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PIC12LF1822 and PIC16LF1823 clock problems

 
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janbbeck



Joined: 23 Dec 2010
Posts: 7

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PIC12LF1822 and PIC16LF1823 clock problems
PostPosted: Thu Dec 23, 2010 10:59 am     Reply with quote

I cannot figure out how to get the delay_ms function to work. I can get delays by using the delay_cycles only.

The long version:
I am using the 12lf1822 and make a sample program using the pic wizard. I am simply trying to blink an LED.

first, the .h file produces a mess with the fuses:
Code:

#include <12LF1822.h>

#FUSES NOWDT                    //No Watch Dog Timer
#FUSES INTRC_IO                 //Internal RC Osc, no CLKOUT
#FUSES WDT_SW                #FUSES NOPUT                    //No Power Up Timer
#FUSES MCLR                     //Master Clear pin enabled
#FUSES NOPROTECT                //Code not protected from reading
#FUSES NOCPD                    //No EE protection
#FUSES NOBROWNOUT               //No brownout reset
#FUSES NOCLKOUT              #FUSES NOIESO                   //Internal External Switch Over mode disabled
#FUSES NOFCMEN                  //Fail-safe clock monitor disabled
#FUSES NOWRT                    //Program memory not write protected
#FUSES PLL                   #FUSES NOSTVREN                 //Stack full/underflow will not cause reset
#FUSES BORV19                #FUSES NODEBUG                  //No Debug mode for ICD
#FUSES NOLVP                    //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O

#use delay(int=4000000)
#define LED PIN_A5
#define DELAY 1000


which I fixed like this:
Code:

#include <12LF1822.h>

#FUSES NOWDT                    //No Watch Dog Timer
#FUSES INTRC_IO                 //Internal RC Osc, no CLKOUT
#FUSES WDT_SW               
#FUSES NOPUT                    //No Power Up Timer
#FUSES MCLR                     //Master Clear pin enabled
#FUSES NOPROTECT                //Code not protected from reading
#FUSES NOCPD                    //No EE protection
#FUSES NOBROWNOUT               //No brownout reset
#FUSES NOCLKOUT             
#FUSES NOIESO                   //Internal External Switch Over mode disabled
#FUSES NOFCMEN                  //Fail-safe clock monitor disabled
#FUSES NOWRT                    //Program memory not write protected
#FUSES PLL                   
#FUSES NOSTVREN                 //Stack full/underflow will not cause reset
#FUSES BORV19               
#FUSES NODEBUG                  //No Debug mode for ICD
#FUSES NOLVP                    //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O

#use delay(int=4000000)
#define LED PIN_A5
#define DELAY 1000


the main program reads:
Code:

void main()
{
    //setup_comparator(NC_NC_NC_NC);// This device COMP currently not supported by the PICWizard
    //Example blinking LED program
    while(true){
      output_low(LED);
      delay_ms(DELAY);
      output_high(LED);
      delay_ms(DELAY);
    }
}


where I commented out the setup_comparator, because it would give a compiler error as well.

This then builds, but the frequency on the led as measured by oscilloscope is 7.4 KHz.

I can get this to work just fine on an 12F683.

Has anyone else got difficulty to set up the clock on these PICs?

I have a feeling the #use delay(int=4000000) is to blame, because if I modify the program to do nothing but

Code:

void main()
{
    //setup_comparator(NC_NC_NC_NC);// This device COMP currently not supported by the PICWizard
    //Example blinking LED program
    while(true){
      output_low(LED);
      output_high(LED);
    }
}


the LED pin switches at 100KHz. At a 4 MHz clock, this should switch much faster.

Any help at all would be greatly appreciated.
Ttelmah



Joined: 11 Mar 2010
Posts: 19552

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PostPosted: Thu Dec 23, 2010 3:42 pm     Reply with quote

No....

4MHz = 1MIPS.

Each output, involves four instructions (two updating the TRIS, and two updating the output register). Total of 8 instruction times. Then the loop, involves a jump, which is two instruction times, so the expected rate, would be 100KHz exactly. You'd expect the LED to be on for 6uSec, and off for 4uSec.

You are getting exactly the speed expected.

You can improve this to 166KHz, by choosing fast_io, and setting this pin as an output (with a tris statement) before the loop.

The loop would be two instructions faster on a PIC16 chip, in the first case, since these support single instruction bit set/reset operations, not available on the PIC12...

