timer.c
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/*
* Copyright (C) 2015 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup cpu_msp430fxyz
* @{
*
* @file
* @brief Low-level timer driver implementation
*
* This implementation does only support one fixed timer, as defined in the
* boards periph_conf.h file.
*
* @todo Generalize to handle more timers and make them configurable
* through the board's `periph_conf.h`
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*
* @}
*/
#include "cpu.h"
#include "periph_cpu.h"
#include "periph_conf.h"
#include "periph/timer.h"
/**
* @brief Save reference to the timer callback
*/
static timer_cb_t isr_cb;
/**
* @brief Save argument for the ISR callback
*/
static void *isr_arg;
int timer_init(tim_t dev, unsigned long freq, timer_cb_t cb, void *arg)
{
/* using fixed TIMER_BASE for now */
if (dev != 0) {
return -1;
}
/* TODO: configure time-base depending on freq value */
if (freq != 1000000ul) {
return -1;
}
/* reset the timer A configuration */
TIMER_BASE->CTL = TIMER_CTL_CLR;
/* save callback */
isr_cb = cb;
isr_arg = arg;
/* configure timer to use the SMCLK with prescaler of 8 */
TIMER_BASE->CTL = (TIMER_CTL_TASSEL_SMCLK | TIMER_CTL_ID_DIV8);
/* configure CC channels */
for (int i = 0; i < TIMER_CHAN; i++) {
TIMER_BASE->CCTL[i] = 0;
}
/* start the timer in continuous mode */
TIMER_BASE->CTL |= TIMER_CTL_MC_CONT;
return 0;
}
int timer_set(tim_t dev, int channel, unsigned int timeout)
{
uint16_t target = TIMER_BASE->R + (uint16_t)timeout;
return timer_set_absolute(dev, channel, (unsigned int)target);
}
int timer_set_absolute(tim_t dev, int channel, unsigned int value)
{
if (dev != 0 || channel > TIMER_CHAN) {
return -1;
}
TIMER_BASE->CCR[channel] = value;
TIMER_BASE->CCTL[channel] &= ~(TIMER_CCTL_CCIFG);
TIMER_BASE->CCTL[channel] |= (TIMER_CCTL_CCIE);
return 0;
}
int timer_clear(tim_t dev, int channel)
{
if (dev != 0 || channel > TIMER_CHAN) {
return -1;
}
TIMER_BASE->CCTL[channel] &= ~(TIMER_CCTL_CCIE);
return 0;
}
unsigned int timer_read(tim_t dev)
{
return (unsigned int)TIMER_BASE->R;
}
void timer_start(tim_t dev)
{
TIMER_BASE->CTL |= TIMER_CTL_MC_CONT;
}
void timer_stop(tim_t dev)
{
TIMER_BASE->CTL &= ~(TIMER_CTL_MC_MASK);
}
void timer_irq_enable(tim_t dev)
{
/* TODO: not supported, yet
*
* Problem here: there is no means, of globally disabling timer interrupts.
* We could just enable the interrupts for all CC channels, but this would
* mean, that we might enable interrupts for channels, that are not active.
* I guess we need to remember the interrupt state of all channels before
* disabling and then restore this state when enabling again?! */
}
void timer_irq_disable(tim_t dev)
{
/* TODO: not supported, yet */
}
ISR(TIMER_ISR_CC0, isr_timer_a_cc0)
{
__enter_isr();
TIMER_BASE->CCTL[0] &= ~(TIMER_CCTL_CCIE);
isr_cb(isr_arg, 0);
__exit_isr();
}
ISR(TIMER_ISR_CCX, isr_timer_a_ccx)
{
__enter_isr();
int chan = (int)(TIMER_IVEC->TAIV >> 1);
TIMER_BASE->CCTL[chan] &= ~(TIMER_CCTL_CCIE);
isr_cb(isr_arg, chan);
__exit_isr();
}