Example programs

src/blink/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=blink
+OBJS=blink.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/blink/blink.c

@@ -0,0 +1,23 @@
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOC);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	for (;;) {
+		gpio_clear(GPIOC, GPIO13);
+
+		for (int i=0; i<1000000; i++)
+			asm volatile ("");
+
+		gpio_set(GPIOC, GPIO13);
+
+		for (int i=0; i<2000000; i++)
+			asm volatile ("");
+	}
+}

src/blink2/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=blink
+OBJS=blink.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/blink2/blink.c

@@ -0,0 +1,33 @@
+#include <libopencm3/cm3/systick.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+
+static void delay_ms(unsigned int ms)
+{
+	systick_clear();
+	for (unsigned int i=0; i<ms; i++)
+		while (!systick_get_countflag())
+			;
+}
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOC);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
+	systick_set_reload(71999);
+	systick_counter_enable();
+
+	for (;;) {
+		gpio_clear(GPIOC, GPIO13);
+		delay_ms(100);
+		gpio_set(GPIOC, GPIO13);
+		delay_ms(500);
+	}
+
+	return 0;
+}

src/blink3/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=blink
+OBJS=blink.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/blink3/blink.c

@@ -0,0 +1,53 @@
+#include <libopencm3/cm3/systick.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+
+static void delay_ms(unsigned int ms)
+{
+	systick_clear();
+	for (unsigned int i=0; i<ms; i++)
+		while (!systick_get_countflag())
+			;
+}
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_GPIOC);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	// PA0 ... PA2 = LEDs
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO0);
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO1);
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO2);
+	gpio_clear(GPIOA, GPIO0);
+	gpio_clear(GPIOA, GPIO1);
+	gpio_clear(GPIOA, GPIO2);
+
+	systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
+	systick_set_reload(71999);
+	systick_counter_enable();
+
+	for (;;) {
+		gpio_set(GPIOA, GPIO0);
+		delay_ms(100);
+		gpio_clear(GPIOA, GPIO0);
+
+		gpio_set(GPIOA, GPIO1);
+		delay_ms(100);
+		gpio_clear(GPIOA, GPIO1);
+
+		gpio_set(GPIOA, GPIO2);
+		delay_ms(100);
+		gpio_clear(GPIOA, GPIO2);
+
+		gpio_clear(GPIOC, GPIO13);
+		delay_ms(100);
+		gpio_set(GPIOC, GPIO13);
+	}
+
+	return 0;
+}

src/button/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=button
+OBJS=button.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/button/button.c

@@ -0,0 +1,30 @@
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_GPIOC);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	// PA0 ... PA2 = LEDs
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO0);
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO1);
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO2);
+
+	// PA3 = button (pull-up)
+	gpio_set_mode(GPIOA, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, GPIO3);
+	gpio_set(GPIOA, GPIO3);
+
+	for (;;) {
+		if (gpio_get(GPIOA, GPIO3))
+			gpio_set(GPIOA, GPIO0 | GPIO1 | GPIO2);
+		else
+			gpio_clear(GPIOA, GPIO0 | GPIO1 | GPIO2);
+	}
+
+	return 0;
+}

src/example.mk

@@ -0,0 +1,8 @@
+STM32LIB=$(ROOT)/../ucw-stm32lib
+OPENCM3_DIR=$(ROOT)/../libopencm3
+
+WITH_BOOT_LOADER=1
+WITH_DFU_FLASH=1
+DFU_ARGS=-d 4242:0008
+
+include $(STM32LIB)/mk/bluepill.mk

src/matrix/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=matrix
+OBJS=matrix.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/matrix/matrix.c

