/* * This file is part of the libopenstm32 project. * * Copyright (C) 2010 Thomas Otto * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program 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 General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see . */ #include #include #include #include #include #include /* Set STM32 to 72 MHz. HSE 16MHz */ void clock_setup(void) { /* enable Internal High Speed Oscillator */ rcc_osc_on(HSI); rcc_wait_for_osc_ready(HSI); /* Select HSI as SYSCLK source. */ rcc_set_sysclk_source(SW_SYSCLKSEL_HSICLK); /* enable External High Speed Oscillator 16MHz */ rcc_osc_on(HSE); rcc_wait_for_osc_ready(HSE); rcc_set_sysclk_source(SW_SYSCLKSEL_HSECLK); /* set prescalers for ADC, ABP1, ABP2... make this before touching the PLL */ rcc_set_hpre(HPRE_SYSCLK_NODIV); //prescales the AHB clock from the SYSCLK rcc_set_adcpre(ADCPRE_PLCK2_DIV6); //prescales the ADC from the APB2 clock; max 14MHz rcc_set_ppre1(PPRE1_HCLK_DIV2); //prescales the APB1 from the AHB clock; max 36MHz rcc_set_ppre2(PPRE2_HCLK_NODIV); //prescales the APB2 from the AHB clock; max 72MHz /* sysclk should run with 72MHz -> 2 Waitstates ; choose 0WS from 0-24MHz, 1WS from 24-48MHz, 2WS from 48-72MHz */ flash_set_ws(FLASH_LATENCY_2WS); /* Set the PLL multiplication factor to 9. -> 16MHz (external) * 9 (multiplier) / 2 (PLLXTPRE_HSE_CLK_DIV2) = 72MHz */ rcc_set_pll_multiplication_factor(PLLMUL_PLL_CLK_MUL9); /* Select HSI as PLL source. */ rcc_set_pll_source(PLLSRC_HSE_CLK); /* divide external frequency by 2 before entering pll (only valid/needed for HSE) */ rcc_set_pllxtpre(PLLXTPRE_HSE_CLK_DIV2); /* Enable PLL oscillator and wait for it to stabilize. */ rcc_osc_on(PLL); rcc_wait_for_osc_ready(PLL); /* Select PLL as SYSCLK source. */ rcc_set_sysclk_source(SW_SYSCLKSEL_PLLCLK); } void gpio_setup(void) { /* Enable GPIOB clock. */ rcc_peripheral_enable_clock(&RCC_APB2ENR, IOPBEN); /* Set GPIO6/7 (in GPIO port B) to 'output push-pull' for the LEDs. */ gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO6); gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO7); } void nvic_setup() { /* without this the timer interrupt routine will never be called */ nvic_enable_irq(NVIC_TIM2_IRQ); nvic_set_priority(NVIC_TIM2_IRQ, 1); } void tim2_isr() { /* LED2 on/off */ gpio_toggle(GPIOB, GPIO6); /* clear interrrupt flag */ TIM_SR(TIM2) &= ~TIM_SR_UIF; } int main(void) { clock_setup(); gpio_setup(); nvic_setup(); gpio_clear(GPIOB, GPIO7); /* LED1 on */ gpio_set(GPIOB, GPIO6); /* LED2 off */ rcc_peripheral_enable_clock(&RCC_APB1ENR, TIM2EN); /* the goal is to let the LED2 glow for a second and then be off for a second */ /* Set timer start value */ TIM_CNT(TIM2) = 1; /* Set timer prescaler. 72MHz/1440 => 50000 counts per second */ TIM_PSC(TIM2) = 1440; /* End timer value. If this value is reached an interrupt is generated */ TIM_ARR(TIM2) = 50000; /* Update interrupt enable */ TIM_DIER(TIM2) |= TIM_DIER_UIE; /* Start timer */ TIM_CR1(TIM2) |= TIM_CR1_CEN; while(1); /* Halt. */ return 0; }