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Grove LCD backlight module library – Raspberry Pico SDK port

This is a library for driving the Grove LCD backlight, ported from the Arduino library provided by Seeed Studio. The library works by same logic, but is re-written to use Pico SDK's i2c library instead of Wire.h, and using C instead of C++.

The original library can be found in Seeed Studio github. All additions are provided under the original license.

An example pico program is provided in grove-lcd-pico-example repository.

Usage

The port can be easily integrated into a Pico SDK project as a git submodule.

git submodule add https://github.com/sampsapenna/grove-lcd-pico.git
git submodule update

After cloning the repository you need to add the library to CMakeLists.txt used when building the project. Add the following lines before target_link_libraries:

add_subdirectory("grove-lcd-pico")

target_include_directories(rgb_lcd PUBLIC "grove-lcd-pico")
target_link_directories(rgb_lcd PUBLIC "grove-lcd-pico")

Additionally you will need to add the required libraries to linking, by adding hardware_i2c rgb_lcd pico_binary_info to target_link_libraries.

Libary does not initialize i2c, but assumes that program initializes i2c for it. Default initialization, sourced from Raspberry Pi Pico documentation, can look e.g. like this:

    i2c_init(i2c_default, 100 * 1000);
    gpio_set_function(PICO_DEFAULT_I2C_SDA_PIN, GPIO_FUNC_I2C);
    gpio_set_function(PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C);
    gpio_pull_up(PICO_DEFAULT_I2C_SDA_PIN);
    gpio_pull_up(PICO_DEFAULT_I2C_SCL_PIN);
    // Make the I2C pins available to picotool
    bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C));

Header file to include is rgb_lcd.h, same as in the Arduino library.

Library defaults to using i2c0_inst, which is fine for most purposes. Some shields only expose i2c0_inst, so this parameter is made configurable via GROVE_PICO_SHIELD flag on compile-time.

Some functions, especially the high level ones, use sleep_ms function for timing. As such, these funcions should only be used outside time-critical code, e.g. in a setup() function, since they can mess up the timing of other unrelated code in the program. For implementation details, inspect rgb_lcd.c for which funcions use sleep_ms for timing.

Bugs

The library has been tested with the grove blue/white display, but not the RGB library. This means there might be bugs. Additionally, the drawing logic could be improved, lcd_write() function currently drawing a single character at a time.

If you encounter a bug, go ahead and open an issue.