/*#############################################################################
## Author: Shaun Reed ##
## Legal: All Content (c) 2025 Shaun Reed, all rights reserved ##
## ##
## Contact: shaunrd0@gmail.com | URL: www.shaunreed.com ##
##############################################################################
*/
#ifndef PANEL_DEVICE_H
#define PANEL_DEVICE_H
#include <esp_lcd_panel_dev.h>
#include <esp_lcd_panel_ops.h>
#include <esp_lcd_panel_io.h>
#include <esp_log.h>
#include <display/lv_display.h>
#include "i2c.h"
// LVGL reserves 2x4 bytes in the buffer to be used as a palette.
// This additional space must be added to the IPanelDevice::buf_size_.
#define LVGL_PALETTE_SIZE 8
#define LVGL_TICK_PERIOD_MS 5
#define LVGL_TASK_STACK_SIZE (4 * 1024)
#define LVGL_TASK_PRIORITY 2
#define LCD_H_RES 128
#define LCD_V_RES 64
/**
* Wraps some foundational operations performed on pixel coordinates when
* dealing with pointer arithmetic. Most of these could be done ad-hoc as needed
* but using this helper reduces the risk of errors.
*/
struct Pixel {
/**
* Calculate byte offset for the pixel at [x,y] within a horizontally-mapped
* monochrome uint8 draw buffer, using the initialized horizontal resolution.
*
* We use `>> 3` because each pixel requires 1 bit, but each uint8 in the draw
* buffer can hold 8 bits. To find the uint8 value in our draw buffer that
* stores this pixel's value we must compensate for this when using pixel
* coordinates in byte math.
*
* Therefore, each uint8 in the draw buffer stores the state of 8 pixels.
* Below is an example of calculating for [x, y] pixel coordinates [20, 10].
* The example uses a horizontal resolution of 128.
*
* For the horizontal case, each row (y) of the image is represented by
* `hor_res >> 3` bytes (16). The byte-offset of the first pixel in the 10th
* row for example is `16 * 10` = 160.
*
* Since the pixels are stored horizontally we must calculate the 20th pixel
* column (x) as `160 + (20 >> 3)`, or `160 + (20 / 8)` to get a final offset
* of 162.
*
* @param x X pixel coordinate to find byte offset.
* @param y Y pixel coordinate to find byte offset.
* @param hor_res horizontal resolution of the display.
* @return byte offset for a single-byte monochrome pixel at [x,y].
*/
[[maybe_unused]] [[nodiscard]] static ptrdiff_t
horizontal_byte_offset(const int32_t &x, const int32_t &y,
const int32_t &hor_res = LCD_V_RES)
{
// Convert pixel (bit) coordinates to byte coordinates in the draw buffer.
return (hor_res >> 3) * y + (x >> 3);
}
/**
* Calculate byte offset for the pixel at [x,y] within a vertically-mapped
* monochrome uint8 draw buffer, using the initialized horizontal resolution.
*
* We use `>> 3` because each pixel requires 1 bit, but each uint8 in the draw
* buffer can hold 8 bits. To find the uint8 value in our draw buffer that
* stores this pixel's value we must compensate for this when using pixel
* coordinates in byte math.
*
* Therefore, each uint8 in the draw buffer stores the state of 8 pixels.
* Below is an example of calculating for [x, y] pixel coordinates [20, 10].
* The example uses a horizontal resolution of 128.
*
* For the vertical case, each row (y) of the image is represented by
* `hor_res` bytes (128) - one for each column (x). Because the pixels are
* stored vertically, the byte-offset of the first pixel in the 10th row is
* `128 * (10 >> 3)` or * `128 * (10 / 8)` = 128.
*
* From this location we can simply calculate the 20th pixel column (x) as
* `128 + 20` to get a final offset of 148, because the pixels are stored in a
* columnar format.
*
* @param x X pixel coordinate to find byte offset.
* @param y Y pixel coordinate to find byte offset.
* @param hor_res horizontal resolution of the display.
* @return byte offset for a single-byte monochrome pixel at [x,y].
*/
[[maybe_unused]] [[nodiscard]] static ptrdiff_t
vertical_byte_offset(const int32_t &x, const int32_t &y,
const int32_t &hor_res = LCD_V_RES)
{
// Convert pixel (bit) coordinates to byte coordinates in the draw buffer.
return hor_res * (y >> 3) + x;
}
/**
* Finds the Most Significant Bit location of bit `i` in a byte.
*
* MSB LSB
* bits 7 6 5 4 3 2 1 0
* data 8 7 6 5 4 3 2 1
* Left Right
*
* @return bitmask for MSB location of `i`.
*/
[[maybe_unused]] [[nodiscard]] static uint8_t
msb_mask(const int32_t &i) { return 1 << (7 - i % 8); }
/**
* Finds the Least Significant Bit location of bit `i` in a byte.
*
* LSB MSB
* bits 0 1 2 3 4 5 6 7
* data 1 2 3 4 5 6 7 8
* Left Right
*
* @return bitmask for LSB location of `i`.
