Hi there,
Description
I want to porting to STM32 Discovery F746NG runned on MBedOS5 but I had only black screen and after 10hours I have no idea where to continue. I am sure i misunderstood something.
What MCU/Processor/Board and compiler are you using?
Discovery F746NG
What do you want to achieve?
I want to use the LittlevGL together with the Mbed on the ST boards but for a start I want to see a simple label or a button. Later I want to share on Mbed web because sometimes users ask about a GUI library. I found few discussions where someone tried to do that but still not finished and after 6 months no updates.
What have you tried so far?
Because the ST published drivers for that board on the Mbed I have tested the touchscreen and I know is working.
I tried to follow instructions from this web or from the github but without successful = black screen. Only touch working well.
However I had a problem because compiler show me an error and then I found a different struct type as argument in the my_disp_flush example from Quick overview page.
The flush_cb of the struct _disp_drv_t wants as parametr a pointer to the _disp_drv_t type
void (*flush_cb)(struct _disp_drv_t * disp_drv, const lv_area_t * area, lv_color_t * color_p);
But the my_disp_flush function have a pointer to the lv_disp_t type as parametr.
void my_disp_flush(lv_disp_t * disp, const lv_area_t * area, lv_color_t * color_p)
{
/*rest of code*/
lv_disp_flush_ready(disp); /* Indicate you are ready with the flushing*/
}
I need to know what is correct because I replace it with struct _disp_drv_t and that of course solve my problem with the compiler’s error but I have black screen 
If you were kind and send me to the correct direction, I would be very grateful.
Code to reproduce
#include "mbed.h"
#include "TS_DISCO_F746NG.h"
#include "LCD_DISCO_F746NG.h"
#include "lvgl/lvgl.h"
#include "lv_conf.h"
#include "demo.h"
#define TICK_DEF 10
#define TICKER_TIME 0.001 * TICK_DEF
Ticker ticker; /*Initialize your system tick*/
LCD_DISCO_F746NG lcd; /*Initialize your display driver*/
TS_DISCO_F746NG ts; /*Initialize your touchpad driver*/
TS_StateTypeDef TS_State; /*Initialize your touch state sctruct*/
void lv_ticker_func();
void my_disp_flush(lv_disp_drv_t* disp_drv, const lv_area_t* area, lv_color_t* color_p);
bool my_touchpad_read(lv_indev_drv_t * indev_driver, lv_indev_data_t * data);
static void event_handler(lv_obj_t * obj, lv_event_t event);
int main()
{
printf("Example of MbedOS5 with LittlevGL on Disco F746NI \n");
//lcd.DisplayStringAt(0, LINE(5), (uint8_t *)"LittlevGL DEMO", CENTER_MODE);
ticker.attach(&lv_ticker_func,TICKER_TIME);
wait(0.5);
lv_init(); /*Initialize the LittlevGL*/
static lv_disp_buf_t disp_buf;
static lv_color_t buf[LV_HOR_RES_MAX * 10]**strong text**; /*Declare a buffer for 10 lines*/
lv_disp_buf_init(&disp_buf, buf, NULL, LV_HOR_RES_MAX * 10); /*Initialize the display buffer*/
/*Implement and register a function which can copy a pixel array to an area of your display*/
lv_disp_drv_t disp_drv; /*Descriptor of a display driver*/
lv_disp_drv_init(&disp_drv); /*Basic initialization*/
disp_drv.flush_cb = my_disp_flush; /*Set your driver function*/
disp_drv.buffer = &disp_buf; /*Assign the buffer to the display*/
lv_disp_drv_register(&disp_drv); /*Finally register the driver*/
/*Implement and register a function which can read an input device. E.g. for a touch pad*/
ts.Init(lcd.GetXSize(), lcd.GetYSize()); /*ST touch initialization*/
lv_indev_drv_t indev_drv; /*Descriptor of a input device driver*/
lv_indev_drv_init(&indev_drv); /*Basic initialization*/
indev_drv.type = LV_INDEV_TYPE_POINTER; /*Touch pad is a pointer-like device*/
indev_drv.read_cb = my_touchpad_read; /*Set your driver function*/
lv_indev_drv_register(&indev_drv); /*Finally register the driver*/
demo_create();
while(1) {
lv_task_handler(); /*Call lv_task_handler() periodically every few milliseconds. It will redraw the screen if required, handle input devices etc.*/
wait_ms(10);
}
}
void lv_ticker_func(){
lv_tick_inc(TICK_DEF); /*Call lv_tick_inc(x) every x milliseconds in a Timer or Task (x should be between 1 and 10). It is required for the internal timing of LittlevGL.*/
}
void my_disp_flush(lv_disp_drv_t* disp_drv, const lv_area_t* area, lv_color_t* color_p)
{
/*The most simple case (but also the slowest) to put all pixels to the screen one-by-one*/
uint16_t x, y;
for(y = area->y1; y <= area->y2; y++) {
for(x = area->x1; x <= area->x2; x++) {
//put_px(x, y, *color_p)
lcd.DrawPixel( x, y, color_p->full);
//color_p++;
}
}
/* IMPORTANT!!!
* Inform the graphics library that you are ready with the flushing*/
lv_disp_flush_ready(disp_drv);
}
bool my_touchpad_read(lv_indev_drv_t * indev_driver, lv_indev_data_t * data)
{
static lv_coord_t last_x = 0;
static lv_coord_t last_y = 0;
/*Save the state and save the pressed coordinate*/
ts.GetState(&TS_State);
if(TS_State.touchDetected == 0){
data->state = LV_INDEV_STATE_PR;
}else{
data->state = LV_INDEV_STATE_REL;
}
//data->state = tttt ? LV_INDEV_STATE_PR : LV_INDEV_STATE_REL;
if(data->state == LV_INDEV_STATE_PR){
//touchpad_get_xy(&last_x, &last_y);
last_x = TS_State.touchX[0];
last_y = TS_State.touchY[0];
}
/*Set the coordinates (if released use the last pressed coordinates)*/
data->point.x = last_x;
data->point.y = last_y;
return false; /*Return `false` because we are not buffering and no more data to read*/
}
static void event_handler(lv_obj_t * obj, lv_event_t event)
{
if(event == LV_EVENT_CLICKED) {
printf("Clicked\n");
}
else if(event == LV_EVENT_VALUE_CHANGED) {
printf("Toggled\n");
}
}
Thank you
BR, Jan