mirror of https://github.com/ArduPilot/ardupilot
108 lines
2.9 KiB
C++
108 lines
2.9 KiB
C++
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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#include "AP_TimerProcess.h"
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extern "C" {
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#include <inttypes.h>
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#include <stdint.h>
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#include "WConstants.h"
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#include <avr/interrupt.h>
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}
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uint8_t AP_TimerProcess::_period;
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ap_procedure AP_TimerProcess::_proc[AP_TIMERPROCESS_MAX_PROCS];
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ap_procedure AP_TimerProcess::_failsafe;
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bool AP_TimerProcess::_in_timer_call;
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uint8_t AP_TimerProcess::_pidx = 0;
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AP_TimerProcess::AP_TimerProcess(uint8_t period)
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{
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_period = period;
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}
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void AP_TimerProcess::init( Arduino_Mega_ISR_Registry * isr_reg )
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{
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// Enable Timer2 Overflow interrupt to trigger process.
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TIMSK2 = 0; // Disable interrupts
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TCCR2A = 0; // normal counting mode
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TCCR2B = _BV(CS21) | _BV(CS22); // Set prescaler of clk/256
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TCNT2 = 0; // Set count to zero, so it goes off right away.
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TIFR2 = _BV(TOV2); // clear pending interrupts;
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TIMSK2 = _BV(TOIE2); // enable the overflow interrupt
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_failsafe = NULL;
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_in_timer_call = false;
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for (uint8_t i = 0; i < AP_TIMERPROCESS_MAX_PROCS; i++)
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_proc[i] = NULL;
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isr_reg->register_signal( ISR_REGISTRY_TIMER2_OVF, AP_TimerProcess::run);
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}
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/*
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register a process to be called at the timer interrupt rate
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*/
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void AP_TimerProcess::register_process(ap_procedure proc)
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{
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// see if its already registered (due to double initialisation
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// of a driver)
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for (uint8_t i=0; i<_pidx; i++) {
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if (_proc[i] == proc) return;
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}
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cli();
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if (_pidx < AP_TIMERPROCESS_MAX_PROCS)
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_proc[_pidx++] = proc;
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sei();
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}
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void AP_TimerProcess::set_failsafe(ap_procedure proc)
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{
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_failsafe = proc;
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}
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void AP_TimerProcess::run(void)
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{
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// we enable the interrupt again immediately and also enable
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// interrupts. This allows other time critical interrupts to
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// run (such as the serial receive interrupt). We catch the
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// timer calls taking too long using _in_timer_call.
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// This approach also gives us a nice uniform spacing between
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// timer calls
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TCNT2 = _period;
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sei();
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uint32_t tnow = micros();
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if (_in_timer_call) {
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// the timer calls took longer than the period of the
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// timer. This is bad, and may indicate a serious
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// driver failure. We can't just call the drivers
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// again, as we could run out of stack. So we only
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// call the _failsafe call. It's job is to detect if
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// the drivers or the main loop are indeed dead and to
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// activate whatever failsafe it thinks may help if
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// need be. We assume the failsafe code can't
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// block. If it does then we will recurse and die when
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// we run out of stack
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if (_failsafe != NULL) {
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_failsafe(tnow);
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}
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return;
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}
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_in_timer_call = true;
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// now call the timer based drivers
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for (int i = 0; i < _pidx; i++) {
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if (_proc[i] != NULL) {
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_proc[i](tnow);
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}
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}
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// and the failsafe, if one is setup
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if (_failsafe != NULL) {
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_failsafe(tnow);
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}
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_in_timer_call = false;
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}
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