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AP_HAL_AVR: move scheduler's timer-hw dependent methods to a separate cpp

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This commit is contained in:
Pat Hickey 2012-12-06 15:24:55 -08:00 committed by Andrew Tridgell
parent d9f69923f2
commit f9e9b8a7ef
4 changed files with 189 additions and 162 deletions
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1
libraries/AP_HAL_AVR/AP_HAL_AVR_Namespace.h
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@ -26,6 +26,7 @@ namespace AP_HAL_AVR {
class APM1RCOutput;
class APM2RCOutput;
class AVRScheduler;
class AVRTimer;
class AVRSemaphore;
class ISRRegistry;
}

172
libraries/AP_HAL_AVR/Scheduler.cpp
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@ -1,4 +1,3 @@
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
#include <avr/io.h>
#include <avr/interrupt.h>
@ -7,20 +6,15 @@
#include "Scheduler.h"
using namespace AP_HAL_AVR;
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
extern const AP_HAL::HAL& hal;
static volatile uint32_t timer0_overflow_count = 0;
static volatile uint32_t timer0_millis = 0;
static uint8_t timer0_fract = 0;
/* AVRScheduler timer interrupt period is controlled by TCNT2.
* 256-62 gives a 1kHz period. */
#define RESET_TCNT2_VALUE (256 - 62)
/* Static AVRScheduler variables: */
AVRTimer AVRScheduler::_timer;
AP_HAL::TimedProc AVRScheduler::_failsafe = NULL;
volatile bool AVRScheduler::_timer_suspended = false;
AP_HAL::TimedProc AVRScheduler::_timer_proc[AVR_SCHEDULER_MAX_TIMER_PROCS] = {NULL};
@ -38,57 +32,9 @@ AVRScheduler::AVRScheduler() :
void AVRScheduler::init(void* _isrregistry) {
ISRRegistry* isrregistry = (ISRRegistry*) _isrregistry;
// this needs to be called before setup() or some functions won't
// work there
sei();
// set timer 0 prescale factor to 64
// this combination is for the standard 168/328/1280/2560
sbi(TCCR0B, CS01);
sbi(TCCR0B, CS00);
// enable timer 0 overflow interrupt
sbi(TIMSK0, TOIE0);
// timers 1 and 2 are used for phase-correct hardware pwm
// this is better for motors as it ensures an even waveform
// note, however, that fast pwm mode can achieve a frequency of up
// 8 MHz (with a 16 MHz clock) at 50% duty cycle
TCCR1B = 0;
// set timer 1 prescale factor to 64
sbi(TCCR1B, CS11);
sbi(TCCR1B, CS10);
// put timer 1 in 8-bit phase correct pwm mode
sbi(TCCR1A, WGM10);
sbi(TCCR3B, CS31); // set timer 3 prescale factor to 64
sbi(TCCR3B, CS30);
sbi(TCCR3A, WGM30); // put timer 3 in 8-bit phase correct pwm mode
sbi(TCCR4B, CS41); // set timer 4 prescale factor to 64
sbi(TCCR4B, CS40);
sbi(TCCR4A, WGM40); // put timer 4 in 8-bit phase correct pwm mode
sbi(TCCR5B, CS51); // set timer 5 prescale factor to 64
sbi(TCCR5B, CS50);
sbi(TCCR5A, WGM50); // put timer 5 in 8-bit phase correct pwm mode
// set a2d prescale factor to 128
// 16 MHz / 128 = 125 KHz, inside the desired 50-200 KHz range.
