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trezor-firmware/legacy/timer.c

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/*
* This file is part of the Trezor project, https://trezor.io/
*
* Copyright (C) 2016 Saleem Rashid <trezor@saleemrashid.com>
*
* This library is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library. If not, see <http://www.gnu.org/licenses/>.
*/
#include "timer.h"
#include <libopencm3/cm3/systick.h>
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#include <libopencm3/cm3/vector.h>
#include <libopencm3/stm32/rcc.h>
/* 1 tick = 1 ms */
extern volatile uint32_t system_millis;
/*
* Initialise the Cortex-M3 SysTick timer
*/
void timer_init(void) {
system_millis = 0;
/*
* MCU clock (120 MHz) as source
*
* (120 MHz / 8) = 15 clock pulses
*
*/
systick_set_clocksource(STK_CSR_CLKSOURCE_AHB_DIV8);
STK_CVR = 0;
/*
* 1 tick = 1 ms @ 120 MHz
*
* (15 clock pulses * 1000 ms) = 15000 clock pulses
*
* Send an interrupt every (N - 1) clock pulses
*/
systick_set_reload(14999);
/* SysTick as interrupt */
systick_interrupt_enable();
systick_counter_enable();
}
void sys_tick_handler(void) { system_millis++; }