Lpc2000

Sten wrote:
> Herbert Demmel wrote:
> 
>>Hi,
>>
>>I seem to miss something with setting up PWM5 output - the routine below 
>>sometimes works, sometimes not (depending non additional code - this 
>>versions below currentlly does NOT work).
>>
>>Any idea what I miss to setup?
>>
>>Thanks for your input.
>>
>>Regards
>>Herbert
>>
>>#include <LPC213x.H>                    /* LPC213x definitions  */
>>
>>#define TICKS_PER_US            15
>>
>>void io_alarm_out(unsigned int freq)
>>{
> 
> 
> 	PWMTCR = (1ul << 0) | (1ul << 1);	/* Enter reset state and force counter to zero*/
> 
> 
>>         // match register 0 controls the cycle frequency
>>         PWMMR0 = 1000000 * TICKS_PER_US / freq;
>>
>>         // we want to have a duty cycle of 50% so always set PWMMR5 to 
>>half of PWMMR0
>>         PWMMR5 = PWMMR0 / 2;
>>
>>         // enable PWM5 output
>>         PWMPCR |= (0x01 << 13);
> 
> 
> 	PWMTCR = (1ul << 0) | (1ul << 3);	/* Re-enable PWM */
> 
> 
>>}
>>
>>int main(void)
>>{
>>         // --- PWM5 setup ---
>>
>>         // Enable P0.21 to be PWM5
>>         PINSEL1 |= (0x01 << 10);
>>         PWMTCR = 1;             // enable PWM timer, let shadow register 
>>disabled
>>
>>         // reset PWM timer when PWMMR0 matches
> 
>         //  PWMMCR = 0x2;
> 
>>         // gives 1000Hz
>>         io_alarm_out(1000);
>>
>>         while (1)
>>                 ;
>>}
>>
> 
> 
> Hallo Herbert,
> 
> Mmmmh, don't you need to turn on PWM module in PCONP? Or do you let all peripherials active on
> startup by default?
> 
> But bit #3 in PWMTCR enables PWM module. Description of this bit says:
> "When one, PWM mode is enabled. PWM mode causes shadow registers..." (2294's datasheet, p.233)
> 
> After you have enabled PWM module (if bit #3 in PWMTCR is set) and set up a value in a PWMMRx
> register you just need to set the appropriated bit in PWMLER register to take effect of new PWMMRx
> value.
> 
> You do not need using PWMLER register if you hold PWM in reset state during changing PWMMRx values
> (see changes above).
> 
> Try it!
>   Sten
> 

Oooops, sorry! Do not comment PWMMCR in main(). But you can uncomment PWMTCR statement instead.

  Sten

-- 
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