*/
[[maybe_unused]] [[nodiscard]] static uint8_t
lsb_mask(const int32_t &i) { return 1 << (i % 8); }
};
/**
* Encapsulates vendor specific ESP LCD panel initialization logic.
* This pure virtual interface can be inherited from for using new LCD devices.
* See SSD1306 as an example to implement IPanelDevice for NT35510 or ST7789.
*
* At this time only I2C is supported.
* Classes that inherit from this interface should likely be marked final.
*/
class IPanelDevice {
public:
/**
* Construct an IPanelDevice.
*
* @param i2c I2C object. Eventually this will mature to IProtocol or similar.
* @param config I2C configuration for this device.
* @param height Height of the device screen in pixels.
* @param width Width of the device screen in pixels.
*/
explicit IPanelDevice(I2C &i2c,
esp_lcd_panel_io_i2c_config_t config,
int width,
int height) :
IPanelDevice(i2c, config, width, height,
width * height / 8 + LVGL_PALETTE_SIZE) { }
/**
* Construct an IPanelDevice.
*
* @param i2c I2C object. Eventually this will mature to IProtocol or similar.
* @param config I2C configuration for this device.
* @param height Height of the device screen in pixels.
* @param width Width of the device screen in pixels.
* @param draw_buf_size Size of the draw buffer for this device.
*/
explicit IPanelDevice(I2C &i2c,
esp_lcd_panel_io_i2c_config_t io_config,
int width,
int height,
size_t draw_buf_size) :
width_(width),
height_(height),
rst_num_(i2c.rst_num_),
lv_buf_size_(draw_buf_size),
esp_io_config_(io_config),
lv_buf_(nullptr) { }
virtual ~IPanelDevice() = default;
//
// PUBLIC METHODS
/**
* Create an LVGL display using the width and height of this device.
*
* @return Handle to the created LVGL display.
*/
[[nodiscard]] lv_display_t *create_display() const
{
auto display = lv_display_create(width_, height_);
assert(display);
return display;
}
/**
* Create an ESP LCD panel IO handle.
*
* @return The created ESP LCD panel IO handle.
*/
[[nodiscard]] esp_lcd_panel_io_handle_t create_io_handle()
{
ESP_LOGI(TAG, "Creating panel IO handle");
esp_lcd_panel_io_handle_t handle = nullptr;
ESP_ERROR_CHECK(
esp_lcd_new_panel_io_i2c(I2C::get(), &esp_io_config_, &handle));
return handle;
}
/**
* Create and initialize an ESP panel handle.
* IPanelDevice implementors must initialize the panel within init_panel.
*
* @param config ESP LCD panel configuration.
* @param io ESP LCD panel IO handle.
* @param [out] panel ESP LCD panel handle output pointer location.
*/
void create_panel(esp_lcd_panel_dev_config_t &config,
esp_lcd_panel_io_handle_t io,
esp_lcd_panel_handle_t &panel)
{
// If the passed handle is already allocated, delete it.
if (panel != nullptr) {
ESP_LOGI(TAG, "Removing unused panel");
esp_lcd_panel_del(panel);
}
ESP_LOGI(TAG, "Installing vendor panel driver");
// Call pure virtual method responsible for initializing the panel handle.
init_panel(config, io, panel);
}
/**
* Retrieve the device specific vendor configuration structure.
*
* @return Address of vendor configuration structure.
* @sa SSD1306::vendor_config
*/
virtual void *vendor_config() = 0;
/**
* Registers LVGL draw buffers and callbacks for this display.
*
* An implementation of the interface can optionally override this method to
* provide custom LVGL callbacks and display configurations.
*
* @param display_handle LVGL display handle to use for rendering.
* @param io_handle IO handle for the ESP LCD panel.
*/
virtual void register_rendering_data(lv_display_t *display_handle,
esp_lcd_panel_io_handle_t io_handle);
/**
* Registers LVGL ticker timer callback for rendering this display.
*
* An implementation of the interface can optionally override this method to
* provide custom LVGL callbacks and tick configurations.
*/
virtual void register_lvgl_tick_timer();
//
// PUBLIC MEMBERS
/// Width of the device screen in pixels.
int32_t width_;
/// Height of the device screen in pixels.
int32_t height_;
/// RST GPIO pin number.
int rst_num_;
/// LVGL draw buffer size for the device.
size_t lv_buf_size_;
/// ESP LCD panel IO configuration.
esp_lcd_panel_io_i2c_config_t esp_io_config_;
protected:
/**
* Static accessor to a static buffer to store draw buffer data for the panel.
*
* This method is protected to allow an implementation to provide a custom
* callback method similar to IPanelDevice::lvgl_flush_cb.
*
* The buffer is allocated statically within the scope of this function to
* allow creating multiple panels that _each_ manage their own statically
* allocated draw buffer data. This simplifies implementing the interface by
* taking this responsibility off of the implementor. The buffer will only be
* allocated if this method is called, so the memory is only used if required.
