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osd-contiki/cpu/avr/hw_timer.h
Ralf Schlatterbeck 6c06f43417 Minor optimisations of timer init
2014-06-29 17:12:13 +02:00

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/*
* Copyright (c) 2014, Ralf Schlatterbeck Open Source Consulting
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*/
/**
* \defgroup hardware timer
*
* This module wraps hardware timers of AVR microcontrollers.
* Currently we only support 16-bit timers. The main focus is currently
* on PWM generation. But input capture and interrupt routines are on
* the TODO list, see below. We currently support the AVR ATmega128RFA1
* so this should be generalized to supported timers of other AVR
* microcontrollers.
*
* Datasheet references in the following refer to ATmega128RFA1 data sheet
*
* TODO: Allow input capture.
* TODO: Allow definition of interrupt routine; check if merkur board
* supports necessary pins.
* TODO: Generalize for 8-bit timers.
* TODO: Check other AVR microcontrollers and the supported timers.
*
* @{
*/
/**
* \file
* Header file for hardware timer of AVR microcontrollers
* \author
* Ralf Schlatterbeck <rsc@runtux.com>
*
*/
#ifndef hw_timer_h
#define hw_timer_h
#include "contiki.h"
#include "rtimer-arch.h"
#ifndef PLAT_TIMER
#define PLAT_TIMER -1
#endif
/*
* All routines return a negative number for error and 0 for success.
* The negative return value indicates the error.
*/
#define HWT_ERR_INVALID_TIMER (-1)
#define HWT_ERR_INVALID_WGM (-2)
#define HWT_ERR_INVALID_COM (-3)
#define HWT_ERR_INVALID_CLOCK (-4)
#define HWT_ERR_INVALID_CHANNEL (-5)
/*
* Timer waveform generation modes (WGM), see data sheet
* chapter 18 "16-bit Timer/Counter (Timer/Counter 1,3,4, and 5)
* 18.9 "Modes of Operation", in particular Table 18-5
*/
#define HWT_WGM_NORMAL 0
#define HWT_WGM_PWM_PHASE_8_BIT 1
#define HWT_WGM_PWM_PHASE_9_BIT 2
#define HWT_WGM_PWM_PHASE_10_BIT 3
#define HWT_WGM_CTC_OCRA 4
#define HWT_WGM_PWM_FAST_8_BIT 5
#define HWT_WGM_PWM_FAST_9_BIT 6
#define HWT_WGM_PWM_FAST_10_BIT 7
#define HWT_WGM_PWM_PHASE_FRQ_ICR 8
#define HWT_WGM_PWM_PHASE_FRQ_OCRA 9
#define HWT_WGM_PWM_PHASE_ICR 10
#define HWT_WGM_PWM_PHASE_OCRA 11
#define HWT_WGM_CTC_ICR 12
#define HWT_WGM_RESERVED 13
#define HWT_WGM_PWM_FAST_ICR 14
#define HWT_WGM_PWM_FAST_OCRA 15
#define HWT_WGM_MASK 15
#define HWT_WGM_MASK_LOW 3
#define HWT_WGM_MASK_HIGH (HWT_WGM_MASK - HWT_WGM_MASK_LOW)
#define HWT_WGM_SHIFT_LOW 0
#define HWT_WGM_SHIFT_HIGH 1
/*
* Timer compare output modes (COM),
* chapter 18 "16-bit Timer/Counter (Timer/Counter 1,3,4, and 5)
* 18.8 "Compare Match Output Unit", in particular Tables 18-2,3,4
*/
#define HWT_COM_NORMAL 0
#define HWT_COM_TOGGLE 1
#define HWT_COM_CLEAR 2
#define HWT_COM_SET 3
#define HWT_COM_MASK 3
/*
* Clock select, clock can be off, use prescaler or external clock
* source on Tn pin. See Table 18-11 (for Timer 1 but this is the same
* for all the timers).
