Timer in edge count mode

Hello Edesio

Thanks for the code post and very clear instructions on the devices (I wish more users post it the way you have). I will look into it and get back.

Question: Is the USE_PRESCALER defined?

Regards

Amit

Humble outsider enjoyed & commends poster's carefully constructed, detailed (may I say, "template-like") post.  Well done.

Note that the edge-count mode imposes a maximum frequency limit upon your application.  (Fmax = 1/4 System Clock)

The prescaler in edge-count mode, "acts as a timer extension" and (potentially) holds the most significant bits of the count.  Amit did a nice job of identifying a likely, "gotcha" - the (incorrect) setting of, "Prescalar Match" which voids the prescaler.

In your particular application I'd suggest setting this (more precisely) to a (proper) high, 16 bit value - so that inadvertent/unwanted prescale roll-over/clears do not result...  And - while the wide timer may count up or down - the "up" direction seems so much simpler and intuitive... (prescaler thus contains the number of 32 bit roll-overs - i.e. msb)

One last comment - as good as your post was - multiple, other timers appeared w/in your code listing.  This forces extra care/attention upon your reviewers - not ideal here - nor in the workplace - where reviewer ease/efficiency is valued...  Superior method may be to, "quarantine" all other timer code - so that, "just the timer under examination" is highlighted for ease of analysis...  (i.e. method borrowed/stolen from surgical, "draping" - show just the area of interest to insure tight focus...)

Hi!

I set the clock frequency to the maximum (80 MHz) to be on the safe side for a 10 MHz OCXO input clock.

I will load the prescaler match register to 0xFFFF to avoid this roll over problem.

The code from PortFunctionInit was generated by the PinMux utility and I left it as is. Also I did previous tests using "narrow" timers to check this prescaler "detail" and failed to remove this part.

Sorry.

Edesio

Hello Amit!

Thanks for your insight. It worked like a charm!

I cut, pasted and changed TimerPrescaleMatchGet into this:

#include "inc/hw_timer.h"

static uint32_t
TimerPrescaleValue(uint32_t ui32Base, uint32_t ui32Timer)
{
//
// Check the arguments.
//
ASSERT(_TimerBaseValid(ui32Base));
ASSERT((ui32Timer == TIMER_A) || (ui32Timer == TIMER_B) ||
(ui32Timer == TIMER_BOTH));

//
// Return the appropriate prescale value.
//
return((ui32Timer == TIMER_A) ? HWREG(ui32Base + TIMER_O_TAPV) :
HWREG(ui32Base + TIMER_O_TBPV));
}

Changed the main loop to:

while (1)
{
val = TimerValueGet(WTIMER0_BASE, TIMER_A);
// pre = TimerPrescaleGet(WTIMER0_BASE, TIMER_A);
pre = TimerPrescaleValue(WTIMER0_BASE, TIMER_A);
UARTprintf("Timer0A: (%u, %u)\n", pre, (val & 0xFFFFFFFF));
}

And got:

Ready> 

Timer0A: (0, 23199203)
Timer0A: (0, 131308671)
Timer0A: (0, 908645345)
Timer0A: (0, 1870071501)
Timer0A: (0, 3190067475)
Timer0A: (0, 3295295085)
Timer0A: (0, 3717733072)
Timer0A: (0, 4102671586)
Timer0A: (1, 31213275)
Timer0A: (1, 3544148393)
Timer0A: (1, 4084836312)
Timer0A: (2, 165877558)

Thanks again. Now back to the hardware part :-)

Edesio

P.S.: Should I post the whole revised code?

Hello Edesio

Yes, issues when migrating code from narrow timer to wide timer has it's subtleties. Good that we figured it fast to ungate the development.

Regards

Amit

Hello, I need to count frequency with TM4C129ENCPDT. I tried the above code but I am running in some trouble.

First, when I do

#define USE_PRESCALER

and

TimerConfigure(TIMER0_BASE, TIMER_CFG_SPLIT_PAIR | TIMER_CFG_A_CAP_COUNT_UP | TIMER_CFG_B_CAP_COUNT_UP);

then the whole processor runs about 2x faster! I use TI-RTOS and any Task_sleep() lasts only about half of the specified period. Which is very weird. I use 25MHz crystal and 120MHz cpu frequency. How can Timer configuration affect the system frequency?

The other problem is with the configuration of timers themselves. I need to use pins T0CCP0, T0CCP1, T2CCP0 and T2CCP1. At each input I have a wave with fixed positive pulse duration of 18us. Maximum expected frequency is about 6kHz. I need to measure those four frequencies.

For some reason, the last bit in timer A Mode register

(HWREG(TIMER0_BASE + TIMER_O_TAMR) 
(HWREG(TIMER2_BASE + TIMER_O_TAMR) 

of T0CCP0 and T2CCP0, which are timer A in both cases, is set to zero, no matter what I do. Per datasheet that means they are configured to 0x2 Periodic TImer mode. I need it to be 0x3 Capture mode.

