RP2350 TFT Display with Touch and SD Card Demo

A modular embedded application for RP2350 microcontrollers featuring display, touch, and SD card support with hardware abstraction layers.

Features

• Display Abstraction Layer - Support for multiple display types (ST7796, ST7789, E-Paper)
• Touch Abstraction Layer - Extensible touch controller support (FT6336U)
• SD Card with FatFS - File system support with board-aware initialization
• Multi-Board Support - Automatic pin configuration for different RP2350 boards
• 1-bit Rendering - Memory-efficient monochrome graphics with GUI widgets
• Board Configuration - Single configuration file for all hardware settings

Supported Hardware

Boards

1. Adafruit Feather RP2350 (default)
2. Raspberry Pi Pico 2
3. Raspberry Pi Pico 2 W

Displays

• ST7796 (480x320 TFT LCD) - Fully implemented
• ST7789 - Ready for driver implementation
• E-Paper - Ready for driver implementation

Touch Controllers

• FT6336U (I2C capacitive touch) - Fully implemented
• Extensible for additional controllers

Storage

• SD Card via SPI with FatFS file system

Quick Start

Building for Default Board (Feather RP2350)

mkdir -p build
cd build
cmake -G Ninja ..
ninja

Building for Specific Board

cmake -G Ninja -DPICO_BOARD=pico2 ..
ninja

Available boards: adafruit_feather_rp2350, pico2, pico2_w

Building for All Boards

./build_all_boards.sh

Generates:

• basic1_adafruit_feather_rp2350.uf2
• basic1_pico2.uf2
• basic1_pico2_w.uf2

Flashing

1. Hold BOOTSEL button while connecting USB
2. Copy the .uf2 file to the mounted drive
3. Device will automatically reboot and run

Or use the flash script:

./build_and_flash.sh

Project Structure

basic1/
├── basic1.cpp                      # Main application
├── board_config.h                  # Board-specific pin configuration
├── CMakeLists.txt                  # Build configuration
├── build_all_boards.sh             # Multi-board build script
├── build_and_flash.sh              # Build and flash helper
│
├── display/                        # Display and GUI abstraction
│   ├── low_level_display.h         # Display interface
│   ├── low_level_display_*.cpp     # Display implementations
│   ├── low_level_touch.h           # Touch interface
│   ├── low_level_touch_*.cpp       # Touch implementations
│   ├── low_level_render.h/cpp      # 1-bit rendering engine
│   └── low_level_gui.h/cpp         # GUI widgets
│
├── lib/                            # Hardware drivers
│   ├── ft6336u/                    # FT6336U touch driver
│   ├── st7796/                     # ST7796 display driver
│   ├── sd_card/                    # SD card driver with FatFS test
│   └── fatfs/                      # FatFS filesystem
│
├── fonts/                          # Bitmap font definitions
└── fatfs_time.c                    # FatFS timestamp (uses compile time)

Configuration

Board Configuration (board_config.h)

All hardware settings are defined per board:

// Display configuration
#define DISPLAY_WIDTH 480
#define DISPLAY_HEIGHT 320
#define DISPLAY_TYPE_SELECTED 0  // DISPLAY_TYPE_ST7796

// Touch configuration
#define TOUCH_TYPE_SELECTED 0  // TOUCH_TYPE_FT6336U
#define TOUCH_SWAP_XY true
#define TOUCH_INVERT_X true
#define TOUCH_INVERT_Y false

// SPI pins for display
#define DISPLAY_SPI_PORT spi1
#define DISPLAY_SCK_PIN  18
#define DISPLAY_MOSI_PIN 19
#define DISPLAY_MISO_PIN 20
#define DISPLAY_CS_PIN   17
// ... more pins

Changing Display Type

Modify DISPLAY_TYPE_SELECTED in board_config.h:

• 0 = ST7796 (480x320 TFT)
• 1 = ST7789
• 2 = E-Paper

Changing Touch Type

Modify TOUCH_TYPE_SELECTED in board_config.h:

• 0 = FT6336U
• 1 = None (disable touch)

Touch Coordinate Transformation

Adjust orientation in board_config.h:

#define TOUCH_SWAP_XY true      // Swap X/Y coordinates
#define TOUCH_INVERT_X true     // Invert X axis
#define TOUCH_INVERT_Y false    // Invert Y axis

Architecture

Display Abstraction Layer

Provides a unified interface for different display types:

class LowLevelDisplay {
public:
    virtual bool init() = 0;
    virtual void clear(bool white = true) = 0;
    virtual void draw_buffer(const uint8_t* bit_buffer) = 0;
    virtual void refresh() = 0;
    // ... more methods
    
    static LowLevelDisplay* create(DisplayType type, int width, int height);
};

Usage:

LowLevelDisplay* display = LowLevelDisplay::create(
    (DisplayType)DISPLAY_TYPE_SELECTED, V_WIDTH, V_HEIGHT);
display->init();
display->draw_buffer(buffer);
display->refresh();

