Control Backlight intensity

[arduibag]

Do you have a feature to control the TFT backlight intensity? (with PWM management)

[Adam-Birchall]

Yes, I was looking for this too, check out line 118 of User_Setup.h (and the comments before it):

#define TFT_BL   32            // LED back-light control pin

Then using the PWM controller on the esp you can change the backlight brightness:

ledcSetup(ledChannel, freq, resolution); // 0-15, 5000, 8
ledcAttachPin(TFT_BL, ledChannel); // TFT_BL, 0 - 15
ledcWrite(ledChannel, brightness); // 0-15, 0-255 (with 8 bit resolution)

Check out this PWM on ESP32 tutorial for more info

[arduibag]

Thanks a lot! For the frequency, it says "For an LED, a frequency of 5000 Hz is fine to use." but how is it calculated? Do you know?

[rin67630]

Hi @AReubens,

Why do you recommend to check out line 118 of User_Setup.h? TFT_BL is defined elsewhere it works without that.

[rin67630]

Due to the specificity of the ESP32 to have 16 assignable PWM controller channel, the user must define a channel to use. The library should not use a channel on its own.

[capedra]

On the file "Setup25_TTGO_T_Display.h", we can see that TFT_BL pin uses GPIO4. So, on User_Setup_Select.h file, we uncomment the following line: #include <User_Setups/Setup25_TTGO_T_Display.h> // Setup file for ESP32 and TTGO T-Display ST7789V SPI bus TFT And after that, it's just a matter of controlling the brightness, which basically is:

pinMode(TFT_BL, OUTPUT);
ledcSetup(0, 5000, 8); // 0-15, 5000, 8
ledcAttachPin(TFT_BL, 0); // TFT_BL, 0 - 15
ledcWrite(0, 1); // 0-15, 0-255 (with 8 bit resolution); 0=totally dark;255=totally shiny

Well, an alternative method:

void setBrightness(uint32_t newBrightness) {
  ledcWrite(0, newBrightness); // 0-15, 0-255 (with 8 bit resolution);  0=totally dark;255=totally shiny
}
void configPins() {
  pinMode(TFT_BL, OUTPUT);
  ledcSetup(0, 5000, 8); // 0-15, 5000, 8
  ledcAttachPin(TFT_BL, 0); // TFT_BL, 0 - 15
}
void setup() {
  configPins();
  setBrightness(1); // 0=OFF;255=MAX. BRIGHTNESS
}

[rin67630]

For the frequency, it says "For an LED, a frequency of 5000 Hz is fine to use." but how is it calculated? Do you know? Everything above 100Hz is fine.

[nOfOKUz]

Hi, Thanks for that tricks, that was what I was looking for. Thought I am not seing any intensity changes on my TTGO screen going from 0 to 255. Is there something I missed? Is it working for you. TT

[hasaranga]

same here...

[hasaranga]

Found the issue. you need to set brightness after tft.init() function call.

pinMode(4, OUTPUT); analogWrite(4, brightnessLevel);