NRF24LE1 how to set PWM frequency?

[infibit]

To what values should I set the PWMCON register to so that the PWM0 and PWM1 frequency is output at 20Khz with duty cycle varying between 1 to 2ms. Now specifically I am asking this after reading the data sheet because the tables mentioned are not clearing giving information. How do I decipher the table given here:

Please clearly disclose information in the data sheets. Also give an example to show how to set to particular frequency and pulse width.

Let me tell you how I decipher this as a newbie. Now CCLK is 16,000,000 for 16Mhz clock. I chose PWM0 as output so bit 0 is 1 and bit 1 is 0. Now I need to find out what PWMCON is so the formula for PWMCON for 20Khz PWM freq will be. (16000000/(255 x 20000))-1 = 160/51 -1 which is approximately 2. Hence PWMCON[5:2] will be 0010. There fore PWMCON will be 11001001 which is 0xC9. But this dint work when I put in this value for PWMCON as the servo did not rotate. Here is my code.

#include "reg24le1.h" // I/O header file for NRF24LE1
#include "hal_delay.h" // header file containing delay functions
 
// main function
void main()
{
int i = 0, j = 0; // loop variable
P0DIR = 0; // Port 0 as output
PWMCON = 0xc9; // enable PWM1
 
// infinte loop
while(1)
{
for(i= 180; i--; i > 0)
{
PWMDC0 = i ; // change duty cycle
delay_ms(10); // delay of 10 ms
}
 
 
}
 
}

[Håkon Alseth]

It does not go that far down. From the documentation:

The following table shows how the PWM frequency (or period length) and the PWM duty cycle are controlled
by the PWM SFR registers. PWM frequency range is approximately 4 kHz-254 kHz.

[infibit]

Is there a way that I can generate a way by software methods using timers. Generally in arduino they have a software library based PWM. They use timers. How can use timers to generate a 50Hz PWM?

[Håkon Alseth]

We do not have a softPWM library available for the nRF24L-series devices. You'll have to manually use the timer to generate the pulse.

 

Kind regards,

Håkon

[infibit]

Here is a 15ms timer delay pulse. How do I change it to get a 20ms delay pulse and thus a 50Hz pulse?

#include "reg24le1.h" // I/O header file for NRF24LE1
#include <stdlib.h> // standard library
#include <string.h> // library containing string functions
#include <stdio.h> // standard I/O library
 
sfr16 DPTR = 0X82; // declare functional register DPTR
 
// main function
void main()
{
 
int i = 0;
P1DIR = 0; // Port1 as output
 
P10 = 0; // Pin 0 of Port 1 low
 
EA = 1; // Enable global interrupt
TMOD = 0X01 ; // timer0 in 16bit mode1
TR0 = 1; // start timer
 
// infinite loop
while(1)
{
TH0 = 0; // initialise timer register upper byte
TL0 = 0; // initialise timer register lower byte
while(TF0 == 0); // wait for timer overflow flag
TF0 = 0; // clear flag
P10 =1; // make Pin0 of Port1 high
TH0 = 0; // initialise timer register upper byte
TL0 = 0; // initialise timer register lower byte
while(TF0 == 0); // wait for timer overflow flag
TF0 = 0; // clear flag
P10 = 0; // make Pin0 of Port1 low
}
}

 

[Håkon Alseth]

Could you try this instead?

#include <stdio.h>
#include <stdint.h>
#include "nrf24le1.h"

void timer0_init(void)
{
  TMOD |= 0x01; //16 bit timer
  TR0 = 1; //start timer
  ET0=1; //enable interrupt

}


void t0_interrupt(void) interrupt 1
{       
  // Timer increments every 2*12 CPU clock cycles    
  // Timer starts counting down from 65535
  // 6666 * 1,5 us = 9999 us
  uint16_t timer_val = 0xFFFF - 6666;
  P10 ^= 1;
  TL0 = (uint8_t) (timer_val & 0xFF);
  TH0 = (uint8_t) ((timer_val >> 8) & 0xFF);
}

void main(void)
{
    // Configure TXD pin as output.
    // P0.5, P0.3 and P1.0 are configured as outputs to make the example run on
    // either 24-pin, 32-pin or 48-pin nRF24LE1 variants.
    P0DIR = 0x00;
    P1DIR = 0x00;  

    CLKCTRL |=  0x1;
    // Enable global interrupts
    EA = 1;
    timer0_init();
    for(;;)
    {    
     
    }
}

This should generate a 50 hz pulse.

Kind regards,

Håkon