@@ -0,0 +1,167 @@
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+
+#include <string.h>
+
+typedef unsigned char byte;
+
+static void wait(void)
+{
+	for (int i=0; i<7200; i++)
+		asm volatile ("");
+}
+
+static void set_reg(int reg, int data)
+{
+	data |= reg << 8;
+
+	gpio_clear(GPIOB, GPIO13);
+	wait();
+
+	for (int mask=0x8000; mask; mask >>= 1) {
+		if (data & mask)
+			gpio_set(GPIOB, GPIO12);
+		else
+			gpio_clear(GPIOB, GPIO12);
+		wait();
+		gpio_set(GPIOB, GPIO14);
+		wait();
+		gpio_clear(GPIOB, GPIO14);
+		wait();
+	}
+
+	gpio_set(GPIOB, GPIO13);
+	wait();
+}
+
+byte display[8];
+
+#if 0
+static unsigned char smile[8] = {
+	0x66,	/* .##..##. */
+	0x66,	/* .##..##. */
+	0x00,	/* ........ */
+	0x18,	/* ...##... */
+	0x00,	/* ........ */
+	0xc3,	/* ##....## */
+	0x66,	/* .##..##. */
+	0x3c,	/* ..####.. */
+};
+#endif
+
+static void refresh_display(void)
+{
+	for (int i=1; i<=8; i++)
+		set_reg(i, display[8-i]);
+}
+
+static signed char dirs[4][2] = {{1,0}, {0,-1}, {-1,0}, {0,1}};
+
+static byte snake_dir;
+#define SNAKE_MAX 65
+static byte snake[SNAKE_MAX][2];
+static byte snake_tail, snake_head;
+static byte food[2];
+static unsigned int rng_state = 0xdeadbeef;
+
+static byte buttons[2];
+
+static void gen_food(void)
+{
+	food[0] = (rng_state >> 28) & 7;
+	food[1] = (rng_state >> 20) & 7;
+	rng_state *= 0x3771cadb;
+}
+
+static void snake_init(void)
+{
+	snake[0][0] = 0;
+	snake[0][1] = 0;
+	snake_dir = 3;
+	snake_tail = 0;
+	snake_head = 1;
+	gen_food();
+}
+
+static void snake_show(void)
+{
+	memset(display, 0, 8);
+	for (int i=snake_tail; i != snake_head; i = (i+1) % SNAKE_MAX)
+		display[snake[i][0]] |= 1 << snake[i][1];
+	display[food[0]] |= 1 << food[1];
+	refresh_display();
+}
+
+static void snake_step(void)
+{
+	if (buttons[0])
+		snake_dir = (snake_dir+3) % 4;
+	else if (buttons[1])
+		snake_dir = (snake_dir+1) % 4;
+
+	int hi = (snake_head + SNAKE_MAX - 1) % SNAKE_MAX;
+	int x = snake[hi][0] + dirs[snake_dir][0];
+	int y = snake[hi][1] + dirs[snake_dir][1];
+
+	if (x < 0 || x > 7 || y < 0 || y > 7)
+		return;
+
+	snake[snake_head][0] = x;
+	snake[snake_head][1] = y;
+	snake_head = (snake_head + 1) % SNAKE_MAX;
+
+	if (x == food[0] && y == food[1])
+		gen_food();
+	else
+		snake_tail = (snake_tail + 1) % SNAKE_MAX;
+
+	snake_show();
+}
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_GPIOC);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	// PB12 = display DIN
+	// PB13 = display CS*
+	// PB14 = display CLK
+	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_OPENDRAIN, GPIO12 | GPIO13 | GPIO14);
+	gpio_clear(GPIOB, GPIO12);
+	gpio_set(GPIOB, GPIO13);
+	gpio_clear(GPIOB, GPIO14);
+
+	// PA0 = left button
+	// PA1 = right button
+	gpio_set_mode(GPIOA, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, GPIO0 | GPIO1);
+	gpio_set(GPIOA, GPIO0 | GPIO1);
+
+	refresh_display();
+	set_reg(9, 0);
+	set_reg(10, 0);	// intensity
+	set_reg(11, 7);
+	set_reg(13, 0);	// test
+	set_reg(12, 1);	// shutdown
+
+	snake_init();
+	snake_show();
+
+	for (;;) {
+		buttons[0] = buttons[1] = 0;
+		for (int i=0; i<1000000; i++) {
+			if (!gpio_get(GPIOA, GPIO0))
+				buttons[0] = 1;
+			if (!gpio_get(GPIOA, GPIO1))
+				buttons[1] = 1;
+			asm volatile ("");
+		}
+
+		gpio_toggle(GPIOC, GPIO13);
+		snake_step();
+	}
+}

src/timer1-clock/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=timer
+OBJS=timer.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/timer1-clock/timer.c

@@ -0,0 +1,34 @@
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/timer.h>
+
+static void delay_ms(unsigned int ms)
+{
+	timer_set_period(TIM3, 2*ms);
+	timer_enable_counter(TIM3);
+	while (TIM_CR1(TIM3) & TIM_CR1_CEN)
+		;
+}
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_TIM3);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	timer_set_prescaler(TIM3, 35999);	// 72 MHz / 36000 = 2 kHz
+	timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_DOWN);
+	timer_one_shot_mode(TIM3);
+
+	for (;;) {
+		gpio_clear(GPIOC, GPIO13);
+		delay_ms(100);
+		gpio_set(GPIOC, GPIO13);
+		delay_ms(500);
+	}
+
+	return 0;
+}

src/timer2-irq/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=timer
+OBJS=timer.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/timer2-irq/timer.c

