Forum: ARM programming with GCC/GNU tools LPC1768 - pulse counter not work

von Mario (Guest)

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Hi, I have to count pulses by LPC1768. I try to use port P0.24 with 
function CAP3.1 to driving Timer3 as counter.

Example of timer3 configuration:
//   counter 3
   const unsigned long TCR_COUNT_RESET = 2, TCR_COUNT_ENABLE = 0x01;
   LPC_SC->PCONP |= (1 << 23);
   LPC_TIM3->CTCR = 0x101;
And port definition:
   LPC_PINCON->PINSEL1 |= (1 << 17) | (1 << 16); // set pin P0.24 as CAP3.1
   LPC_GPIO0->FIODIR &=~(1<<24);         // set pin P0.24 as input
And LPC_TIM3->TC not change.
If I configure Timer3 with PCLK as source is OK. When i use P0.24 as 
input pin is also ok. I can count level changes in main loop. But why 
not work counting pulses by timer/counter functionality?
Maybe I have to match any register more?


von Lutz (Guest)

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>LPC_TIM3->CTCR = 0x101;
0x101 is 0b100000001, but bits 31:4 in CTCR are reserved. You probably 
wanted 0b101, which is 0x5. With that configuration you use CAP3.0 and 
not CAP3.1 as input. If I'm right with my assumption this is a good 
example why one shouldn't use magic numbers in sourcecode and use easy 
readable defines instead (or use bit shifts). Mixing this in one file is 
also a dangerous thing ...

von Vinay K. (vinay_k)

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i want to count external pulses on my LPC1768 board. I configured CTCR 
Register for TIMER 0 on CAP0.0. but my TIMER is not working as a COUNTER 
but its working as TIMER only. i.e. it is taking PCLK as the source & TC 
incrimenting by considering PCLK only. can anybody suggest any solution.


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