STM32F107VC/Using MCBQVGA-TS-Display-v12

Backlight illumination adjust

The signal BL_control turns on the Backlight LED's controlled by the STLD40D IC on the display. To control the illuminace of the LED's its necessary to turn the LED's off and on using Pulse-Width-Modulation (PWM).

Keil MCBSTM32C board

On the Keil MCBSTM32C board the BL_control signal is connected to PB0 (Port B bit 0).

1. Looking in the Reference Maual on page 173 section 9.3.7 table 44 it's seen that Timer 3 Channel 3 has an alternate function on PB0.
2. To see Timer 3's possibilities on PB0 look on page 161 section 9.1.11 table 23 it's seen that timer 3 can use a GPIO pin as Output Compare Channel X when the pin is configured as Alternate Function Push-Pull.
3. To set PB0 as Alternate Function Push-Pull - See the GPIOx_CRL register on page 166.
4. To configure Timer 3 as continues PWM output timer see Page 371 section 15.3.9

Example code

Still experimental and missing documentation

Note

To change Pulse Width change the value of TIM3->CCR3

#include "GPIO_STM32F10x.h"
/*
Example 2:
==========
Using timer 3 to Dim the Backlight in Display

Mode : Continues PWM mode to PB0. Section 15.3.9 page 370
    For details see: http://mars.tekkom.dk/mediawiki/index.php/STM32F107VC/Using_MCBQVGA-TS-Display-v12

Caveats: Assumes TIMxCLK = 72 MHz (See RCC - Reset And Clock Control)
*/

void tim3init( void ) {
	GPIOB->CRL |= 0xa;  // Set PB0 as Alternate function Push-Pull 
	RCC->APB1ENR |= 2; //Enable timer 3 clock 	(RCC->APB1ENR bit 1 = 1)
		
    
	TIM3->PSC = 72;	  // Prescaler: With timer 3 input clock 72 Mhz divide by 72 to 1 Mhz
	TIM3->ARR = 1000; // Auto Reload Register set to 1000 divide 1Mhz/1000 = 1 Khz
	TIM3->CCR3 = 100; //Compare Register for channel 3
	TIM3->CCMR2 |= 7 << 4; //PWM mode 1
	TIM3->CCMR2 |= 1 << 3;
	TIM3->EGR |= 1; //Update generate
	TIM3->CCER |= 1<<8; //Polarity
	TIM3->CCER |= 1<<9;
	TIM3->CR1 |= 1;
}

/* Change Display Backlight Intensity
 input: 0 - 17 ( 0 = 0% backlight (All dark) to 17 = 100% backlight (Brigth)
 Caveats: No errorcontrol
             When 0 the timer should be turned off and the backlight turned off (PB0=0)
             when 17 the timer should be turned off and the backlight turned on (PB0=1)
*/
void backlight( int intensity ) {
	int disvalarr[] = {0,5,10,15,25,35,50,65,80,100,120,150,200,300,400,600,800,1000};
	TIM3->CCR3 = disvalarr[intensity];
}

Links

• MCBSTM32C Display Schematics (Loads PDF)
• AM-240320LDTNQW TFT-LCD Display module with Touch Panel (Loads PDF)
  • Display modules??
• SPFD5408B 720 channel driver for TFT-LCD Display (Loads PDF)
• STMPE811 Touch Screen Controller
• STLD40D White LED power supply for large display backlight (Loads PDF)