Best Wishes
janbbeck



Joined: 23 Dec 2010
Posts: 7

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PostPosted: Thu Dec 23, 2010 5:13 pm     Reply with quote

Thank you for that. At least I know that I am running at the right clock rate.

Still the delay_ms does not work, and now my number of theories is down to 0.

Any ideas?

Ttelmah wrote:
No....

4MHz = 1MIPS.

Each output, involves four instructions (two updating the TRIS, and two updating the output register). Total of 8 instruction times. Then the loop, involves a jump, which is two instruction times, so the expected rate, would be 100KHz exactly. You'd expect the LED to be on for 6uSec, and off for 4uSec.

You are getting exactly the speed expected.

You can improve this to 166KHz, by choosing fast_io, and setting this pin as an output (with a tris statement) before the loop.

The loop would be two instructions faster on a PIC16 chip, in the first case, since these support single instruction bit set/reset operations, not available on the PIC12...

Best Wishes
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Dec 23, 2010 5:16 pm     Reply with quote

Post your compiler version.
janbbeck



Joined: 23 Dec 2010
Posts: 7

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PostPosted: Thu Dec 23, 2010 5:50 pm     Reply with quote

PCM programmer wrote:
Post your compiler version.

4.114

I also want to point out that delay_us works as advertised, as I just tested on the scope. Delay_ms does not.

if it helps, here is the assembly:


Code:

....................    delay_ms(2);
001C:  MOVLW  02
001D:  MOVLB  00
001E:  MOVWF  25
001F:  GOTO   003
....................       output_low(LED);
0020:  MOVLB  01
0021:  BCF    0C.5
0022:  MOVLB  02
0023:  BCF    0C.5
....................    delay_us(200);
0024:  MOVLW  21
0025:  MOVLB  00
0026:  MOVWF  20
0027:  DECFSZ 20,F
0028:  GOTO   027
....................       output_high(LED);
0029:  MOVLB  01
002A:  BCF    0C.5
002B:  MOVLB  02
002C:  BSF    0C.5
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Dec 24, 2010 1:25 pm     Reply with quote

I looked at the problem using the MPLAB simulator. It actually fails with
delay_us(). If the parameter is 765 or below, the compiler does a simple
loop to count the microseconds. That works OK. But with a delay of 766
or higher, as in
Code:
delay_us(766);

then it doesn't work correctly. It calls a delay routine, and it doesn't work.
The delay_ms() function also doesn't work. It fails with a parameter
of 1 or 1000. I didn't test any more values. These tests were done
with vs. 4.114.

Since delay_us(500) does work, you could create a work-around function
for delay_ms() as shown below. Note: This was only tested at 4 MHz.
Code:

#include <12LF1822.h>
#fuses INTRC_IO, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)

void my_delay_ms(int16 delay)
{
while(delay--)
  {
   delay_us(500);
   delay_us(500);
  }
}

//================================
void main()
{
my_delay_ms(1000);  // 1 second delay

while(1);
}


The problem appears to be fixed in vs. 4.116, so if you have download
rights in effect, you could upgrade. If your download rights just ran out
recently, it's possible that you could report this bug to CCS and maybe
they would give you a free upgrade to 4.116. It's worth trying. But you
have to own the compiler to do this.
janbbeck



Joined: 23 Dec 2010
Posts: 7

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PostPosted: Wed Dec 29, 2010 1:43 pm     Reply with quote

Thanks for looking into this for me, but the delay_ms does not work for me with 4.116 either.

I am planning to use the touch sensor functions, and they use a ms delay as well, so I don't think the work around will do anything for me.

any other ideas?
janbbeck



Joined: 23 Dec 2010
Posts: 7

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PostPosted: Wed Dec 29, 2010 1:47 pm     Reply with quote

scratch my previous post. I had an evironment variable pointing to the old compiler.

4.116 in deed solves the problem.

Thanks again!
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Dec 29, 2010 1:49 pm     Reply with quote

What delay time are you using that fails in vs. 4.116 ?
Post the delay_ms() statement that fails. Also post your #use delay().
janbbeck



Joined: 23 Dec 2010
Posts: 7

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PostPosted: Wed Dec 29, 2010 2:14 pm     Reply with quote

PCM programmer wrote:
What delay time are you using that fails in vs. 4.116 ?
Post the delay_ms() statement that fails. Also post your #use delay().


No, it does work now. Thanks a lot. Now I cannot get the sample code to work that is supposed to do a touch sensing, but I will start a new topic for that.

Thanks again!
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