*
* @return Pointer to uint8 draw buffer data.
* @sa register_rendering_data for overriding LVGL rendering callbacks.
*/
static uint8_t *get_additional_draw_buffer()
{
// Static to the scope of this function, not the compilation unit.
// For LV_COLOR_FORMAT_I1 we need an extra buffer to hold converted data.
static uint8_t oled_buffer[LCD_H_RES * LCD_V_RES / 8];
return oled_buffer;
}
private:
//
// PRIVATE METHODS
/**
* Initializes the ESP panel using vendor specific APIs and configurations.
* This method should implement any setup logic specific to the device.
*
* @param config ESP LCD panel configuration.
* @param io ESP LCD panel IO handle.
* @param [out] panel ESP LCD panel handle output pointer location.
*/
virtual void init_panel(esp_lcd_panel_dev_config_t &config,
esp_lcd_panel_io_handle_t io,
esp_lcd_panel_handle_t &panel) = 0;
//
// PRIVATE STATIC METHODS
/**
* The callback invoked when panel IO finishes transferring color data.
* This signals that the panel is ready to flush image data to the display.
*
* @param panel LCD panel IO handles.
* @param data Panel IO event data, fed by driver.
* @param user_ctx User data, passed from `esp_lcd_panel_io_xxx_config_t`.
* @return Whether a high priority task has been waken up by this function.
* @sa SSD1306::SSD1306 for setting user_ctx data passed to the callback.
* @sa register_rendering_data for overriding this callback.
*/
static bool lvgl_flush_ready_cb(esp_lcd_panel_io_handle_t panel,
esp_lcd_panel_io_event_data_t *data,
void *user_ctx);
/**
* The callback invoked for flushing the rendered image to the display.
*
* `px_map` contains the rendered image as raw pixel map and it should be
* copied to `area` on the display.
*
* The following details are crucial for understanding the logic surrounding
* flushing to the display in this example.
*
* The order of bits within the px_map from _LVGL_ is MSB first.
* MSB LSB
* bits 7 6 5 4 3 2 1 0
* pixels 0 1 2 3 4 5 6 7
* Left Right
*
* The bytes from _LVGL_ are mapped to pixel rows of the display
* 8 bits (pixels) per byte -
* [0, 0, 0, 0, 0, 0, 0, 0]
* [0, 0, 0, 0, 0, 0, 0, 0]
* [0, 0, 0, 0, 0, 0, 0, 0]
*
* The order of bits expected by the _display driver_ is LSB first.
* We must preserve pairing of each bit and pixel when writing to the display.
* LSB MSB
* bits 0 1 2 3 4 5 6 7
* pixels 7 6 5 4 3 2 1 0
* Left Right
*
* Bytes expected by the _display driver_ map to pixel columns of the display.
* 8 bits (pixels) per byte -
* [0, [0, [0, [0,
* 0, 0, 0, 0,
* 0, 0, 0, 0,
* 0, 0, 0, 0,
* 0, 0, 0, 0,
* 0, 0, 0, 0,
* 0, 0, 0, 0,
* 0] 0] 0] 0]
*
* These layouts in memory have no opinion on the shape of the image. The
* beginning and end of a row or a column for example is entirely dependent
* on how the data is accessed. The vertical and horitzontal resolution may
* vary between displays.
*
* For the LV_COLOR_FORMAT_I1 color format we are using, an additional buffer
* is needed for transposing the bits to the vertical arrangement required by
* the display driver that is outlined above.
*
* This callback implementation is an example of handling this transposition
* and flushing the data to the display in the expected format.
*
* @param display LVGL display handle to use for rendering.
* @param area Area of the display being flushed.
* @param px_map Rendered image data for writing to the display area.
* @sa register_rendering_data for overriding this callback.
* @sa get_additional_draw_buffer
*/
static void lvgl_flush_cb(lv_display_t *display,
const lv_area_t *area,
uint8_t *px_map);
/**
* Callback invoked for every period of the timer.
*
* This callback _must_ call lv_tick_inc to inform LVGL how much time has
* elapsed since the last period of the timer.
*
* @param data User data passed to the callback.
* @sa register_lvgl_tick_timer for setting user data and the tick period of
* the timer, or overriding this callback entirely.
*/
static void lvgl_increase_tick_cb(void *data);
/**
* FreeRTOS task callback invoked for handling LVGL events or updating the UI.
*
* This function is intentionally an endless loop and should never return.
* LVGL initialization logic can optionally be added before entering the loop.
* Input logic can optionally be handled within the loop.
*
* This callback _must_ call lv_timer_handler to handle LVGL periodic timers.
*
* @param data User data passed to the callback.
* @sa register_lvgl_tick_timer for overriding this callback.
*/
[[noreturn]] static void lvgl_port_task(void *data);
//
// PRIVATE MEMBERS
/// LVGL draw buffer associated with this Display's lv_display_t.
void *lv_buf_;
/// Tag used for ESP logging.
constexpr static const char *TAG = "IPanelDevice";
};
#endif // PANEL_DEVICE_H