EXAMPLE.md

Example of pico-vfs library

App	Description
hello	Hello filesystem world.
fs_inits	Examples of file system layout combinations.
multicore_logger	Multi-core logger that saves 1kHz sampling data to an SD card
elastic_mqtt_client	Implements an MQTT client with a local queue to handle network disconnections seamlessly.
usb_logger	Data logger that mounts littlefs and FAT on flash memory and shares it with a PC via USB mass storage class.
benchmark	Data transfer tests with different block devices and different file system combinations.

Building sample code

The pico-sdk build environment is required to build the demonstration, see Getting started with Raspberry Pi Pico to prepare the toolchain for your platform. This project contains a git submodule. When cloning, the --recursive option must be given or a separate git submodule update must be performed.

Firmware can be built from the CMake build directory of pico-vfs.

mkdir build; cd build/
PICO_SDK_PATH=/path/to/pico-sdk cmake ..
make hello fs_init_example multicore_logger usb_logger benchmark

The elastic_mqtt_client uses Wi-Fi, so PICO_BOARD=pico_w needs to be specified. Furthermore, WIFI_SSID, WIFI_PASSWORD, MQTT_USER and MQTT_PASSWORD must be specified in the environment variables when running cmake. This example uses Adafruit IO's MQTT server.

PICO_SDK_PATH=/path/to/pico-sdk WIFI_SSID=SSID WIFI_PASSWORD=PASSWORD MQTT_USER=USER MQTT_PASSWORD=PASSWORD cmake .. -DPICO_BOARD=pico_w
make elastic_mqtt_client

Circuit Diagram

If an SD card is to be used, a separate circuit must be connected via SPI. As an example, the schematic using the Adafruit MicroSD card breakout board+ is as follows

The spi and pin used in the block device argument can be customised. The following pins are used in the demonstration.

Pin	PCB pin	Usage	description
GP18	24	SPI0 SCK	SPI clock
GP19	25	SPI0 TX	SPI Master Out Slave In
GP16	21	SPI0 RX	SPI Master In Slave Out
GP17	22	SPI0 CSn	SPI Chip select