Chief Delphi - Timer interrupt hic-cupping

Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Programming (http://www.chiefdelphi.com/forums/forumdisplay.php?f=51)

- - Timer interrupt hic-cupping - HELP (http://www.chiefdelphi.com/forums/showthread.php?t=26778)

Timer interrupt hic-cupping - HELP

Trying to set up a 32-bit 10Mhz timer...

I initialized Timer1 like this:

Code:

volatile unsigned int tmsClock = 0;

 

void Initialize_Timer_1(void)  

{

 TMR1L = 0x00;  

 TMR1H = 0x00;

   

 T1CONbits.T1CKPS0 = 0; // 1:1 prescaler 10Mhz

 T1CONbits.T1CKPS1 = 0; 

 T1CONbits.T1OSCEN = 0; // oscillator disabled

 T1CONbits.TMR1CS = 0; // use the internal clock

 T1CONbits.RD16 = 1; // timer 1 register operations are done in one 16-bit access



 PIE1bits.TMR1IE = 1; // Enable interrupt on overflow 

 IPR1bits.TMR1IP = 0; // overflow interrupt is low priority 

 T1CONbits.TMR1ON = 1; // Timer 1 is enablED

}



void Timer_1_Int_Handler(void)

{

 // this function will be called when a timer 1 interrupt occurs

  tmsClock++;

}

The handler simply increments a 16-bit counter, every 0.00655 seconds, which rolls over every 429.49 seconds. Then, I wrote these functions to fetch the 32bit snapshot of the timer:

Code:

unsigned int GetTick(void)  //Gets 16-bit timer value

{

   unsigned char Temp_Buf; // 8-bit temporary buffer

   unsigned int Timer_Snapshot; // 16-bit variable



   Temp_Buf = TMR1L; // TMR1L must be read before TMR1H

   Timer_Snapshot = TMR1H;

   Timer_Snapshot <<= 8; // move TMR1H data to the upper half of the variable

   Timer_Snapshot += Temp_Buf; // we now have all sixteen bits  



   return Timer_Snapshot;

}



unsigned long GetTime(void) //Gets 32-bit timer value

{

   unsigned long ThisTick;

   ThisTick=tmsClock;

   ThisTick <<= 16;                  //Mutliply by 65536

   ThisTick += GetTick();  //Add timer snapshot

   return ThisTick;

}

Now GetTime() works as intended, except every second or two I get a strange (really large) value returned. Any ideas?

BTW: I discovered this error around 3:00am on ship day, which was wreaking havoc on our autonomuous code. Without a controller to test on, I haven't been able to trace the problem.

Re: Timer interrupt hic-cupping - HELP

Quote:

Originally Posted by roknjohn

Trying to set up a 32-bit 10Mhz timer...

I initialized Timer1 like this:
...
The handler simply increments a 16-bit counter, every 0.00655 seconds, which rolls over every 429.49 seconds. Then, I wrote these functions to fetch the 32bit snapshot of the timer:
...
Now GetTime() works as intended, except every second or two I get a strange (really large) value returned. Any ideas?

BTW: I discovered this error around 3:00am on ship day, which was wreaking havoc on our autonomuous code. Without a controller to test on, I haven't been able to trace the problem.

YOU SHIPPED YOUR CONTROLLER?!?!? You still have your EDU, right?

In GetTick(), why not just set Timer_Snapshot to tmsClock? Doesn't the interupt go off every tick? or just on overflow?

Re: Timer interrupt hic-cupping - HELP

Quote:

Originally Posted by roknjohn

Now GetTime() works as intended, except every second or two I get a strange (really large) value returned. Any ideas?

Define really large. As do you think the error is in the high 16 bit or the low 16?

Re: Timer interrupt hic-cupping - HELP

Quote:

Define really large. As do you think the error is in the high 16 bit or the low 16?

Well, that's a good question. It appeared to be in the high 16 bits of the GetTime() result. My trace output code looked like this:

Code:

 

printf("clock=%6d\n",tmsClock);

printf("timer=%lx\n",(unsigned long) GetTime());

The tmsClock value always looked okay. The GetTime() would accend as expected but I would get some "noise" in the high 16 bits.

