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// lpc176x timer interrupt scheduling
//
// Copyright (C) 2018 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "LPC17xx.h" // LPC_TIM0
#include "board/irq.h" // irq_disable
#include "board/misc.h" // timer_read_time
#include "board/timer_irq.h" // timer_dispatch_many
#include "internal.h" // enable_pclock
#include "sched.h" // DECL_INIT
// Set the next irq time
static void
timer_set(uint32_t value)
{
LPC_TIM0->MR0 = value;
LPC_TIM0->IR = 0x01;
}
// Return the current time (in absolute clock ticks).
uint32_t
timer_read_time(void)
{
return LPC_TIM0->TC;
}
// Activate timer dispatch as soon as possible
void
timer_kick(void)
{
timer_set(timer_read_time() + 50);
}
void
timer_init(void)
{
// Disable timer
LPC_TIM0->TCR = 0x02;
// Setup clock and prescaler (divide sys clock by 4)
enable_pclock(PCLK_TIMER0);
LPC_TIM0->PR = 3;
// Enable interrupts
NVIC_SetPriority(TIMER0_IRQn, 2);
NVIC_EnableIRQ(TIMER0_IRQn);
LPC_TIM0->MCR = 0x01;
// Clear counter value
LPC_TIM0->TC = 0;
timer_kick();
// Start timer
LPC_TIM0->TCR = 0x01;
}
DECL_INIT(timer_init);
void __visible __aligned(16) // aligning helps stabilize perf benchmarks
TIMER0_IRQHandler(void)
{
irq_disable();
uint32_t next = timer_dispatch_many();
timer_set(next);
irq_enable();
}
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