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[NUCLEO_F103RB] Timer fixes 

- the timer data structures were not properly initialized
- changed slave timer mode to external clock 1 (section 15.3.15 of the manual)
- avoid a possible race condition when concatenating the values of the
  two 16-bit timers
pull/122/head
Bogdan Marinescu 2013-12-07 14:26:54 +02:00
parent 1dbb6d9c90
commit 2b8e05e002
1 changed files with 17 additions and 4 deletions
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21
libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/us_ticker.c
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@ -33,6 +33,7 @@ void us_ticker_init(void) {
// Time base configuration
// TIM1 is used as "master", "TIM4" as "slave". TIM4 is clocked by TIM1.
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Period = 0xFFFF;
TIM_TimeBaseStructure.TIM_Prescaler = (uint16_t)(SystemCoreClock / 1000000) - 1; // 1 µs tick
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
@ -42,6 +43,7 @@ void us_ticker_init(void) {
TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);
// Master timer configuration
TIM_OCStructInit(&TIM_OCInitStructure);
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = 0;
@ -51,7 +53,7 @@ void us_ticker_init(void) {
TIM_SelectOutputTrigger(TIM1, TIM_TRGOSource_Update);
// Slave timer configuration
TIM_SelectSlaveMode(TIM4, TIM_SlaveMode_Gated);
TIM_SelectSlaveMode(TIM4, TIM_SlaveMode_External1);
TIM_SelectInputTrigger(TIM4, TIM_TS_ITR0);
// Enable timers
@ -60,10 +62,21 @@ void us_ticker_init(void) {
}
uint32_t us_ticker_read() {
uint32_t counter;
uint32_t counter, counter2;
if (!us_ticker_inited) us_ticker_init();
counter = (uint32_t)((uint32_t)TIM_GetCounter(TIM4) << 16) + (uint32_t)TIM_GetCounter(TIM1);
return counter;
// A situation might appear when TIM1 overflows right after TIM4 is read and before the
// new (overflowed) value of TIM1 is read, which would make the code below consider the
// previous (incorrect) value of TIM4 and the new value of TIM1, which would return a
// value in the past. Avoid this by computing consecutive values of the timer until they
// are properly ordered.
counter = counter2 = (uint32_t)((uint32_t)TIM_GetCounter(TIM4) << 16) + (uint32_t)TIM_GetCounter(TIM1);
while (1) {
counter2 = (uint32_t)((uint32_t)TIM_GetCounter(TIM4) << 16) + (uint32_t)TIM_GetCounter(TIM1);
if (counter2 > counter)
break;
counter = counter2;
}
return counter2;
}
void us_ticker_set_interrupt(unsigned int timestamp) {