Ruth Hendrix

Help with my first microcontroller application ever

Discussion created by Ruth Hendrix Employee on Jan 24, 2006
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Posted: Wed Dec 28, 2005 11:04 pm    
 
So I am trying to make an LED blink, and failing at it.

Here is the C code that I have so far.
Code:
#include <MC68HC908KX8.h> void main(void) {   DDRB = 0x01;   TSC = 0x00;   TMODL = 0x00;   TMODH = 0x01;   for(;;) {     __RESET_WATCHDOG();     PTB = 0x01;     while (TSC_TOF == 0);       TSC_TOF = 0;     PTB = 0x01;      while (TSC_TOF == 0);       TSC_TOF = 0;                      }   } 

 
It hangs forever on the fisrt while loop. I don't understand how to use the TMODH and TMODL registers.
 
Posted: Thu Dec 29, 2005 3:20 pm    
 
i think you simply dit not stat the TIM below you see how to init the TIM
(sorry in ASM) but since C is only a better assembler i am shure you will get the idea! Wink
Code:
INI_TIC:                                  ;Initi. OC-Routine         BSET    TRST,TSC             ;TIM-Counter Reset         LDA     TSC                      ;load TIM Status         AND     #%11111000         STA     TSC                      ;PSx = 0         LDA     #$01                     ;load MOD-Register         STA     TMODH         LDA     #$00         STA     TMODL START_TIC:                                ;starts OC         BSET    TOIE,TSC                ;enable TIM TOF-Interrupt (optional)         BCLR    TSTOP,TSC 

 

then your can poll the TOF flag in the TSC register

to clear you have to read TSC first then write 0 to the TOF flag.

Code:
        LDA     TSC                     ;TOF löschen         BCLR    TOF,TSC 

 
Attention: you for HC08 you have to write fist the HI part of a 16 bit register then the Lo part otherwise it will not run!

Saluti
PS. I have uploaded also the EBS08_Qx_CW OS where i use the code abve!
 
Posted: Thu Dec 29, 2005 4:02 pm    
 
G'day,

Quote:
I don't understand how to use the TMODH and TMODL registers.

The 16-bit modulo register setting, represented by TMODH:TMODL, determines the maximum count the timer reaches before overflow occurs, and the count automatically re-starts at zero. For the power-up default value of $FF:FF, this represents 65,536 counts between each overflow condition. For the setting within your program of $01:00, this will represent only 257 counts.

Assuming that you are using the power-up default bus frequency of 1.613 MHz for the 908KX8, you would have a period between timer overflows of about 0.16 milliseconds - somewhat fast to observe the LED blinking.

To provide a flash rate of "hundreds of milliseconds", I would suggest that you leave the modulo setting at the default value, and use a prescale value for the timer greater than 1. For example, a prescale setting of 4 (TSC = 0x02:smileywink: would give a period between overflows of about 160 milliseconds, more appropriate for blinking a LED.

I also see that, within the 'for' loop, you are twice setting PTB0 to a value of 1 (PTB = 0x01:smileywink:, rather than alternating or toggling its state.

I wonder if these are the actual problems, rather than
Quote:
hanging forever on the fisrt while loop
I cannot see an obvious problem with the 'while' loop.

Regards,
 
Posted: Thu Dec 29, 2005 8:04 pm
 
Thanks guys, It works now. Very Happy 

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