*/
#define HWT_CLOCK_OFF 0
#define HWT_CLOCK_PRESCALER_1 1
#define HWT_CLOCK_PRESCALER_8 2
#define HWT_CLOCK_PRESCALER_64 3
#define HWT_CLOCK_PRESCALER_256 4
#define HWT_CLOCK_PRESCALER_1024 5
#define HWT_CLOCK_EXTERN_FALLING 6
#define HWT_CLOCK_EXTERN_RISING 7
#define HWT_CLOCK_MASK 7
/*
* Timer channels A B C
*/
#define HWT_CHANNEL_A 0
#define HWT_CHANNEL_B 1
#define HWT_CHANNEL_C 2
#define HWT_CHANNEL_D 3
#define HWT_CHANNEL_MASK 3
/* The following macros are defined for timer values 1,3,4,5 */
#define HWT_ICR(t) \
((t)<4?((t)==1?(&ICR1) :(&ICR3)) :((t)==4?(&ICR4) :(&ICR5)))
#define HWT_OCRA(t) \
((t)<4?((t)==1?(&OCR1A):(&OCR3A)):((t)==4?(&OCR4A):(&OCR5A)))
#define HWT_OCRB(t) \
((t)<4?((t)==1?(&OCR1B):(&OCR3B)):((t)==4?(&OCR4B):(&OCR5B)))
#define HWT_OCRC(t) \
((t)<4?((t)==1?(&OCR1C):(&OCR3C)):((t)==4?(&OCR4C):(&OCR5C)))
#define HWT_OCR(t,c) \
( (c)==HWT_CHANNEL_A \
? (HWT_OCRA(t)) \
: ((c)==HWT_CHANNEL_B?HWT_OCRB(t):HWT_OCRC(t)) \
)
#define HWT_TCCRA(t) \
( (t)<4 \
? ((t)==1?(&TCCR1A):(&TCCR3A)) \
: ((t)==4?(&TCCR4A):(&TCCR5A)) \
)
#define HWT_TCCRB(t) \
( (t)<4 \
? ((t)==1?(&TCCR1B):(&TCCR3B)) \
: ((t)==4?(&TCCR4B):(&TCCR5B)) \
)
#define HWT_TCCRC(t) \
( (t)<4 \
? ((t)==1?(&TCCR1C):(&TCCR3C)) \
: ((t)==4?(&TCCR4C):(&TCCR5C)) \
)
#define HWT_TCNT(t) \
( (t)<4 \
? ((t)==1?(&TCNT1) :(&TCNT3)) \
: ((t)==4?(&TCNT4) :(&TCNT5)) \
)
#define HWT_CLR_COM(timer, channel) \
(*HWT_TCCRA (timer) &= ~(HWT_COM_MASK << (6 - 2 * (channel))))
#define HWT_SET_COM(timer, channel, com) \
( HWT_CLR_COM (timer, channel) \
, (*HWT_TCCRA (timer) |= ((com) << (6 - 2 * (channel)))) \
)
#define HWT_CHECK_TIMER(timer) \
do { \
if ((timer) == 0 || (timer) == 2 || (timer) == PLAT_TIMER || (timer) > 5) {\
return HWT_ERR_INVALID_TIMER; \
} \
} while (0)
#define HWT_CHECK_CHANNEL(chan) \
do { \
if ((chan) > HWT_CHANNEL_C) { \
return HWT_ERR_INVALID_CHANNEL; \
} \
} while (0)
#define HWT_PWM_FAST 0
#define HWT_PWM_PHASE_CORRECT 1
#define HWT_PWM_PHASE_FRQ_CORRECT 2
/**
* \brief Initialize the hardware timer with the given settings
* \param timer: Timer to use
* \param wgm: waveform generation mode to use, see definitions
* \param clock: Prescaler or external clock settings
* \param maxt: Maximum counter value, not used for fixed modes, this
* sets ICRn for the ICR modes and OCRnA for the OCR modes
* \return see HWT_ERR definitions for return codes, returns 0 if ok
*
* The initial compare output mode is set to HWT_COM_NORMAL (off) for
* all outputs (pwm disabled).
*
* Note that this sets the compare output mode COM registers to 0,
* turning off PWM on outputs.