// XXX: this will not work properly for other clock speeds, and
// this code should use F_CPU to determine the prescale factor.
sbi(ADCSRA, ADPS2);
sbi(ADCSRA, ADPS1);
sbi(ADCSRA, ADPS0);
// enable a2d conversions
sbi(ADCSRA, ADEN);
// the bootloader connects pins 0 and 1 to the USART; disconnect them
// here so they can be used as normal digital i/o; they will be
// reconnected in Serial.begin()
UCSR0B = 0;
/* _timer: sets up timer hardware to Arduino defaults, and
* uses TIMER0 to implement millis & micros */
_timer.init();
/* TIMER2: Setup the overflow interrupt to occur at 1khz. */
TIMSK2 = 0; /* Disable timer interrupt */
@ -101,88 +47,24 @@ void AVRScheduler::init(void* _isrregistry) {
isrregistry->register_signal(ISR_REGISTRY_TIMER2_OVF, _timer_event);
}
#define clockCyclesPerMicrosecond() ( F_CPU / 1000000L )
#define clockCyclesToMicroseconds(a) ( ((a) * 1000L) / (F_CPU / 1000L) )
// the prescaler is set so that timer0 ticks every 64 clock cycles, and the
// the overflow handler is called every 256 ticks.
#define MICROSECONDS_PER_TIMER0_OVERFLOW (clockCyclesToMicroseconds(64 * 256))
// the whole number of milliseconds per timer0 overflow
#define MILLIS_INC (MICROSECONDS_PER_TIMER0_OVERFLOW / 1000)
// the fractional number of milliseconds per timer0 overflow. we shift right
// by three to fit these numbers into a byte. (for the clock speeds we care
// about - 8 and 16 MHz - this doesn't lose precision.)
#define FRACT_INC ((MICROSECONDS_PER_TIMER0_OVERFLOW % 1000) >> 3)
#define FRACT_MAX (1000 >> 3)
SIGNAL(TIMER0_OVF_vect)
{
// copy these to local variables so they can be stored in registers
// (volatile variables must be read from memory on every access)
uint32_t m = timer0_millis;
uint8_t f = timer0_fract;
m += MILLIS_INC;
f += FRACT_INC;
if (f >= FRACT_MAX) {
f -= FRACT_MAX;
m += 1;
}
timer0_fract = f;
timer0_millis = m;
timer0_overflow_count++;
}
uint32_t AVRScheduler::millis()
{
uint32_t m;
uint8_t oldSREG = SREG;
// disable interrupts while we read timer0_millis or we might get an
// inconsistent value (e.g. in the middle of a write to timer0_millis)
cli();
m = timer0_millis;
SREG = oldSREG;
return m;
}
/* micros() is essentially a static method, but we need it to be available
* via virtual dispatch through the hal. */
uint32_t AVRScheduler::micros() {
return _micros();
return _timer.micros();
}
/* _micros() is the implementation of micros() as a static private method
* so we can use it from inside _timer_event() without virtual dispatch. */
uint32_t AVRScheduler::_micros() {
uint32_t m;
uint8_t t;
uint8_t oldSREG = SREG;
cli();
uint32_t AVRScheduler::millis() {
return _timer.millis();
}
m = timer0_overflow_count;
t = TCNT0;
if ((TIFR0 & _BV(TOV0)) && (t < 255))
m++;
SREG = oldSREG;
return ((m << 8) + t) * (64 / clockCyclesPerMicrosecond());
void AVRScheduler::delay_microseconds(uint16_t us) {
_timer.delay_microseconds(us);
}
void AVRScheduler::delay(uint32_t ms)
{
uint32_t start = _micros();
uint32_t start = _timer.micros();
while (ms > 0) {
while ((micros() - start) >= 1000) {
while ((_timer.micros() - start) >= 1000) {
ms--;
if (ms == 0) break;
start += 1000;
@ -195,30 +77,6 @@ void AVRScheduler::delay(uint32_t ms)
}
}
/* Delay for the given number of microseconds. Assumes a 16 MHz clock. */
void AVRScheduler::delay_microseconds(uint16_t us)
{
// for the 16 MHz clock on most Arduino boards
// for a one-microsecond delay, simply return. the overhead
// of the function call yields a delay of approximately 1 1/8 us.
