1.75in AMOLED BSP : error in brightness setting command ?

[martinroger]

I tried to use bsp_display_brightness_set on the AMOLED 1.75in screen. The command seems never to return, but does yield.

I perused quickly the CO5300 datasheet for command 0x51, and I am unsure - or I do not understand - the logic in the brightness command :

uint32_t lcd_cmd = 0x51;
    lcd_cmd &= 0xff;
    lcd_cmd <<= 8;
    lcd_cmd |= 0x02 << 24;
    uint8_t param = brightness;
    esp_lcd_panel_io_tx_param(io_handle, lcd_cmd, &param, 1);

Is it really necessary to bitshift it and do an |= 0x02<<24 operation ?

[martinroger]

I tried to use bsp_display_brightness_set on the AMOLED 1.75in screen. The command seems never to return, but does yield.

I perused quickly the CO5300 datasheet for command 0x51, and I am unsure - or I do not understand - the logic in the brightness command :

uint32_t lcd_cmd = 0x51;
    lcd_cmd &= 0xff;
    lcd_cmd <<= 8;
    lcd_cmd |= 0x02 << 24;
    uint8_t param = brightness;
    esp_lcd_panel_io_tx_param(io_handle, lcd_cmd, &param, 1);

Is it really necessary to bitshift it and do an |= 0x02<<24 operation ?

Answering my own question :
Apparently it is necessary to do the bitshifting wizardry and to call a lvgl_port_lock() and lvgl_port_unlock() to get the brightness setting to work.
Setting the brightness without calling for a port lock runs the risk of hanging the command because esp_lcd_panel_io_tx_param would be waiting for a never-ending stream of esp_lcd_panel_io_tx_color() calls to finish.

Wrapping the bsp_display_brightness_set call like this works :

if (lvgl_port_lock(1))
        {
            if (bsp_display_brightness_set(brightness) != ESP_OK)
                ESP_LOGE(__func__, "Cannot set brightness");
            else
                ESP_LOGI(__func__, "Brightness set to %u", brightness);
            lvgl_port_unlock();
        }

Issue can be closed.

[Y1hsiaochunnn]

The backlight function is fine. This AMOLED screen requires writing to the registers within the screen itself. So during the initial setup phase, you can make adjustments, or after the screen initialization is complete, you can make the adjustments through this function.

[martinroger]

Yes, it just didn't occur to me that this could be competing with the other functions that send the actual pixel data, which can be quite busy with LVGL running. Too used to the normal ledc backlights!

Thanks for confirming.

The backlight function is fine. This AMOLED screen requires writing to the registers within the screen itself. So during the initial setup phase, you can make adjustments, or after the screen initialization is complete, you can make the adjustments through this function.