*/
static inline int8_t
hwtimer_ini (uint8_t timer, uint8_t wgm, uint8_t clock, uint16_t maxt)
{
int8_t i;
HWT_CHECK_TIMER (timer);
if (wgm > HWT_WGM_MASK || wgm == HWT_WGM_RESERVED) {
return HWT_ERR_INVALID_WGM;
}
if (clock > HWT_CLOCK_MASK) {
return HWT_ERR_INVALID_CLOCK;
}
/* Turn off clock, no need to disable interrupt */
*HWT_TCCRB (timer) &= ~HWT_CLOCK_MASK;
*HWT_TCCRA (timer) &= ~(HWT_WGM_MASK_LOW << HWT_WGM_SHIFT_LOW);
*HWT_TCCRA (timer) |= ((wgm & HWT_WGM_MASK_LOW) << HWT_WGM_SHIFT_LOW);
*HWT_TCCRB (timer) &= ~(HWT_WGM_MASK_HIGH << HWT_WGM_SHIFT_HIGH);
*HWT_TCCRB (timer) |= ((wgm & HWT_WGM_MASK_HIGH) << HWT_WGM_SHIFT_HIGH);
for (i=0; i<3; i++) {
HWT_CLR_COM (timer, i);
}
if ( wgm == HWT_WGM_PWM_PHASE_FRQ_ICR
|| wgm == HWT_WGM_PWM_PHASE_ICR
|| wgm == HWT_WGM_CTC_ICR
|| wgm == HWT_WGM_PWM_FAST_ICR
)
{
*HWT_ICR (timer) = maxt;
}
if ( wgm == HWT_WGM_CTC_OCRA
|| wgm == HWT_WGM_PWM_PHASE_FRQ_OCRA
|| wgm == HWT_WGM_PWM_PHASE_OCRA
|| wgm == HWT_WGM_PWM_FAST_OCRA
)
{
*HWT_OCRA (timer) = maxt;
}
/* Set clock, finally */
*HWT_TCCRB (timer) |= clock;
return 0;
}
/* Needed for implementation */
#define HWT_PERIOD_MAX_ (0xFFFFFFFF / (F_CPU / 1000000))
/* for 16-bit timer: */
#define HWT_TICKS_MAX_ 0xFFFF
#define HWT_TICKS_MIN_ 0xFF
/**
* \brief Convenience function to initialize hardware timer for PWM
* \param timer: Timer to use
* \param pwm_type: See HWT_PWM* macros
* \param period_us: Period of the timer in µs
* \param ocra: Use OCRnA register if set, ICRn otherwise
* \return see HWT_ERR definitions for return codes, returns 0 if ok
*
* This function can be called instead of hwtimer_ini and sets up the
* timer for one of the PWM modes. There are fast, phase-correct and
* phase- and frequency correct modes, refer to the datasheet for
* semantics.
*
* The function tries to initialize the timer to a mode that doesn't use
* one of the internal registers OCRnA or ICRn for specifying the upper
* bound of the counter. For fast PWM and phase-correct PWM there are
* fixed 8-, 9-, and 10-bit modes that can be used if the computed value
* fits one of these setups.
*
* We try to get the *maximum* prescaler that still permits a tick
* resolution of at least 8 bit. This will not work for very high
* frequencies.
*
* If the specified period is too large to fit into a 16-bit timer we
* take the maximum period that is still possible, this may be
* substatially higher than specified.
*
* Note that when using OCRnA for the upper bound of the counter, the
* pin associated with this register can not be used for PWM. Instead it
* can be used to change the period.
*/
static inline int8_t
hwtimer_pwm_ini (uint8_t timer, uint32_t period_us, uint8_t pwm_type, uint8_t ocra)
{
uint32_t ticks = 0;
uint8_t clock = HWT_CLOCK_PRESCALER_1024;
uint8_t wgm = HWT_WGM_NORMAL;
HWT_CHECK_TIMER (timer);
if (period_us > HWT_PERIOD_MAX_) {
period_us = HWT_PERIOD_MAX_;
}
ticks = (F_CPU / 1000000) * period_us;
/* Non-fast PWM modes have half the frequency */
if (pwm_type != HWT_PWM_FAST) {
ticks >>= 1;
}
/*
* Divisors are 1, 8, 64, 256, 1024, shifts between these are
* 3, 3, 2, 2, respectively. We modify `ticks` in place, the AVR can
* shift only one bit in one instruction, so shifting isn't cheap.
