Difference between revisions of "STM32F107VC/Using MCBQVGA-TS-Display-v12"

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m (Example code)
m (Example code)
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/* Change Display Backlight Intensity
 
/* Change Display Backlight Intensity
  input: 0 - 17 ( 0 = 0% backlight 17 = 100% backlight
+
  input: 0 - 17 ( 0 = 0% backlight (All dark) to 17 = 100% backlight (Brigth)
 
  Cavets: No errorcontrol
 
  Cavets: 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 ) {
 
void backlight( int intensity ) {

Revision as of 07:25, 21 January 2012

Backlight illumination adjust

The signal BL_control[1] turns on the Backlight LED's controlled by the STLD40D[2] 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
/*
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
*/

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 Regisger for channel 3
	TIM3->CCMR2 |= 7 << 4; //PWM mode 1
	TIM3->CCMR2 |= 1 << 3;
	TIM3->EGR |= 1;
	TIM3->CCER |= 1<<8; //Polarity
	TIM3->CCER |= 1<<9;
	// Step  3: Enable Counter 		(TIM3_CR1 bit 0 = 1)
	TIM3->CR1 |= 1;
}

/* Change Display Backlight Intensity
 input: 0 - 17 ( 0 = 0% backlight (All dark) to 17 = 100% backlight (Brigth)
 Cavets: 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

References