cfec3c6e2d
Mainly for PWM use for now. With example to set the LED to different brightness via COAP. We switch the LED with 50 kHz (20µs) in this example.
143 lines
4.3 KiB
C
143 lines
4.3 KiB
C
/*
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* Copyright (c) 2014, Ralf Schlatterbeck Open Source Consulting
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*/
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/**
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* \addgroup hardware timer
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*
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* @{
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*/
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/**
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* \file
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* Alternative initialisation with period in microseconds
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* \author
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* Ralf Schlatterbeck <rsc@runtux.com>
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*/
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#include <avr/pgmspace.h>
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#include "contiki.h"
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#include "rtimer-arch.h"
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#include "hw_timer.h"
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/* one for each possible timer */
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uint16_t hwt_max_ticks [6];
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#define PERIOD_MAX (0xFFFFFFFF / (F_CPU / 1000000))
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/* for 16-bit timer: */
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#define TICKS_MAX 0xFFFF
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#define TICKS_MIN 0xFF
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int8_t
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hwtimer_pwm_ini (uint8_t timer, uint32_t period_us, uint8_t pwm_type, uint8_t ocra)
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{
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uint32_t ticks = 0;
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uint8_t clock = HWT_CLOCK_PRESCALER_1024;
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uint8_t wgm = HWT_WGM_NORMAL;
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HWT_CHECK_TIMER (timer);
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if (period_us > PERIOD_MAX) {
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period_us = PERIOD_MAX;
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}
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ticks = (F_CPU / 1000000) * period_us;
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/* Non-fast PWM modes have half the frequency */
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if (pwm_type != HWT_PWM_FAST) {
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ticks >>= 1;
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}
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/*
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* Divisors are 1, 8, 64, 256, 1024, shifts between these are
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* 3, 3, 2, 2, respectively. We modify `ticks` in place, the AVR can
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* shift only one bit in one instruction, so shifting isn't cheap.
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* We try to get the *maximum* prescaler that still permits a tick
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* resolution of at least 8 bit.
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*/
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if (ticks <= (TICKS_MIN << 3)) {
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clock = HWT_CLOCK_PRESCALER_1;
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}
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else if ((ticks >>= 3) <= (TICKS_MIN << 3)) {
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clock = HWT_CLOCK_PRESCALER_8;
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}
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else if ((ticks >>= 3) <= (TICKS_MIN << 2)) {
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clock = HWT_CLOCK_PRESCALER_64;
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}
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else if ((ticks >>= 2) <= (TICKS_MIN << 2)) {
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clock = HWT_CLOCK_PRESCALER_256;
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}
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else if ((ticks >>= 2) > TICKS_MAX) {
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ticks = TICKS_MAX;
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}
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hwt_max_ticks [timer] = ticks;
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switch (pwm_type) {
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case HWT_PWM_FAST:
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wgm = ocra ? HWT_WGM_PWM_FAST_OCRA : HWT_WGM_PWM_FAST_ICR;
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break;
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case HWT_PWM_PHASE_CORRECT:
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wgm = ocra ? HWT_WGM_PWM_PHASE_OCRA : HWT_WGM_PWM_PHASE_ICR;
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break;
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case HWT_PWM_PHASE_FRQ_CORRECT:
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default:
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wgm = ocra ? HWT_WGM_PWM_PHASE_FRQ_OCRA : HWT_WGM_PWM_PHASE_FRQ_ICR;
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break;
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}
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/* Special 8- 9- 10-bit modes */
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if (pwm_type == HWT_PWM_FAST || pwm_type == HWT_PWM_PHASE_CORRECT) {
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if (ticks == 0xFF) {
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wgm = (pwm_type == HWT_PWM_FAST)
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? HWT_WGM_PWM_FAST_8_BIT
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: HWT_WGM_PWM_PHASE_8_BIT;
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}
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else if (ticks == 0x1FF) {
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wgm = (pwm_type == HWT_PWM_FAST)
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? HWT_WGM_PWM_FAST_9_BIT
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: HWT_WGM_PWM_PHASE_9_BIT;
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}
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else if (ticks == 0x3FF) {
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wgm = (pwm_type == HWT_PWM_FAST)
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? HWT_WGM_PWM_FAST_10_BIT
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: HWT_WGM_PWM_PHASE_10_BIT;
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}
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}
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return hwtimer_ini (timer, wgm, clock, ticks);
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}
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uint32_t hwtimer_pwm_max_ticks (uint8_t timer)
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{
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if (timer > 5) {
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return 0;
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}
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return hwt_max_ticks [timer];
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}
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/*
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* ex:ts=8:et:sw=2
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*/
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/** @} */
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