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#ifdef __cplusplus
extern "C" {
#endif
#include "stm32f091xc.h"
// GPIO A
#define PINOUT_DISP_CLK (5)
#define PINOUT_DISP_DIO (6)
#define PINOUT_POT (7)
// GPIO B
#define PINOUT_LED_1 (3)
#define PINOUT_LED_2 (5)
#define PINOUT_LED_3 (4)
#define PINOUT_LED_4 (6)
const unsigned short leds[] = {PINOUT_LED_1, PINOUT_LED_2, PINOUT_LED_3, PINOUT_LED_4};
#define PINOUT_BTN (8)
volatile bool led_direction = false;
/*
* This function configures the I/O-ports that are used by the I/O-shield. It
* uses register RCC_AHBENR to enable the clocks for the ports that are used,
* register GPIOx_MODER to configure pins as input, analog or output and
* GPIOx_PUPDR to configure pull-up and pull-down resistors.
*/
void shield_config() {
// enable internal clocks
RCC->AHBENR |= RCC_AHBENR_GPIOAEN | RCC_AHBENR_GPIOBEN; // GPIO A and B
RCC->APB2ENR |= RCC_APB2ENR_ADC1EN; // ADC1 peripheral
RCC->APB1ENR |= RCC_APB1ENR_TIM3EN; // TIM3
// clear mode register configuration bits
GPIOB->MODER &= ~((0b11 << (PINOUT_LED_1 * 2)) |
(0b11 << (PINOUT_LED_2 * 2)) |
(0b11 << (PINOUT_LED_3 * 2)) |
(0b11 << (PINOUT_LED_4 * 2)) |
(0b11 << (PINOUT_BTN * 2)));
GPIOA->MODER &= ~((0b11 << (PINOUT_DISP_CLK * 2)) |
(0b11 << (PINOUT_DISP_DIO * 2)) |
(0b11 << (PINOUT_POT * 2)));
// set output mode register configuration bits
// 0b00 -> input mode (reset state)
// 0b01 -> general purpose output mode
// 0b10 -> alternate function mode
// 0b11 -> analog mode
GPIOB->MODER |= (0b01 << (PINOUT_LED_1 * 2)) |
(0b01 << (PINOUT_LED_2 * 2)) |
(0b01 << (PINOUT_LED_3 * 2)) |
(0b01 << (PINOUT_LED_4 * 2)) |
(0b00 << (PINOUT_BTN * 2));
GPIOA->MODER |= (0b01 << (PINOUT_DISP_CLK * 2)) |
(0b01 << (PINOUT_DISP_DIO * 2)) |
(0b11 << (PINOUT_POT * 2));
// pull-up resistor for button
GPIOB->PUPDR &= ~(0b11 << (PINOUT_BTN * 2));
GPIOB->PUPDR |= (0b01 << (PINOUT_BTN * 2));
// calirate ADC1
ADC1->CR |= ADC_CR_ADCAL;
while (ADC1->CR & ADC_CR_ADCAL);
ADC1->CR |= ADC_CR_ADEN; // enable ADC1
// TIM3 setup
TIM3->PSC = 8000 - 1; // prescaler set so each timer tick is 1ms
TIM3->CCMR1 |= TIM_CCMR1_OC1M_0;
TIM3->EGR |= TIM_EGR_UG; // generate update event
TIM3->CR1 |= TIM_CR1_CEN; // enable counter
}
void toggle_direction() {
led_direction = !led_direction;
}
void EXTI4_15_IRQHandler(void) {
// toggle_direction();
led_direction = !led_direction;
return;
}
void interrupt_setup() {
RCC->APB2ENR |= RCC_APB2ENR_SYSCFGEN;
// RCC->APB2ENR |= RCC_APB2ENR_SYSCFGCOMPEN;
SYSCFG->EXTICR[PINOUT_BTN / 4] &= ~(0xF << ((PINOUT_BTN % 4) * 4));
SYSCFG->EXTICR[PINOUT_BTN / 4] |= (0x1 << ((PINOUT_BTN % 4) * 4));
EXTI->IMR |= (1 << PINOUT_BTN);
EXTI->RTSR &= ~(1 << PINOUT_BTN);
EXTI->FTSR |= (1 << PINOUT_BTN);
NVIC_SetPriority(EXTI4_15_IRQn, 3);
NVIC_EnableIRQ(EXTI4_15_IRQn);
}
/*
* This function drives led <num> of the I/O-shield. <num> should be the number
* of the LED to drive (0, 1, 2 or 3) and <on> should be an integer with value
* 0 or 1 which indicates if the LED should be turned on (1) or off (0).
*/
void led_write(int num, int on) {
GPIOB->ODR &= ~(1 << leds[num]);
GPIOB->ODR |= (on << leds[num]);
}
/*
* This function returns the status of the pushbutton of the I/O-shield.
* Return value 1 indicates that the button is currently pressed and return
* value 0 indicates that the button is currently not pressed.
*/
int button_read() {
return (GPIOB->IDR & (1 << PINOUT_BTN)) == 0;
}
/*
* Read potmeter value as analog value between 0 and 2^12 - 1
*/
unsigned int pot_read() {
ADC1->CHSELR = (1 << PINOUT_POT);
ADC1->CR |= ADC_CR_ADSTART;
while (ADC1->CR & ADC_CR_ADSTART);
uint16_t result = ADC1->DR;
ADC1->CR |= ADC_CR_ADSTP;
return result;
}
void next_led() {
static uint8_t led = 0;
for(int j = 0; j < 4; j++) led_write(j, 0); // clear all leds
led = (led + led_direction * 2 - 1) & 0b11; // calculate next led index
led_write(led, 1);
}
void dumb_delay() {
for(unsigned long i = 0; i < 50e3; i++);
}
/**
* This function uses timer 3 to generate a blocking delay of <milliseconds>.
* It uses the channel 1 capture/compare register to check if the time (in
* milliseconds) has expired.
*/
int timer_delay(unsigned short millis) {
TIM3->CCR1 = millis; // set delay amount
TIM3->CNT = 0; // reset timer
TIM3->SR &= ~(TIM_SR_CC1IF); // reset capture/compare output
while ((TIM3->SR & TIM_SR_CC1IF) == 0); // wait until c/c goes high
}
int main() {
shield_config();
interrupt_setup();
while (1) {
// if ((TIM3->SR & TIM_SR_CC1IF) > 0) {
// toggle_direction();
// TIM3->CNT = 0;
// TIM3->SR &= ~(TIM_SR_CC1IF);
// TIM3->EGR |= TIM_EGR_UG;
// }
timer_delay(100);
next_led();
}
}
#ifdef __cplusplus
}
#endif
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