diff --git a/examples/stm32/f4/stm32f4-discovery/timer/Makefile b/examples/stm32/f4/stm32f4-discovery/timer/Makefile new file mode 100644 index 0000000..1e790ae --- /dev/null +++ b/examples/stm32/f4/stm32f4-discovery/timer/Makefile @@ -0,0 +1,25 @@ +## +## This file is part of the libopencm3 project. +## +## Copyright (C) 2009 Uwe Hermann +## +## 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 . +## + +BINARY = timer + +LDSCRIPT = ../stm32f4-discovery.ld + +include ../../Makefile.include + diff --git a/examples/stm32/f4/stm32f4-discovery/timer/README.md b/examples/stm32/f4/stm32f4-discovery/timer/README.md new file mode 100644 index 0000000..55e1006 --- /dev/null +++ b/examples/stm32/f4/stm32f4-discovery/timer/README.md @@ -0,0 +1,15 @@ +# README + +This example demonstrates the use of timers to trigger an interrupt. This +example will toggle two LEDs spelling out the following morse code: + +SOS -> ...---... + +Where dots are .1s, dashes .2s, gaps .05s and the word pause .5s. + +It's intended for the ST STM32F4DISCOVERY eval board. It should blink +the LEDs on the board. + +## Board connections + +*none required* diff --git a/examples/stm32/f4/stm32f4-discovery/timer/timer.c b/examples/stm32/f4/stm32f4-discovery/timer/timer.c new file mode 100644 index 0000000..f67262d --- /dev/null +++ b/examples/stm32/f4/stm32f4-discovery/timer/timer.c @@ -0,0 +1,190 @@ +/* + * This file is part of the libopencm3 project. + * + * Copyright (C) 2015 Piotr Esden-Tempski + * Copyright (C) 2015 Jack Ziesing + * + * 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 . + */ + +#include +#include +#include +#include +#include + +uint16_t frequency_sequence[18] = { + 1000, + 500, + 1000, + 500, + 1000, + 500, + 2000, + 500, + 2000, + 500, + 2000, + 500, + 1000, + 500, + 1000, + 500, + 1000, + 5000, +}; + +uint16_t frequency_sel = 0; + +uint16_t compare_time; +uint16_t new_time; +uint16_t frequency; +int debug = 0; + +static void clock_setup(void) +{ + rcc_clock_setup_hse_3v3(&hse_8mhz_3v3[CLOCK_3V3_168MHZ]); +} + +static void gpio_setup(void) +{ + /* Enable GPIOC clock. */ + rcc_periph_clock_enable(RCC_GPIOD); + + /* Set GPIO12 (in GPIO port C) to 'output push-pull'. */ + gpio_mode_setup(GPIOD, GPIO_MODE_OUTPUT, + GPIO_PUPD_NONE, GPIO12 | GPIO13); + + gpio_set(GPIOD, GPIO12); + gpio_clear(GPIOD, GPIO13); +} + +static void tim_setup(void) +{ + /* Enable TIM2 clock. */ + rcc_periph_clock_enable(RCC_TIM2); + + /* Enable TIM2 interrupt. */ + nvic_enable_irq(NVIC_TIM2_IRQ); + + /* Reset TIM2 peripheral. */ + timer_reset(TIM2); + + /* Timer global mode: + * - No divider + * - Alignment edge + * - Direction up + */ + timer_set_mode(TIM2, TIM_CR1_CKD_CK_INT, + TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); + + /* Reset prescaler value. + * Running the clock at 5kHz. + */ + /* + * On STM32F4 the timers are not running directly from pure APB1 or + * APB2 clock busses. The APB1 and APB2 clocks used for timers might + * be the double of the APB1 and APB2 clocks. This depends on the + * setting in DCKCFGR register. By default the behaviour is the + * following: If the Prescaler APBx is greater than 1 the derived timer + * APBx clocks will be double of the original APBx frequencies. Only if + * the APBx prescaler is set to 1 the derived timer APBx will equal the + * original APBx frequencies. + * + * In our case here the APB1 is devided by 4 system frequency and APB2 + * divided by 2. This means APB1 timer will be 2 x APB1 and APB2 will + * be 2 x APB2. So when we try to calculate the prescaler value we have + * to use rcc_apb1_freqency * 2!!! + * + * For additional information see reference manual for the stm32f4 + * familiy of chips. Page 204 and 213 + */ + timer_set_prescaler(TIM2, ((rcc_apb1_frequency * 2) / 10000)); + + /* Enable preload. */ + timer_disable_preload(TIM2); + + /* Continous mode. */ + timer_continuous_mode(TIM2); + + /* Period (36kHz). */ + timer_set_period(TIM2, 65535); + + /* Disable outputs. */ + timer_disable_oc_output(TIM2, TIM_OC1); + timer_disable_oc_output(TIM2, TIM_OC2); + timer_disable_oc_output(TIM2, TIM_OC3); + timer_disable_oc_output(TIM2, TIM_OC4); + + /* -- OC1 configuration -- */ + + /* Configure global mode of line 1. */ + timer_disable_oc_clear(TIM2, TIM_OC1); + timer_disable_oc_preload(TIM2, TIM_OC1); + timer_set_oc_slow_mode(TIM2, TIM_OC1); + timer_set_oc_mode(TIM2, TIM_OC1, TIM_OCM_FROZEN); + + /* Set the capture compare value for OC1. */ + timer_set_oc_value(TIM2, TIM_OC1, 1000); + + /* ---- */ + + /* ARR reload enable. */ + timer_disable_preload(TIM2); + + /* Counter enable. */ + timer_enable_counter(TIM2); + + /* Enable commutation interrupt. */ + timer_enable_irq(TIM2, TIM_DIER_CC1IE); +} + +void tim2_isr(void) +{ + if (timer_get_flag(TIM2, TIM_SR_CC1IF)) { + + /* Clear compare interrupt flag. */ + timer_clear_flag(TIM2, TIM_SR_CC1IF); + + /* + * Get current timer value to calculate next + * compare register value. + */ + compare_time = timer_get_counter(TIM2); + + /* Calculate and set the next compare value. */ + frequency = frequency_sequence[frequency_sel++]; + new_time = compare_time + frequency; + + timer_set_oc_value(TIM2, TIM_OC1, new_time); + if (frequency_sel == 18) + frequency_sel = 0; + + /* Toggle LED to indicate compare event. */ + gpio_toggle(GPIOD, GPIO12); + gpio_toggle(GPIOD, GPIO13); + } +} + +int main(void) +{ + clock_setup(); + gpio_setup(); + tim_setup(); + + while (1) + __asm("nop"); + + return 0; +}