[SOLVED] Not sure why pulse period not looks the same as code?

[Prakasit Man]

Dear All experts

Now I am using PIC24FJ16GA002 with CCS C compiler (PCWHD). I have written a simple program Blink LED at port B1.
ON/OFF period is 1 ms. But the output that I got on oscilloscope is "3 ms" not as planned at 1 ms both of on and off.

I have connected 30MHz crystal at pin 9(OSCI) and pin 10(OSCO). Both of this pin have a 22 pF ceramic capacitor connected to the ground.

Below is my code. Could you please advise what I am wrong and which statement I should edit? Is it suspecting on FUSES configuration? :-(

#include <24FJ16GA002.h>
#FUSES NOWDT                    //No Watch Dog Timer
#FUSES NOJTAG                   //JTAG disabled
#FUSES NOCKSFSM               //Clock Switching is disabled, fail Safe clock monitor is enabled
#FUSES XT

#device ICSP=1
#use delay(crystal=30MHz)

#define LED PIN_B1
#define DELAY 1

void main()
{
   //Example blinking LED program
   while(true)
   {
      output_low(LED);
      delay_ms(DELAY);
      output_high(LED);
      delay_ms(DELAY);
   }

}

 

[shatruddha]

I had a similar problem once with another controller, I dont know if thats relevent here but in my case it was very stupid. I was using a crystal which was written as 20MHz but actually it was 8MHz. May be you can check for this manufacturing defect by changing crystal

 

[Prakasit Man]

I had a similar problem once with another controller, I dont know if thats relevent here but in my case it was very stupid. I was using a crystal which was written as 20MHz but actually it was 8MHz. May be you can check for this manufacturing defect by changing crystal

Thank you for reply anyway,

I have come back to the datasheet again at the table 27-15.
FUSES has been changed to HS and the fast (HS) oscillator only supports 30MHz over part of it's voltage range.
Anything over 24Mhz, I really need to be using the PLL. So I have changed xtal to 16MHz. It's already work now.

 

[shatruddha]

Oh yeah rite!! dint strike me
Generally such small things go unnoticed. I think I should also make a note of it.
Cheers!!