PIC12F683 UART_Soft problems

[imranahmed]

T2CON = 0x04; // prescaler + turn on TMR2;
PR2 = 0x31; // freq 0x31 for 40kHz
CCPR1L = 0x17; // set low time 0x17 for 40kHz
CCP1CON = 0x30; // duty lowest bits + PWM mode (PWM off)

If i want to set frequency 56kHz so what will be change in above values and where i find CCPR1L register in
datasheet?

 

[bigdogguru]

You haven't stated the oscillator frequency (Fosc) of the PIC12F683, however from the values you have supplied above the Fosc appears to be 8MHz.

Reference: PIC12F683 Datasheet, Section: 11.3.1 PWM PERIOD, Page: 79

PWM Period = [(PR2) + 1] • 4 • TOSC • (TMR2 Prescale Value)

Note: TOSC = 1/FOSC

Rearrange:

PR2 = Fosc/(Fpwm * 4 *(TMR2 Prescale Value) ) - 1

Pulse Width Modulation (PWM) Calculations for PIC Micros


Not all PWM frequencies (Fpwm) are viable for a given device oscillator frequency (Fosc).

The closest obtainable PWM frequency to the desired 56kHz for the given 8MHz maybe 55.5556kHz.

Which requires a PR2 = 35/0x23 for TMR2 prescaler of 1 and 50% duty cycle CCPR1L = 17/0x11, CCP1CON = 60/0x3C

Or requires a PR2 = 8/0x08 for TMR2 prescaler of 4 and 50% duty cycle CCPR1L = 4, CCP1CON = 28/0x1C

/*
 * PWM registers configuration
 * Fosc = 8000000 Hz
 * Fpwm = 55555.56 Hz (Requested : 56000 Hz)
 * Duty Cycle = 50 %
 * Resolution is 7 bits
 * Prescaler is 4
 * Ensure that your PWM pin is configured as digital output
 * see more details on http://www.micro-examples.com/
 * this source code is provided 'as is',
 * use it at your own risks
 */
PR2 = 0b00001000 ;
T2CON = 0b00000101 ;
CCPR1L = 0b00000100 ;
CCP1CON = 0b00011100 ;

You can also use the following calculator for PWM module values:

PIC PWM Calculator & Code Generator



The CCPR1L register is discussed throughout Section 11.0 CAPTURE/COMPARE/PWM(CCP) MODULE, beginning on Page 75.

Is there something in particular you wish to know concerning the CCPR1L Register?



BigDog

 

[imranahmed]

Please let me know what is problem in my attached ADC_PWM code it is not working properly.