Generating PWM of 6.5khz on pin 1.1 with duty cycle 50% on CC2541

According to CC254x user guide, Timer 3 cannot output PWM to P1.1. You can check Table 7.1 Peripheral I/O Pin Mapping in CC254x user guide.

Hi,

I've Changed the timer to timer 4 with alt location 1.

This is the modified code. How can I change the duty cycle in this ?

PERCFG &= ~BV(4)             // Timer 4 Alternate location 1
P1SEL |= BV(1);             // Peripheral function on P1_1   //P1SEL |= BV(1);
P1DIR |= BV(1);             // P1_1 = output  
    
T4CTL &= ~0x10;             // Stop timer 4 (if it was running)
T4CTL |= 0x04;              // Clear timer 4
T4CTL &= ~0x08;             // Disable Timer 4 overflow interrupts
T4CTL |= 0x03;              // Timer 4 mode = 3 - Up/Down

T4CCTL0 &= ~0x40;           // Disable channel 0 interrupts
T4CCTL0 |= 0x04;            // Ch0 mode = compare
T4CCTL0 |= 0x10;            // Ch0 output compare mode = toggle on compare

uint8 prescaler = 0;
uint8 frequency= 6500;

// Get current Timer tick divisor setting
uint8 tickSpdDiv = (CLKCONSTA & 0x38)>>3;

// Calculate nr of ticks required to achieve target frequency
uint32 ticks = (8000000/frequency) >> tickSpdDiv;      // 8000000 = 32M / 4;

// Fit this into an 8bit counter using the timer prescaler
while ((ticks & 0xFFFFFF00) != 0)
{
    ticks >>= 1;
    prescaler += 32;
}

// Update registers
T4CTL &= ~0xE0;
T4CTL |= prescaler;
T4CC0 = (uint8)ticks;

// Start timer
T4CTL |= 0x10;

I'm trying to generate PWM of 6.5 khz on pin P1_1 with duty cycle 50%. I'm using Timer 1 alt location 2 but it doesn't seem to work.

It's looking really complicated for me. Can someone please share the code ?

Thanks 

Hi,
I'm trying to generate a PWM output on P1.1 of frequency 6.5khz and 50% duty cycle. 

I'm using Timer1 alt location 2. I'm not sure how to set frequency and duty cycle. Here the code snippet:

PERCFG |= BV(6); // Timer 1 Alt 2 for Pin 1.1
P1SEL |= BV(1);  // Set P1.1 to peripheral 
P1DIR |= BV(1);  // Set P1.1 to output
    
T1CNTL = 0x00;  // Reset Counters
T1CNTH = 0x00;
    
T1CTL = 0x00;  //Control Reset
T1CTL |= (0x3<<2); // Tick Freq /128
    
T1CCTL1 = 0x00; // Channel Capture Control Reset
T1CCTL1 |= BV(2); //Compare Mode
T1CCTL1 |= (0x2<<3);  // Toggle on Compare
    
T1CC1L = 0xFF;  //Duty Cycle 50%
T1CC1H = 0x00;
    
T1CTL |=(1<<1);  // Start Timer

Can anyone please tell me how to make it work.

Hi Sanat, 

Please note this from section 7.6.1 of the User Guide:

P2SEL.PRI1P1 and P2SEL.PRI0P1 select the order of precedence when assigning several peripherals
to Port 1. The Timer 1 channels have precedence when the former is set low and the latter is set high.

For 6.5 kHz operation, You should set the timer period to 32000/6.5= 4923 and to get the duty cycle on P1.1 to be 50%, you should set ch1 compare value to 4923/2=2462. 

Peder