* We try to get the *maximum* prescaler that still permits a tick
* resolution of at least 8 bit.
*/
if (ticks <= (HWT_TICKS_MIN_ << 3)) {
clock = HWT_CLOCK_PRESCALER_1;
}
else if ((ticks >>= 3) <= (HWT_TICKS_MIN_ << 3)) {
clock = HWT_CLOCK_PRESCALER_8;
}
else if ((ticks >>= 3) <= (HWT_TICKS_MIN_ << 2)) {
clock = HWT_CLOCK_PRESCALER_64;
}
else if ((ticks >>= 2) <= (HWT_TICKS_MIN_ << 2)) {
clock = HWT_CLOCK_PRESCALER_256;
}
else if ((ticks >>= 2) > HWT_TICKS_MAX_) {
ticks = HWT_TICKS_MAX_;
}
switch (pwm_type) {
case HWT_PWM_FAST:
wgm = ocra ? HWT_WGM_PWM_FAST_OCRA : HWT_WGM_PWM_FAST_ICR;
break;
case HWT_PWM_PHASE_CORRECT:
wgm = ocra ? HWT_WGM_PWM_PHASE_OCRA : HWT_WGM_PWM_PHASE_ICR;
break;
case HWT_PWM_PHASE_FRQ_CORRECT:
default:
wgm = ocra ? HWT_WGM_PWM_PHASE_FRQ_OCRA : HWT_WGM_PWM_PHASE_FRQ_ICR;
break;
}
/* Special 8- 9- 10-bit modes */
if (pwm_type == HWT_PWM_FAST || pwm_type == HWT_PWM_PHASE_CORRECT) {
if (ticks == 0xFF) {
wgm = (pwm_type == HWT_PWM_FAST)
? HWT_WGM_PWM_FAST_8_BIT
: HWT_WGM_PWM_PHASE_8_BIT;
}
else if (ticks == 0x1FF) {
wgm = (pwm_type == HWT_PWM_FAST)
? HWT_WGM_PWM_FAST_9_BIT
: HWT_WGM_PWM_PHASE_9_BIT;
}
else if (ticks == 0x3FF) {
wgm = (pwm_type == HWT_PWM_FAST)
? HWT_WGM_PWM_FAST_10_BIT
: HWT_WGM_PWM_PHASE_10_BIT;
}
}
return hwtimer_ini (timer, wgm, clock, ticks);
}
/*
* Simple init macro for sane default values
*/
#define hwtimer_pwm_ini_simple (timer, period_us) \
hwtimer_pwm_ini ((timer), HWT_PWM_PHASE_CORRECT, (period_us), 0)
/**
* \brief Maximum timer value usable in hwtimer_set_pwm
* \param timer: Timer to use
* \return max. timer value according to current timer setup
* negative value if wrong timer given
* a positive value is guaranteed to fit into 16 bit unsigned.
*/
static inline int32_t hwtimer_pwm_max_ticks (uint8_t timer)
{
uint8_t wgm = 0;
HWT_CHECK_TIMER (timer);
wgm = ((*HWT_TCCRA (timer) >> HWT_WGM_SHIFT_LOW) & HWT_WGM_MASK_LOW)
| ((*HWT_TCCRB (timer) >> HWT_WGM_SHIFT_HIGH) & HWT_WGM_MASK_HIGH)
;
switch (wgm) {
case HWT_WGM_PWM_PHASE_8_BIT:
case HWT_WGM_PWM_FAST_8_BIT:
return 0xFF;
case HWT_WGM_PWM_PHASE_9_BIT:
case HWT_WGM_PWM_FAST_9_BIT:
return 0x1FF;
case HWT_WGM_PWM_PHASE_10_BIT:
case HWT_WGM_PWM_FAST_10_BIT:
return 0x3FF;
case HWT_WGM_CTC_OCRA:
case HWT_WGM_PWM_PHASE_FRQ_OCRA:
case HWT_WGM_PWM_PHASE_OCRA:
case HWT_WGM_PWM_FAST_OCRA:
return *HWT_OCRA (timer);
case HWT_WGM_PWM_PHASE_FRQ_ICR:
case HWT_WGM_PWM_PHASE_ICR:
case HWT_WGM_CTC_ICR:
case HWT_WGM_PWM_FAST_ICR:
return *HWT_ICR (timer);
case HWT_WGM_NORMAL:
return 0xFFFF;
}
return HWT_ERR_INVALID_WGM;
}
/*
* The following functions are defined inline to allow for compiler
* optimizations if some of the parameters are constant.
