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add comments about TIMER modes and set TIMER2 off by default

pull/7175/head
Qinghao Shi 2018-06-15 16:26:00 +01:00
parent 3ba635d233
commit 43242589de
1 changed files with 10 additions and 5 deletions
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15
targets/TARGET_ARM_FM/TARGET_FVP_MPS2/us_ticker.c
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@ -25,9 +25,15 @@
* with interrupt fired counter reaches 0.
*
* So 2 Timers are used to construct mbed OS HAL ticker.
*
* TIMER1 is for counting, and returns inverted binary when read from it
* TIMER2 is for generate interrupts
* TIMER1 will be kept in free-running mode (default, and not generate interrupts)
*
* TIMER2 is for generating interrupts
* So TIMER2 is set to periodic mode, which start decrement counting form LOADVALUE generates interrupts at 0
* and TIMER2 also set into one-shot mode, which counter halts when is reaches 0
*/
static int us_ticker_inited = 0;
void us_ticker_init(void)
@ -50,11 +56,9 @@ void us_ticker_init(void)
US_TICKER_TIMER2->TimerControl |= 0x1 << CMSDK_DUALTIMER2_CTRL_PRESCALE_Pos; // set TIMER2 with 4 stages prescale
US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_MODE_Msk; // set TIMER2 periodic mode
US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_ONESHOOT_Msk; // set TIMER2 one-shot mode
US_TICKER_TIMER1->TimerControl |= CMSDK_DUALTIMER1_CTRL_EN_Msk; // enable TIMER1 counter
US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_EN_Msk; // enable TIMER2 counter
NVIC_SetVector(US_TICKER_TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
us_ticker_inited = 1;
@ -76,7 +80,7 @@ uint32_t us_ticker_read()
void us_ticker_set_interrupt(timestamp_t timestamp)
{
uint32_t delta = timestamp - us_ticker_read();
US_TICKER_TIMER2->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_EN_Msk; // disable TIMER2
US_TICKER_TIMER2->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_EN_Msk; // disable TIMER2
US_TICKER_TIMER2->TimerLoad = delta; // Set TIMER2 load value
US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_INTEN_Msk; // enable TIMER2 interrupt
US_TICKER_TIMER2->TimerControl |= CMSDK_DUALTIMER2_CTRL_EN_Msk; // enable TIMER2 counter
@ -93,6 +97,7 @@ void us_ticker_fire_interrupt(void)
void us_ticker_disable_interrupt(void)
{
US_TICKER_TIMER2->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_INTEN_Msk;
US_TICKER_TIMER2->TimerControl &= ~CMSDK_DUALTIMER2_CTRL_EN_Msk; // disable TIMER2
NVIC_DisableIRQ(US_TICKER_TIMER_IRQn);
}
@ -104,7 +109,7 @@ void us_ticker_clear_interrupt(void)
const ticker_info_t *us_ticker_get_info(void)
{
static const ticker_info_t info = {
1562500, // 4 stages prescale from 25MHz (dived by 16)
1562500, // 4 stages prescaled from 25MHz (dived by 16)
32 // 32 bit counter
};
return &info;