Timer set-up problem LPC 1769

[lpcware]

Content originally posted in LPCWare by Fabienvg on Wed Oct 09 08:06:14 MST 2013
Hello,

I'm really new to microcontrollers. I tried to set up a timer for the LPC 1769 with interrupt, but I think I'm doing something wrong. For example the prescaler. I set it to 1000-1 AND it looks like, when I test my program,  it is set to 1 ms, but I can't imagine it works on only 1 Mhz. I think I'm doing things wrong in the basic configuration. Anyone who can help me out setting up a basic configuration for the timer and interrupt would help me a ton.

User manual: http://www.nxp.com/documents/user_manual/UM10360.pdf

Basic timer configuration starts at page 490.

#define TMR16B0TC  0x40004008
#define PCLKSEL0                  0x400FC1A8
#define TMR16B0IR 0x40004000
#define TMR16B0TCR 0x40004004
#define TMR16B0PR 0x4000400C
#define TMR16B0MR0 0x40004018
#define TMR16B0MCR          0x40004014
#define TMR16B0CTCR         0x40004070
#define PCONP 0x400FC0C4
#define ISER0 0xE000E100

int* pCLKSEL0        = (int*) PCLKSEL0;
int* tMR16B0TCR = (int*) TMR16B0TCR;
int* tMR16B0PR = (int*) TMR16B0PR;
int* tMR16B0MR0 = (int*) TMR16B0MR0;
int* tMR16B0MCR = (int*) TMR16B0MCR;
int* tMR16B0CTCR = (int*) TMR16B0CTCR;
int* tMR16B0IR = (int*) TMR16B0IR;
int* iSER0 = (int*) ISER1;
int* tMR16B0TC = (int*) TMR16B0TC;
int* pCONP = (int*) PCONP;

void (*timer_tmr_callback)();

void init()
{
*pCONP = 0x2; 
*pCLKSEL0    = 0xC;
*tMR16B0TC   = 0x0;
*tMR16B0PR     = 1000 - 1;
*tMR16B0CTCR    = 0;
*tMR16B0MR0 = 1000;
*tMR16B0MCR     = 0x05;
}

void timer_async_usec( unsigned int msec, void (*callback)())
{
timer_tmr_callback     = callback;
*tMR16B0MR0    = msec;
*tMR16B0MCR           = 0x07;
*iSER0    = (1 << 1);
*tMR16B0TCR    = 0x2;
*tMR16B0TCR    = 0x1;
}

void (TIMER0_IRQHandler(void))
{
*tMR16B0IR = 0x1F;
timer_tmr_callback();
}

[lpcware]

Content originally posted in LPCWare by Pacman on Mon Oct 28 16:03:28 MST 2013
Now, I changed your code, so it can be used with the header files from NXP (and ARM):

#include "lpc175x_6x.h"
#include "lpc17xx_clkpwr.h"

void (*timer_tmr_callback)();

#define CLKPWR_PCLKSEL_CCLK_DIV_8((uint32_t)(3))/* Ahem.. This definition seems to be missing from the include files. */

void init()
{
LPC_SC->PCONP = CLKPWR_PCONP_PCTIM0;/* NOTE: Turn off EVERYTHING but timer0! */
LPC_SC->PCLKSEL0 = CLKPWR_PCLKSEL_SET(CLKPWR_PCLKSEL_TIMER0, CLKPWR_PCLKSEL_CCLK_DIV_8);
LPC_TIM0->TC = 0x0;
LPC_TIM0->PR = 1000 - 1;
LPC_TIM0->CTCR = 0;
LPC_TIM0->MR0 = 1000;
LPC_TIM0->MCR = TIM_INT_ON_MATCH(0) | TIM_STOP_ON_MATCH(0);
}

void timer_async_usec( unsigned int msec, void (*callback)())
{
timer_tmr_callback = callback;
LPC_TIM0->MR0 = msec;
LPC_TIM0->MCR = TIM_INT_ON_MATCH(0) | TIM_RESET_ON_MATCH(0) | TIM_STOP_ON_MATCH(0);
NVIC->ISER[1] = (1 << TIMER0_IRQn);/* using NVIC_EnableIRQ(TIMER0_IRQn); won't hurt */
LPC_TIM0->TCR = TIM_RESET;
LPC_TIM0->TCR = TIM_ENABLE;
}

void (TIMER0_IRQHandler(void))
{
LPC_TIM0->IR = 0x1F;/* note: NXP clears all 32 bits; I suggest using LPC_TIM0->IR = ~0; */
timer_tmr_callback();
}

It's not tested. But as I wrote earlier, I think you want to change your peripheral clock divider for the timer.

[lpcware]

Content originally posted in LPCWare by rocketdawg on Mon Oct 28 08:12:31 MST 2013

---

Quote: Pacman
First off all, download the libraries  - or git clone http://git.lpcware.com/(libname).

The libraries are distributed as source-code, and you can easily find out how to do things by looking in these sources. (Believe me, you will want to use the libraries!)

---

Yes.  And the libraries will have useful defined names for all the magic numbers that are in the code.
Try modifying that code a few months from now!   Who knows what
*iSER0 = (1 << 1);
means?  Have to look up the hardware reference.

[lpcware]

Content originally posted in LPCWare by Pacman on Sun Oct 27 21:18:50 MST 2013
First off all, download the libraries  - or git clone http://git.lpcware.com/(libname).

The libraries are distributed as source-code, and you can easily find out how to do things by looking in these sources. (Believe me, you will want to use the libraries!)

Second: It's not always a good idea to declare something 'int'.
An 'int' can be any size. 8, 16, 32 or 64 bit; the compiler may choose whatever it wants.

You may want to check your CPU clock frequency.
Is it running on the internal clock frequency ?
Is it using a PCLK/4 or PCLK/8 ?
-That could make your timer run at something that feels like 1MHz.

Note: If you used the libraries, your code would be much more readable for people in this forum, which means you would probably get a reply faster.