#100 Timer0 interrupt
I am trying to use timer0 of a PIC18F97J60 Microcontroller. When the timer overflows I want to start an interrupt service routine. However, the routine I made is never called. I think it has to do with the interrupt number I used. I am using interrupt 1, but I guess it should be interrupt 0. However, if I use interrupt 0, I get following compile error:
**sdcc -mpic16 -p18f97j60 -L/usr/local/lib/pic16 -llibio18f97j60.lib -llibdev18f97j60.lib -llibc18f.a Objects/clock_freq_test.o Objects/LCDBlocking.o
**message: Using default linker script "/usr/local/share/gputils/lkr/18f97j60_g.lkr".
error: More absolute sections use same address: 0 -- "S_clock_freq_test_ivec_0x0_high_isr/ivec_0x0_high_isr", "S_crt0i_entry/entry"
**
So I basically have 2 questions:
- Do I need to use interrupt 0 for timer0 overflow interrupt ?
- If I do need to use interrupt 0, why am I getting this compile error when I use it and how can I solve it ? Is it maybe caused by the way I installed SDCC ? I first installend the newest version, but because this version didn't support type "long long", I installed an older SDCC version provided by my professor with also extra files to support this type. So I actually installed both and didn't remove the latest SDCC version. Do I have to remove it ? And if so, how can I do this ?
By the way, this is the important part of my code that I am trying to fix:
void high_isr (void) interrupt 0
{
LED1_IO = 0;
INTCONbits.T0IE = 0; //disable interrupt
if(INTCONbits.T0IF)
{
LED2_IO ^= 1; //change state of red leds;
INTCONbits.T0IF = 0;
TMR0H = 0x00; //HIGH (0x10000-EXEC_FREQ/1000);
TMR0L = 0x00; //LOW (0x10000-EXEC_FREQ/1000);
T0CONbits.TMR0ON = 0; //disable timer0
INTCONbits.T0IF = 0;
INTCONbits.T0IE = 1; //enable interrupt
T0CONbits.TMR0ON = 1; //enable timer0
}
}
void main(void)
{
LED1_IO = 1;
LED2_IO = 0;
LED1_TRIS = 0; //configure 2nd led pin as output (red)
LED2_TRIS = 0; //configure 3rd led pin as output (red)
/* Timer 0 */ RCONbits.IPEN = 1; TMR0H = 0x00; TMR0L = 0x00; T0CONbits.TMR0ON = 0; //disable timer0 T0CONbits.T08BIT = 0; //use timer0 16-bit counter T0CONbits.T0CS = 0; //use timer0 instruction cycle clock T0CONbits.PSA = 1; //disable timer0 prescaler INTCONbits.T0IF = 0; //clear timer0 overflow bit INTCONbits.T0IE = 1; //enable interrupt INTCON2bits.TMR0IP = 1; // set timer0 high priority T0CONbits.TMR0ON = 1; //enable timer0 while(1) { }
}
Have a look at section "4.6.18.3 Signals" of the manual (
http://sdcc.sourceforge.net/doc/sdccman.pdf). Theres a signal.h header to
deal with interrupts.
Cheers,
Diego
On 1 December 2015 at 22:38, Diego sdiegocc@users.sf.net wrote:
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Support Requests:
#100Diego,
Thanks for the Guide of SDCC. Very useful.
However, it didn't solve my problem. Luckily I could ask today to the professor what was wrong. The error code has to do with the fact that I wrote an interrupt routine for interrupt 0, but somewhere else in the code (I couldn't detect where) there was already an interrupt routine defined for interrupt 0. That's what the "same adress" in the error message means. So I can't write an ISR for interrupt 0.
Anyway, the correct interrupt is interrupt 1. It didn't work in my case because I forgot to enable a bit:
INTCONbits.GIE = 1. // Enable high priority interrupts.
Now it works. Also, don't forget to set timer0 to high priority in order to get an high priority interrupt when Timer0 overflows.
I just add the explanation for people that in future might run against the same problem. I have searched on google for this error message but I couldn't find any reference. So I guess it is usefull for people that in future run against the same error message.
Last edit: Diego 2015-12-02
0 is for reset vector, 1 for high priority interrupts and 2 for low priority interrupts.
FYI, the interrupt 0 you mention somewhere else in the code, is used on the crt0 code which is run before anything else and that's why it's located on the reset vector:
https://sourceforge.net/p/sdcc/code/HEAD/tree/trunk/sdcc/device/lib/pic16/startup/crt0iz.c#l67