Introduce firmware directory

1 files changed, 143 insertions, 0 deletions

diff --git a/firmware/src/main.c b/firmware/src/main.c
new file mode 100644
index 0000000..8e39278
--- /dev/null
+++ b/firmware/src/main.c
@@ -0,0 +1,143 @@
+// vim: shiftwidth=4 tabstop=4 noexpandtab
+
+
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/timer.h>
+#include <libopencm3/cm3/nvic.h>
+
+
+static void clock_init(void);
+static void gpio_init(void);
+static void nvic_init(void);
+static void timer_init(void);
+
+void tim2_isr(void);
+
+
+void main(void)
+{
+	clock_init();
+	gpio_init();
+	gpio_clear(GPIOC, GPIO13);  // set onboard LED on
+	nvic_init();
+	timer_init();
+
+	while(1);  // wait forever
+}
+
+
+static void clock_init(void)
+{
+	// set sysclk to 72 MHz via external 8 MHz crystal
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+
+	// enable clocks for GPIO ports B and C
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	
+	// enable clock for timer 2 (blinking)
+	rcc_periph_clock_enable(RCC_TIM2);
+
+	// enable clock for timer 3 (PWM)
+	rcc_periph_clock_enable(RCC_TIM3);
+
+	// enable clock for alternate functions
+	rcc_periph_clock_enable(RCC_AFIO);  // TODO is this necessary?
+}
+
+
+static void gpio_init(void)
+{
+	// init PC13 onboard LED for blinking
+	gpio_set_mode(
+		GPIOC,
+		GPIO_MODE_OUTPUT_50_MHZ,
+		GPIO_CNF_OUTPUT_PUSHPULL,
+		GPIO13
+	);
+	
+	// setup PB0 (connected to TIM3_CH3) for PWM
+	gpio_set_mode(
+		GPIOB,
+		GPIO_MODE_OUTPUT_50_MHZ,
+		GPIO_CNF_OUTPUT_ALTFN_PUSHPULL,
+		GPIO_TIM3_CH3
+	);
+}
+
+
+static void nvic_init(void)
+{
+	// enable timer 2 interrupt and set priority
+	nvic_enable_irq(NVIC_TIM2_IRQ);
+	nvic_set_priority(NVIC_TIM2_IRQ, 1);
+}
+
+
+static void timer_init(void)
+{
+	// setup timer 2 for blinking
+	timer_set_counter(TIM2, 1);
+	timer_set_prescaler(TIM2, 1440);
+	timer_set_period(TIM2, 50);
+
+	// enable timer / counter 2 and the corresponding interrupt for blinking
+	timer_enable_irq(TIM2, TIM_DIER_UIE);
+	timer_enable_counter(TIM2);
+
+	/* 
+		enable timer / counter 3
+	*/
+
+	/* Clock division and mode */
+	TIM3_CR1 = TIM_CR1_CKD_CK_INT | TIM_CR1_CMS_EDGE;
+	/* Period */
+	TIM3_ARR = 65535;
+	/* Prescaler */
+	TIM3_PSC = 0;
+	TIM3_EGR = TIM_EGR_UG;
+
+	/* ---- */
+	/* Output compare 3 mode and preload */
+	TIM3_CCMR2 |= TIM_CCMR2_OC3M_PWM1 | TIM_CCMR2_OC3PE;
+
+	/* Polarity and state */
+	TIM3_CCER |= TIM_CCER_CC3P | TIM_CCER_CC3E;
+	//TIM3_CCER |= TIM_CCER_CC3E;
+
+	/* Capture compare value */
+	TIM3_CCR3 = 30000;
+
+	/* ---- */
+	/* ARR reload enable */
+	TIM3_CR1 |= TIM_CR1_ARPE;
+
+	/* Counter enable */
+	TIM3_CR1 |= TIM_CR1_CEN;
+}
+
+
+void tim2_isr(void)
+{
+	// PWM handling
+	static uint32_t pwm_value;
+	if (pwm_value == 0) {
+		pwm_value = 65535;
+	}
+	else {
+		pwm_value -= 20;
+	}
+	TIM3_CCR3 = pwm_value;
+
+	// toggle blink LED
+	static uint32_t counter;
+	counter += 1;
+	if (counter > 500) {
+		gpio_toggle(GPIOC, GPIO13);
+		counter = 0;
+	}
+
+	// clear interrrupt flag
+	TIM_SR(TIM2) &= ~TIM_SR_UIF;
+}