configure a general purpose TIMx (x=2,3,4) same as Systick on STM32F103B

[slimbahri]

Posted on March 12, 2010 at 10:33

configure a general purpose TIMx (x=2,3,4) same as Systick on STM32F103B

[Tesla DeLorean]

Posted on May 17, 2011 at 13:43

#define CPUCLOCK (36.0) // CPU Clock MHz

{   int i;   for(i=0; i<10; i++)   {     u32 a, b;     do     {       a = SystemTick; // 1ms counter off SYSTICK interrupt       b = SystemTick;     } while(a == b); // Sychronize on SYSTICK     STOPWATCH_START     Sleep(10); // 10ms delay     STOPWATCH_STOP     printf(''%10d cycles, %7.4lf ms\n'',cyc[1],((1.0 / (CPUCLOCK * 1000.0)) * (double)cyc[1])); // 36 MHz clock, milliseconds from cycles   } }     360091 cycles, 10.0025 ms     360091 cycles, 10.0025 ms     360089 cycles, 10.0025 ms     360089 cycles, 10.0025 ms     360089 cycles, 10.0025 ms     360091 cycles, 10.0025 ms     360175 cycles, 10.0049 ms     360089 cycles, 10.0025 ms     360177 cycles, 10.0049 ms     360177 cycles, 10.0049 ms

[Tesla DeLorean]

Posted on May 17, 2011 at 13:43

>>with the method you suggested, we should using J-TRACE isn't it ? I have only J-LINK;

The cycle counting works with the trace hardware inside the STM32 core, it *does not* require a J-TRACE or J-LINK. It works with stock STM32F103 devices, and probably the rest of the family. If the delay routine is using the SYSTICK at 1 ms, then the 10 ms delay could be between 9-11 ms depending on when you catch the counter. You could always get additional accuracy by using SysTick->VAL which counts down at 1/8000 of a millisecond (assuming 64 MHz, and a /8 prescale, and a 1 ms interrupt) -Clive

[Tesla DeLorean]

Posted on May 17, 2011 at 13:43

Using Timer 4, less resolution/precision, 16-bit register

{   TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;   RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);   TIM_DeInit(TIM4);   TIM_TimeBaseStructure.TIM_Period = 0xffff;   TIM_TimeBaseStructure.TIM_Prescaler = 15;   TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;   TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;   TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure );   //TIM_ARRPreloadConfig(TIM4, ENABLE);   TIM4->EGR |= 0x01; } {   u16 tim[2];   int i;   for(i=0; i<10; i++)   {     u32 a, b;     a = SystemTick;     do     {       b = SystemTick;     } while(a == b);     tim[0] = TIM4->CNT;     TIM4->CR1 |= 1;     Sleep(10);     TIM4->CR1 &= ~1;     tim[1] = TIM4->CNT;     tim[1] = tim[1] - tim[0];     printf(''%10d cycles, %7.4lf ms\n'',tim[1],((16.0 / (CPUCLOCK * 1000.0)) * (double)tim[1]));   }   putchar('\n'); }      22510 cycles, 10.0044 ms      22510 cycles, 10.0044 ms      22511 cycles, 10.0049 ms      22511 cycles, 10.0049 ms      22510 cycles, 10.0044 ms      22511 cycles, 10.0049 ms      22510 cycles, 10.0044 ms      22510 cycles, 10.0044 ms      22511 cycles, 10.0049 ms      22510 cycles, 10.0044 ms

[Tomas DRESLER]

Posted on May 17, 2011 at 13:43

One more argument FOR SysTick:

reading TIMx through APB brings jitter and delay in range (1+ratio) AHB cycles due to resynchronization between APB and AHB in the bridge. Reading systick is done on internal Cortex bus => very low latency, cycle precise. Btw. even if any jitter might be induced, the whole MCU would be delayed with the same amount of time => it's still cycle precise :)

[slimbahri]

Posted on May 17, 2011 at 13:43

Hi Edison,

Would you explain this with more details please?

Slim