Since my terminal program converted the hexstring to decimal, I wasn't able to issolate it to ONLY the high 16.

Re: Timer interrupt hic-cupping - HELP

Printf expects signed ints. Use the other guy's lib. (See Getting Long Data)

Re: Timer interrupt hic-cupping - HELP

Quote:

Originally Posted by roknjohn

Code:

 

printf("timer=%lx\n",(unsigned long) GetTime());

I agree with Jamie, this printf will return bogus results. It only processes 16 bits and treats them as a signed int.

[edit]My error. I forgot about the %lx format being available in printf. Our original issue with printing longs was with interpreting signed longs easily. Thanks for the correction Random.

Re: Timer interrupt hic-cupping - HELP

Quote:

Originally Posted by Mark McLeod

I agree with Jamie, this printf will return bogus results. It only processes 16 bits and treats them as a signed int.

No, the %lx directive supports longs.

Though, as to the orignial question, I think it may be a critical section problem, where the interrupt code is running during a critical part of the main code. Specifically:

ThisTick=tmsClock;

That line actually compiles to about 10 lines of assembly. If the interrupt occurs during that section, really odd things can happen. You may need to disable interrupts right before that, and reenable them right after it.

[edit] Further thought on this (and clarification as to the actual problem) makes me realize that this wouldn't occur quite that often.[/edit

Re: Timer interrupt hic-cupping - HELP

Here is the ouput using the EDU controller: (I only output a line every 5th program loop) I marked lines that contain errors with asteriks.

Code:



IFI User Processor Initialized ...

