NRF24LE1 how to set PWM frequency?

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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
}
 
 
}
 
}

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One small mistake. The standard servo uses 50Hz PWM signal for control. Here is my new code to generate 50Hz wave using timers. Please correct it.

#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;
P0DIR = 0; // Port1 as output
 
P03 = 0; // Pin 0 of Port 0 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 = 0x43; // initialise timer register lower byte
while(TF0 == 0); // wait for timer overflow flag
TF0 = 0; // clear flag
P03 =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
P03 = 0; // make Pin0 of Port1 low
}

 
 
}

[Håkon Alseth]

Hi,

 

What version of nRF24LE1 are you using?

Pins PWM0 and PWM1 is relative to the QFN package. On the QFN32, PWM0 is P0.2. See chapter 17.3 in the datasheet for more details.

When you are setting "PWMCON = 0xc9; // enable PWM1", you are configuring the base frequency to be 16M/255 * duty_cycle.

If your duty cycle is 50 % (PWMDC0 = 128 in 8 bit mode), it would be (16M/255) * 50% = 31,37 kHz.

If you want 20 kHz output, where you want a base frequency of 40 kHz (* 50 % DC), the closest is:

16M / (31*(x+1)) = 40 kHz, X = (16M / 40 kHz) - 1 = 12.

Try setting PWMDC0 = 16 and PWMCON = 0x33 (bits 5:2 = 12). This should give an approx. output of 19,85 kHz.

If you want to use a TIMER instead, then remember that the base frequency for this one is CLK/12, so 1.333 MHz base frequency for most applications.

 

Kind regards,

Håkon

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I understand in the Khz range but how do I get a 50Hz PWM?

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How do we get a 50Hz PWM wave? What changes should I make to the code.

[infibit]

How do we get a 50Hz PWM wave? What changes should I make to the code.