Touch Abstraction Layer

Unified interface for touch controllers:

class LowLevelTouch {
public:
    virtual bool init() = 0;
    virtual bool read_touch(TouchData* data) = 0;
    virtual bool is_touched() = 0;
    // ... more methods
    
    static LowLevelTouch* create(TouchType type, int width, int height,
                                 bool swap_xy, bool invert_x, bool invert_y);
};

Usage:

LowLevelTouch* touch = LowLevelTouch::create(
    (TouchType)TOUCH_TYPE_SELECTED, V_WIDTH, V_HEIGHT,
    TOUCH_SWAP_XY, TOUCH_INVERT_X, TOUCH_INVERT_Y);
    
TouchData touch_data;
if (touch->read_touch(&touch_data)) {
    int x = touch_data.points[0].x;
    int y = touch_data.points[0].y;
    // Handle touch
}

SD Card Abstraction

Board-aware initialization:

// Initialize with board configuration
if (sd_card_init_with_board_config()) {
    // Test FatFS functionality
    sd_card_test_fatfs();
}

The test function:

• Mounts FatFS
• Lists directory contents
• Creates and reads test file
• Safely unmounts filesystem

Pin Configurations

Adafruit Feather RP2350

• Display (SPI1): SCK=18, MOSI=19, MISO=20, CS=17, DC=16, RST=15, BL=14
• Touch (I2C0): SDA=4, SCL=5, INT=6, RST=7
• SD Card (SPI1): CS=10 (shares SPI with display)

Raspberry Pi Pico 2 / Pico 2 W

• Display (SPI0): SCK=2, MOSI=3, MISO=4, CS=5, DC=6, RST=7, BL=8
• Touch (I2C0): SDA=12, SCL=13, INT=14, RST=15
• SD Card (SPI1): CS=17

Adding New Hardware

Adding a New Display Driver

1. Create implementation files:

   display/low_level_display_mydriver.h
   display/low_level_display_mydriver.cpp
   

2. Implement the LowLevelDisplay interface

3. Add to factory in low_level_display_factory.cpp:

   case DISPLAY_TYPE_MYDRIVER:
       display = new LowLevelDisplayMyDriver(width, height);
       break;
   

4. Update CMakeLists.txt to include new files

Adding a New Touch Controller

1. Create implementation files:

   display/low_level_touch_mydriver.h
   display/low_level_touch_mydriver.cpp
   

2. Implement the LowLevelTouch interface

3. Add to factory in low_level_touch_factory.cpp

4. Update CMakeLists.txt

Adding a New Board

Edit board_config.h:

#elif defined(PICO_BOARD_MY_CUSTOM_BOARD)
    #define BOARD_NAME "My Custom Board"
    
    // Display configuration
    #define DISPLAY_WIDTH 480
    #define DISPLAY_HEIGHT 320
    #define DISPLAY_TYPE_SELECTED 0
    
    // Touch configuration
    #define TOUCH_TYPE_SELECTED 0
    // ... define all pins
#endif

Memory Usage

• 1-bit framebuffer: 480×320÷8 = 19.2 KB
• Display conversion: Automatic 1-bit → RGB565/monochrome
• Stack/heap: Minimal, uses static buffers where possible

Known Issues & Troubleshooting

Touch Not Working

• I2C Communication Failure: Check wiring, pull-up resistors, I2C address
• Wrong Coordinates: Adjust TOUCH_SWAP_XY, TOUCH_INVERT_X/Y settings

SD Card Not Detected

• CMD0 Returns 0x00: Check card insertion, CS pin, SPI wiring
• Mount Fails: Ensure card is formatted as FAT/FAT32

Display Shows Nothing

• Check SPI wiring and CS/DC/RST pins
• Verify backlight is connected and enabled
• Check voltage levels (3.3V logic)

Features by Component

Display Features

• 1-bit monochrome rendering
• RGB565 color support (ST7796)
• Drawing primitives (lines, rectangles, circles)
• GUI widgets (windows, gauges, status bars)
• Multiple font support

Touch Features

• Multi-touch support (up to 2 points)
• Coordinate transformation
• Touch debouncing
• Event types (press, lift, contact)

SD Card Features

• SPI mode support
• FatFS integration
• Directory listing
• File read/write
• Automatic timestamps from compile time

License

Copyright (c) 2021 Arm Limited and Contributors. All rights reserved. SPDX-License-Identifier: Apache-2.0

Dependencies

• Raspberry Pi Pico SDK 2.2.0+
• FatFS (included)
• TinyUSB (via SDK)
• Hardware drivers (included in lib/)

Contributing

When adding new features:

1. Follow the abstraction layer pattern
2. Update board_config.h for hardware settings
3. Keep application code hardware-agnostic
4. Test on multiple boards if possible
5. Update this README