*/
/**
* \brief Set PWM duty cycle
* \param timer: Timer to use
* \param channel: Channel to use, see HWT_CHANNEL definitions
* \param pwm: Duty cycle
* \return see HWT_ERR definitions for return codes, returns 0 if ok
*
* Note that the available range for the duty cycle depends on the timer
* setup and the chosen mode.
*/
static inline int8_t
hwtimer_set_pwm (uint8_t timer, uint8_t channel, uint16_t pwm)
{
uint8_t sreg = 0;
HWT_CHECK_TIMER (timer);
HWT_CHECK_CHANNEL (channel);
sreg = SREG;
cli ();
*HWT_OCR (timer, channel) = pwm;
SREG = sreg;
return 0;
}
/**
* \brief Set compare output mode
* \param timer: Timer to use
* \param channel: Channel to use, see HWT_CHANNEL definitions
* \param com: compare output mode for given channel
* \return see HWT_ERR definitions for return codes, returns 0 if ok
*/
static inline int8_t
hwtimer_set_com (uint8_t timer, uint8_t channel, uint8_t com)
{
HWT_CHECK_TIMER (timer);
HWT_CHECK_CHANNEL (channel);
if (com > HWT_COM_MASK) {
return HWT_ERR_INVALID_COM;
}
if (com) {
HWT_SET_COM (timer, channel, com);
} else {
HWT_CLR_COM (timer, channel);
}
return 0;
}
/**
* \brief Convenience function for setting compare output mode for PWM
* \param timer: Timer to use
* \param channel: Channel to use, see HWT_CHANNEL definitions
* \return see HWT_ERR definitions for return codes, returns 0 if ok
*/
static inline int8_t
hwtimer_pwm_enable (uint8_t timer, uint8_t channel)
{
return hwtimer_set_com (timer, channel, HWT_COM_CLEAR);
}
/**
* \brief Convenience function for inverse compare output mode for PWM
* \param timer: Timer to use
* \param channel: Channel to use, see HWT_CHANNEL definitions
* \return see HWT_ERR definitions for return codes, returns 0 if ok
*/
static inline int8_t
hwtimer_pwm_inverse (uint8_t timer, uint8_t channel)
{
return hwtimer_set_com (timer, channel, HWT_COM_SET);
}
/**
* \brief Convenience function for setting compare output mode to off
* \param timer: Timer to use
* \param channel: Channel to use, see HWT_CHANNEL definitions
* \return see HWT_ERR definitions for return codes, returns 0 if ok
*/
static inline int8_t
hwtimer_pwm_disable (uint8_t timer, uint8_t channel)
{
return hwtimer_set_com (timer, channel, HWT_COM_NORMAL);
}
/**
* \brief Turn off the clock
* \param timer: Timer to use
* \return see HWT_ERR definitions for return codes, returns 0 if ok
*/
static inline int8_t
hwtimer_fin (uint8_t timer)
{
HWT_CHECK_TIMER (timer);
*HWT_TCCRB (timer) &= ~HWT_CLOCK_MASK;
*HWT_TCCRB (timer) |= HWT_CLOCK_OFF; /* technically not necessary this is 0 */
return 0;
}
#endif /* hw_timer_h */
/*
* ex:ts=8:et:sw=2
*/
/** @} */
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