if (--us == 0)
return;
// the following loop takes a quarter of a microsecond (4 cycles)
// per iteration, so execute it four times for each microsecond of
// delay requested.
us <<= 2;
// account for the time taken in the preceeding commands.
us -= 2;
// busy wait
__asm__ __volatile__ (
"1: sbiw %0,1" "\n\t" // 2 cycles
"brne 1b" : "=w" (us) : "0" (us) // 2 cycles
);
}
void AVRScheduler::register_delay_callback(AP_HAL::Proc proc,
uint16_t min_time_ms) {
_delay_cb = proc;
@ -252,7 +110,7 @@ bool AVRScheduler::defer_timer_process(AP_HAL::TimedProc proc) {
} else {
_timer_suspended = true;
sei();
proc(micros());
proc(_timer.micros());
_timer_suspended = false;
return true;
}
@ -283,7 +141,7 @@ void AVRScheduler::_timer_event() {
TCNT2 = RESET_TCNT2_VALUE;
sei();
uint32_t tnow = _micros();
uint32_t tnow = _timer.micros();
if (_in_timer_proc) {
// the timer calls took longer than the period of the
// timer. This is bad, and may indicate a serious

17
libraries/AP_HAL_AVR/Scheduler.h
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@ -7,6 +7,16 @@
#define AVR_SCHEDULER_MAX_TIMER_PROCS 4
/* Class for managing the AVR Timers: */
class AP_HAL_AVR::AVRTimer {
public:
static void init();
static uint32_t millis();
static uint32_t micros();
static void delay_microseconds(uint16_t us);
};
/* Scheduler implementation: */
class AP_HAL_AVR::AVRScheduler : public AP_HAL::Scheduler {
public:
AVRScheduler();
@ -30,16 +40,13 @@ public:
void reboot();
private:
/* Implementation specific methods: */
static AVRTimer _timer;
/* timer_event() is static so it can be called from an interrupt.
* (This is effectively a singleton class.)
* _prefix: this method must be public */
static void _timer_event();
/* _micros() is the implementation of micros() as a static private method
* so we can use it from inside _timer_event() without virtual dispatch. */
static uint32_t _micros();
AP_HAL::Proc _delay_cb;
uint16_t _min_delay_cb_ms;
static AP_HAL::TimedProc _failsafe;

161
libraries/AP_HAL_AVR/Scheduler_Timer.cpp Normal file
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@ -0,0 +1,161 @@
#include <avr/io.h>
#include <avr/interrupt.h>
#include "HAL_AVR.h"
#include "Scheduler.h"
using namespace AP_HAL_AVR;
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
static volatile uint32_t timer0_overflow_count = 0;
static volatile uint32_t timer0_millis = 0;
static uint8_t timer0_fract = 0;
void AVRTimer::init() {
// this needs to be called before setup() or some functions won't
// work there
sei();
// set timer 0 prescale factor to 64
// this combination is for the standard 168/328/1280/2560
sbi(TCCR0B, CS01);
sbi(TCCR0B, CS00);
// enable timer 0 overflow interrupt
sbi(TIMSK0, TOIE0);
// timers 1 and 2 are used for phase-correct hardware pwm
// this is better for motors as it ensures an even waveform
// note, however, that fast pwm mode can achieve a frequency of up
// 8 MHz (with a 16 MHz clock) at 50% duty cycle
TCCR1B = 0;
// set timer 1 prescale factor to 64
sbi(TCCR1B, CS11);
sbi(TCCR1B, CS10);
// put timer 1 in 8-bit phase correct pwm mode
sbi(TCCR1A, WGM10);
sbi(TCCR3B, CS31); // set timer 3 prescale factor to 64
sbi(TCCR3B, CS30);
sbi(TCCR3A, WGM30); // put timer 3 in 8-bit phase correct pwm mode
sbi(TCCR4B, CS41); // set timer 4 prescale factor to 64
sbi(TCCR4B, CS40);
sbi(TCCR4A, WGM40); // put timer 4 in 8-bit phase correct pwm mode
sbi(TCCR5B, CS51); // set timer 5 prescale factor to 64
sbi(TCCR5B, CS50);
sbi(TCCR5A, WGM50); // put timer 5 in 8-bit phase correct pwm mode
// set a2d prescale factor to 128
// 16 MHz / 128 = 125 KHz, inside the desired 50-200 KHz range.
