating the drive is not formatted.

This drive is chosen as the current because it is specified as a primary drive with the drive name prefixed by an asterisk (*) in the constructor.

ls-drive shows the drive information:

K:?>ls-drive -r
 Drive  Format        Total Remarks
 J:     none              0 LFS::Flash 0x10100000-0x10140000 256kB
*K:     none              0 LFS::Flash 0x10140000-0x10180000 256kB
 L:     none              0 FAT::Flash 0x10180000-0x101c0000 256kB
 M:     none              0 FAT::Flash 0x101c0000-0x10200000 256kB

Executing format command with the drive name formats the drive. 

K:?>format J: K: L: M:
drive J: formatted in LittleFS
drive K: formatted in LittleFS
drive L: formatted in FAT12
drive M: formatted in FAT12
K:/>

The prompt changes to /, indicating the drive is now formatted and ready to use. You can create files and directories as usual:

K:/>touch file1 file2 file3
K:/>dir
-a--- 2000-01-01 00:00:00      0 file1
-a--- 2000-01-01 00:00:00      0 file2
-a--- 2000-01-01 00:00:00      0 file3