From dd52d66d034c943380d4a95d7677cff7772109df Mon Sep 17 00:00:00 2001 From: bnewbold Date: Fri, 2 Jul 2010 00:57:35 -0400 Subject: timers progress examples code cleanup, more descriptive comments, more notes --- libmaple/timers.c | 57 +++++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 45 insertions(+), 12 deletions(-) (limited to 'libmaple') diff --git a/libmaple/timers.c b/libmaple/timers.c index a772cf9..daf8b51 100644 --- a/libmaple/timers.c +++ b/libmaple/timers.c @@ -75,15 +75,17 @@ typedef struct { uint16 RESERVED19; } Timer; - +// These are the output compare interrupt functions that get called by the +// handlers below volatile static voidFuncPtr timer1_handlers[4]; volatile static voidFuncPtr timer2_handlers[4]; volatile static voidFuncPtr timer3_handlers[4]; volatile static voidFuncPtr timer4_handlers[4]; +// This function should probably be rewriten to take (timer_num, mode) and have +// prescaler set elsewhere. The mode can be passed through to set_mode at the +// end void timer_init(uint8 timer_num, uint16 prescale) { - // This initialization is very PWM-specific. That's a good default but it - // should probably call down to a set_mode function Timer *timer; uint8 is_advanced = 0; @@ -151,9 +153,11 @@ void timer_init(uint8 timer_num, uint16 prescale) { timer->CR1 |= 1; // Enable timer } -void timer_set_count(uint8 timer_num, uint16 value) { - Timer *timer; - ASSERT(timer_num > 0 && timer_num <= 4); +// This function sets the counter value via register for the specified timer. +// Can't think of specific usecases except for resetting to zero but it's easy +// to implement and allows for "creative" programming +void timer_set_count(uint8 timer_num, uint16 value) { Timer *timer; +ASSERT(timer_num > 0 && timer_num <= 4); switch(timer_num) { case 1: @@ -172,6 +176,8 @@ void timer_set_count(uint8 timer_num, uint16 value) { timer->CNT = value; } +// Returns the current timer counter value. Probably very inaccurate if the +// counter is running with a low prescaler. uint16 timer_get_count(uint8 timer_num) { Timer *timer; ASSERT(timer_num > 0 && timer_num <= 4); @@ -193,6 +199,7 @@ uint16 timer_get_count(uint8 timer_num) { return timer->CNT; } +// Does what it says void timer_set_prescaler(uint8 timer_num, uint16 prescale) { Timer *timer; ASSERT(timer_num > 0 && timer_num <= 4); @@ -214,6 +221,8 @@ void timer_set_prescaler(uint8 timer_num, uint16 prescale) { timer->PSC = prescale; } +// This sets the "reload" or "overflow" value for the entire timer. We should +// probably settle on either "reload" or "overflow" to prevent confusion? void timer_set_reload(uint8 timer_num, uint16 max_reload) { Timer *timer; ASSERT(timer_num > 0 && timer_num <= 4); @@ -235,15 +244,28 @@ void timer_set_reload(uint8 timer_num, uint16 max_reload) { timer->ARR = max_reload; } - +// This quickly disables all 4 timers, presumably as part of a system shutdown +// or similar to prevent interrupts and PWM output without 16 seperate function +// calls to timer_set_mode void timer_disable_all(void) { // Note: this must be very robust because it gets called from, eg, ASSERT // TODO: rewrite? - Timer *timer; Timer *timers[4] = { (Timer*)TIMER1_BASE, - (Timer*)TIMER2_BASE, (Timer*)TIMER3_BASE, (Timer*)TIMER4_BASE, }; int i; - for (i = 0; i < 4; i++) { timer = timers[i]; timer->CR1 = 0; timer->CCER = - 0; } } + Timer *timer; + Timer *timers[4] = { (Timer*)TIMER1_BASE, + (Timer*)TIMER2_BASE, + (Timer*)TIMER3_BASE, + (Timer*)TIMER4_BASE, + }; + int i; + + for (i = 0; i < 4; i++) { + timer = timers[i]; + timer->CR1 = 0; + timer->CCER = 0; + } +} +// Sets the mode of individual timer channels, including a DISABLE mode void timer_set_mode(uint8 timer_num, uint8 channel, uint8 mode) { Timer *timer; switch (timer_num) { @@ -359,6 +381,7 @@ void timer_set_mode(uint8 timer_num, uint8 channel, uint8 mode) { } } +// This sets the compare value (aka the trigger) for a given timer channel void timer_set_compare_value(uint8 timer_num, uint8 compare_num, uint16 value) { // The faster version of this function is the inline timer_pwm_write_ccr @@ -395,6 +418,8 @@ void timer_set_compare_value(uint8 timer_num, uint8 compare_num, uint16 value) { } } +// Stores a pointer to the passed usercode interrupt function and configures +// the actual ISR so that it will actually be called void timer_attach_interrupt(uint8 timer_num, uint8 compare_num, voidFuncPtr handler) { Timer *timer; ASSERT(timer_num > 0 && timer_num <= 4 && compare_num > 0 && compare_num <= 4); @@ -455,12 +480,20 @@ void timer_detach_interrupt(uint8 timer_num, uint8 compare_num) { } } +// The following are the actual interrupt handlers; 1 for each timer which must +// determine which actual compare value (aka channel) was triggered. +// +// These ISRs get called when the timer interrupt is enabled, the timer is running, and +// the timer count equals any of the CCR registers /or/ has overflowed. +// +// This is a rather long implementation... void TIM1_CC_IRQHandler(void) { - // This is a rather long implementation... Timer *timer = (Timer*)TIMER1_BASE; uint16 sr_buffer; sr_buffer = timer->SR; + // Simply switch/case-ing here doesn't work because multiple + // CC flags may be high. if(sr_buffer & 0x10){ // CC4 flag timer->SR &= ~(0x10); if(timer1_handlers[3]) { -- cgit v1.2.3