GetTime() = edb4f  tmsClock =         15

GetTime() = 1bd3cc  tmsClock =         28

GetTime() = 28cc4b  tmsClock =         41

GetTime() = 35c4c1  tmsClock =         54

GetTime() = 42bd32  tmsClock =         67

GetTime() = 4fb5b7  tmsClock =         79

GetTime() = 5cae32  tmsClock =         92

GetTime() = 69a6a8  tmsClock =        105

GetTime() = 769f21  tmsClock =        118

GetTime() = 83979a  tmsClock =        131

GetTime() = 909018  tmsClock =        144

GetTime() = 9d8894  tmsClock =        157

GetTime() = aa8109  tmsClock =        170

GetTime() = b77980  tmsClock =        183

GetTime() = c47201  tmsClock =        196

GetTime() = d16a78  tmsClock =        209

GetTime() = de62f5  tmsClock =        222

GetTime() = eb5b76  tmsClock =        235

GetTime() = f853f0  tmsClock =        248

GetTime() = 1054c66  tmsClock =        261

GetTime() = 11244e1  tmsClock =        274

GetTime() = 11f3d62  tmsClock =        287

GetTime() = 12c35db  tmsClock =        300

GetTime() = 1392e5a  tmsClock =        313

GetTime() = 14626d7  tmsClock =        326

GetTime() = 1531f4e  tmsClock =        339

GetTime() = 16017d1  tmsClock =        352

GetTime() = 16d104a  tmsClock =        365

GetTime() = 17a8cf  tmsClock =        378  *****

GetTime() = 187181  tmsClock =        391  *****

GetTime() = 193f9bd  tmsClock =        404

GetTime() = 1a0f239  tmsClock =        417

GetTime() = 1adeab2  tmsClock =        430

GetTime() = 1bae32f  tmsClock =        443

GetTime() = 1c7dba8  tmsClock =        456

GetTime() = 1d4d425  tmsClock =        469

GetTime() = 1e1cca0  tmsClock =        482

GetTime() = 1eec51b  tmsClock =        495

GetTime() = 1fbbd96  tmsClock =        508

GetTime() = 208b611  tmsClock =        521

GetTime() = 215ae8c  tmsClock =        533

GetTime() = 222a707  tmsClock =        546

GetTime() = 22f9f83  tmsClock =        559

GetTime() = 23c97f9  tmsClock =        572

GetTime() = 249907c  tmsClock =        585

GetTime() = 25688fd  tmsClock =        598

GetTime() = 2638172  tmsClock =        611

GetTime() = 27079ee  tmsClock =        624

GetTime() = 27d7263  tmsClock =        637

GetTime() = 28a6ae6  tmsClock =        650

GetTime() = 2976363  tmsClock =        663

GetTime() = 2a45bdc  tmsClock =        676

GetTime() = 2b1545e  tmsClock =        689

GetTime() = 2be4cd5  tmsClock =        702

GetTime() = 2cb4554  tmsClock =        715

GetTime() = 2d83dcb  tmsClock =        728

GetTime() = 2e5364a  tmsClock =        741

GetTime() = 2f22ec5  tmsClock =        754

GetTime() = 2ff2740  tmsClock =        767

GetTime() = 30c1fb2  tmsClock =        780

GetTime() = 319182a  tmsClock =        793

GetTime() = 32610b1  tmsClock =        806

GetTime() = 33392a  tmsClock =        819   *****

GetTime() = 3401e4  tmsClock =        832   *****

GetTime() = 34cfa20  tmsClock =        845

GetTime() = 359f29d  tmsClock =        858

GetTime() = 366eb16  tmsClock =        871

GetTime() = 373e393  tmsClock =        884

GetTime() = 380dc08  tmsClock =        897

GetTime() = 38dd489  tmsClock =        910

GetTime() = 39acd02  tmsClock =        923

GetTime() = 3a7c57f  tmsClock =        936

GetTime() = 3b4bdf9  tmsClock =        949

GetTime() = 3c1b66b  tmsClock =        962

GetTime() = 3ceaeea  tmsClock =        974

GetTime() = 3dba761  tmsClock =        987

GetTime() = 3e89fe0  tmsClock =   1000

GetTime() = 3f59861  tmsClock =   1013

GetTime() = 40290d6  tmsClock =   1026

GetTime() = 40f8957  tmsClock =   1039

GetTime() = 41c81cb  tmsClock =   1052

GetTime() = 4297a4d  tmsClock =   1065

GetTime() = 43672c2  tmsClock =   1078

GetTime() = 4436b43  tmsClock =   1091

GetTime() = 45063b7  tmsClock =   1104

GetTime() = 45d5c3d  tmsClock =   1117

GetTime() = 46a54b8  tmsClock =   1130

GetTime() = 4774d2f  tmsClock =   1143

GetTime() = 48445a4  tmsClock =   1156

GetTime() = 4913e25  tmsClock =   1169

GetTime() = 49e36a4  tmsClock =   1182

GetTime() = 4ab2f1f  tmsClock =   1195

GetTime() = 4b82795  tmsClock =   1208

GetTime() = 4c5200e  tmsClock =   1221

GetTime() = 4d21889  tmsClock =   1234

GetTime() = 4df110c  tmsClock =   1247

GetTime() = 4ec98c  tmsClock =   1260   *****

GetTime() = 4f9245  tmsClock =   1273   *****

GetTime() = 505fa7c  tmsClock =   1286

GetTime() = 512f2f7  tmsClock =   1299

It looks like the last hex digit is being dropped every so often.

Re: Timer interrupt hic-cupping - HELP

Quote:

Originally Posted by roknjohn

Here is the ouput using the EDU controller: (I only output a line every 5th program loop) I marked lines that contain errors with asteriks.

Code:



GetTime() = 16017d1  tmsClock =      352

GetTime() = 16d104a  tmsClock =      365

GetTime() = 17a8cf  tmsClock =        378  *****

GetTime() = 187181  tmsClock =        391  *****

It looks like the last hex digit is being dropped every so often.

Actually it's not the last one... the output you should be getting is

GetTime() = 016017d1 tmsClock = 352
GetTime() = 016d104a tmsClock = 365
GetTime() = 017a08cf tmsClock = 378 *****
GetTime() = 01870181 tmsClock = 391 *****

Notice the extra 0's. The problem is the printf function doesn't zero pad the output like it should. That is 'ok' for the ints, but for the longs it causes problems (In the printf lib, the printi function actually gets called twice for longs. once for each word.)

Re: Timer interrupt hic-cupping - HELP

You are right. Thanks for pointing that out.

It appears the timer is actually working correctly. Well, that's one less thing to worry about. Now, back to other things.