// XXX: this will not work properly for other clock speeds, and
// this code should use F_CPU to determine the prescale factor.
sbi(ADCSRA, ADPS2);
sbi(ADCSRA, ADPS1);
sbi(ADCSRA, ADPS0);
// enable a2d conversions
sbi(ADCSRA, ADEN);
// the bootloader connects pins 0 and 1 to the USART; disconnect them
// here so they can be used as normal digital i/o; they will be
// reconnected in Serial.begin()
UCSR0B = 0;
}
#define clockCyclesPerMicrosecond() ( F_CPU / 1000000L )
#define clockCyclesToMicroseconds(a) ( ((a) * 1000L) / (F_CPU / 1000L) )
// the prescaler is set so that timer0 ticks every 64 clock cycles, and the
// the overflow handler is called every 256 ticks.
#define MICROSECONDS_PER_TIMER0_OVERFLOW (clockCyclesToMicroseconds(64 * 256))
// the whole number of milliseconds per timer0 overflow
#define MILLIS_INC (MICROSECONDS_PER_TIMER0_OVERFLOW / 1000)
// the fractional number of milliseconds per timer0 overflow. we shift right
// by three to fit these numbers into a byte. (for the clock speeds we care
// about - 8 and 16 MHz - this doesn't lose precision.)
#define FRACT_INC ((MICROSECONDS_PER_TIMER0_OVERFLOW % 1000) >> 3)
#define FRACT_MAX (1000 >> 3)
SIGNAL(TIMER0_OVF_vect)
{
// copy these to local variables so they can be stored in registers
// (volatile variables must be read from memory on every access)
uint32_t m = timer0_millis;
uint8_t f = timer0_fract;
m += MILLIS_INC;
f += FRACT_INC;
if (f >= FRACT_MAX) {
f -= FRACT_MAX;
m += 1;
}
timer0_fract = f;
timer0_millis = m;
timer0_overflow_count++;
}
uint32_t AVRTimer::millis()
{
uint32_t m;
uint8_t oldSREG = SREG;
// disable interrupts while we read timer0_millis or we might get an
// inconsistent value (e.g. in the middle of a write to timer0_millis)
cli();
m = timer0_millis;
SREG = oldSREG;
return m;
}
uint32_t AVRTimer::micros() {
uint32_t m;
uint8_t t;
uint8_t oldSREG = SREG;
cli();
m = timer0_overflow_count;
t = TCNT0;
if ((TIFR0 & _BV(TOV0)) && (t < 255))
m++;
SREG = oldSREG;
return ((m << 8) + t) * (64 / clockCyclesPerMicrosecond());
}
/* Delay for the given number of microseconds. Assumes a 16 MHz clock. */
void AVRTimer::delay_microseconds(uint16_t us)
{
// for the 16 MHz clock on most Arduino boards
// for a one-microsecond delay, simply return. the overhead
// of the function call yields a delay of approximately 1 1/8 us.
if (--us == 0)
return;
// the following loop takes a quarter of a microsecond (4 cycles)
// per iteration, so execute it four times for each microsecond of
// delay requested.
us <<= 2;
// account for the time taken in the preceeding commands.
us -= 2;
// busy wait
__asm__ __volatile__ (
"1: sbiw %0,1" "\n\t" // 2 cycles
"brne 1b" : "=w" (us) : "0" (us) // 2 cycles
);
}