The datasheet says at page 1097:

GPTM Timer A Mode
The TAMR values are defined as follows:

Value Description
0x0 Reserved
0x1 One-Shot Timer mode
0x2 Periodic Timer mode
0x3 Capture mode

The Timer mode is based on the timer configuration defined by bits 2:0
in the GPTMCFG register.

But GPTMCFG is set correctly!

The B timers are seemingly configured correctly, but they do not count, value is always zero.

What am I doing wrong?

The init sequence:

void EK_TM4C129EXL_initTIMER(void)
{
	//#define USE_PRESCALER
	SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0); //IMP1, IMP2
	SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER2); //IMP3, IMP4

	//IMP1
	GPIOPinConfigure(GPIO_PL5_T0CCP1);
	GPIOPinTypeTimer(GPIO_PORTL_BASE, GPIO_PIN_5);

	//IMP2
	GPIOPinConfigure(GPIO_PL4_T0CCP0);
	GPIOPinTypeTimer(GPIO_PORTL_BASE, GPIO_PIN_4);

	//IMP3
	GPIOPinConfigure(GPIO_PM0_T2CCP0);
	GPIOPinTypeTimer(GPIO_PORTM_BASE, GPIO_PIN_0);

	//IMP4
	GPIOPinConfigure(GPIO_PM1_T2CCP1);
	GPIOPinTypeTimer(GPIO_PORTM_BASE, GPIO_PIN_1);

	//enable pull-downs
	/*
	GPIOPadConfigSet(GPIO_PORTL_BASE, GPIO_PIN_5, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD_WPD);
	GPIOPadConfigSet(GPIO_PORTL_BASE, GPIO_PIN_4, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD_WPD);
	GPIOPadConfigSet(GPIO_PORTM_BASE, GPIO_PIN_0, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD_WPD);
	GPIOPadConfigSet(GPIO_PORTM_BASE, GPIO_PIN_1, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD_WPD);
	 */
	//IMP1, IMP2
	#if defined(USE_PRESCALER)
	TimerConfigure(TIMER0_BASE, TIMER_CFG_SPLIT_PAIR | TIMER_CFG_A_CAP_COUNT_UP | TIMER_CFG_B_CAP_COUNT_UP);
	#else
	TimerConfigure(TIMER0_BASE, TIMER_CFG_A_CAP_COUNT_UP);
	TimerConfigure(TIMER0_BASE, TIMER_CFG_B_CAP_COUNT_UP);
	#endif

	TimerControlEvent(TIMER0_BASE, TIMER_A, TIMER_EVENT_POS_EDGE);
	TimerControlEvent(TIMER0_BASE, TIMER_B, TIMER_EVENT_POS_EDGE);
/*
    TimerLoadSet(TIMER0_BASE, TIMER_A, 0xFFFE);
    TimerMatchSet(TIMER0_BASE, TIMER_A, 0x00);
    TimerLoadSet(TIMER0_BASE, TIMER_B, 0xFFFE);
    TimerMatchSet(TIMER0_BASE, TIMER_B, 0x00);
*/
/*
    TimerPrescaleMatchSet(TIMER0_BASE, TIMER_A, 0xFFFF-1);
	TimerPrescaleMatchSet(TIMER0_BASE, TIMER_B, 0xFFFF-1);
*/
	TimerEnable(TIMER0_BASE, TIMER_BOTH);

	//IMP3, IMP4
	#if defined(USE_PRESCALER)
	TimerConfigure(TIMER2_BASE, TIMER_CFG_SPLIT_PAIR | TIMER_CFG_A_CAP_COUNT_UP | TIMER_CFG_B_CAP_COUNT_UP);
	#else
	TimerConfigure(TIMER2_BASE, TIMER_CFG_A_CAP_COUNT_UP);
	TimerConfigure(TIMER2_BASE, TIMER_CFG_B_CAP_COUNT_UP);
	#endif

	TimerControlEvent(TIMER2_BASE, TIMER_A, TIMER_EVENT_POS_EDGE);
	TimerControlEvent(TIMER2_BASE, TIMER_B, TIMER_EVENT_POS_EDGE);

/*
    TimerLoadSet(TIMER2_BASE, TIMER_A, 0xFFFE);
    TimerMatchSet(TIMER2_BASE, TIMER_A, 0x00);
    TimerLoadSet(TIMER2_BASE, TIMER_B, 0xFFFE);
    TimerMatchSet(TIMER2_BASE, TIMER_B, 0x00);
*/
/*
	TimerPrescaleMatchSet(TIMER2_BASE, TIMER_A, 0xFFFF-1);
	TimerPrescaleMatchSet(TIMER2_BASE, TIMER_B, 0xFFFF-1);
*/
	TimerEnable(TIMER2_BASE, TIMER_BOTH);

}