@@ -0,0 +1,36 @@
+#include <libopencm3/cm3/nvic.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/timer.h>
+
+void tim3_isr(void)
+{
+	if (TIM_SR(TIM3) & TIM_SR_UIF) {
+		TIM_SR(TIM3) &= ~TIM_SR_UIF;
+		gpio_toggle(GPIOC, GPIO13);
+	}
+}
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_TIM3);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	timer_set_prescaler(TIM3, 35999);	// 72 MHz / 36000 = 2 kHz
+	timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
+	timer_set_period(TIM3, 199);		// 200 ticks = 100 ms
+	timer_update_on_overflow(TIM3);
+	timer_enable_irq(TIM3, TIM_DIER_UIE);
+	nvic_enable_irq(NVIC_TIM3_IRQ);
+	timer_enable_counter(TIM3);
+
+	for (;;) {
+		asm volatile ("wfi");
+	}
+
+	return 0;
+}

src/timer3-oc/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=timer
+OBJS=timer.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/timer3-oc/timer.c

@@ -0,0 +1,37 @@
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/timer.h>
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_TIM3);
+	rcc_periph_reset_pulse(RST_TIM3);	// XXX
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+	gpio_set(GPIOC, GPIO13);
+
+	// PB0 = TIM3_CH3
+	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO0);
+
+	timer_set_prescaler(TIM3, 35999);	// 72 MHz / 36000 = 2 kHz
+	timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
+	timer_set_period(TIM3, 1999);
+	timer_update_on_overflow(TIM3);
+
+	timer_set_oc_mode(TIM3, TIM_OC3, TIM_OCM_PWM1);
+	timer_set_oc_value(TIM3, TIM_OC3, 500);
+	timer_set_oc_polarity_high(TIM3, TIM_OC3);
+	timer_enable_oc_output(TIM3, TIM_OC3);
+
+	timer_enable_counter(TIM3);
+
+	for (;;) {
+		asm volatile ("wfi");
+	}
+
+	return 0;
+}

src/timer4-pwm/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=timer
+OBJS=timer.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/timer4-pwm/timer.c

@@ -0,0 +1,37 @@
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/timer.h>
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_TIM3);
+	rcc_periph_reset_pulse(RST_TIM3);	// XXX
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+	gpio_set(GPIOC, GPIO13);
+
+	// PB0 = TIM3_CH3
+	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO0);
+
+	timer_set_prescaler(TIM3, 1);		// 72 MHz / 2 = 36 MHz
+	timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
+	timer_set_period(TIM3, 999);		// 36 MHz / 1000 = 36 kHz
+	timer_update_on_overflow(TIM3);
+
+	timer_set_oc_mode(TIM3, TIM_OC3, TIM_OCM_PWM1);
+	timer_set_oc_value(TIM3, TIM_OC3, 150);
+	timer_set_oc_polarity_high(TIM3, TIM_OC3);
+	timer_enable_oc_output(TIM3, TIM_OC3);
+
+	timer_enable_counter(TIM3);
+
+	for (;;) {
+		asm volatile ("wfi");
+	}
+
+	return 0;
+}

src/timer5-pwm/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=timer
+OBJS=timer.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/timer5-pwm/timer.c

@@ -0,0 +1,72 @@
+#include <libopencm3/cm3/nvic.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/timer.h>
+
+int up = 1;
+int pwm;
+
+void tim4_isr(void)
+{
+	if (TIM_SR(TIM4) & TIM_SR_UIF) {
+		TIM_SR(TIM4) &= ~TIM_SR_UIF;
+		if (up) {
+			pwm += 5;
+			if (pwm == 1000) {
+				pwm = 995;
+				up = 0;
+			}
+		} else {
+			pwm -= 5;
+			if (pwm < 0) {
+				pwm = 5;
+				up = 1;
+			}
+		}
+		timer_set_oc_value(TIM3, TIM_OC3, pwm);
+	}
+}
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_TIM3);
+	rcc_periph_clock_enable(RCC_TIM4);
+	rcc_periph_reset_pulse(RST_TIM3);	// XXX
+	rcc_periph_reset_pulse(RST_TIM4);	// XXX
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+	gpio_set(GPIOC, GPIO13);
+
+	// PB0 = TIM3_CH3
+	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO0);
+
+	timer_set_prescaler(TIM3, 1);		// 72 MHz / 2 = 36 MHz
+	timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
+	timer_set_period(TIM3, 999);		// 36 MHz / 1000 = 36 kHz
+	timer_update_on_overflow(TIM3);
+
+	timer_set_oc_mode(TIM3, TIM_OC3, TIM_OCM_PWM1);
+	timer_set_oc_value(TIM3, TIM_OC3, 50);
+	timer_set_oc_polarity_high(TIM3, TIM_OC3);
+	timer_enable_oc_output(TIM3, TIM_OC3);
+
+	timer_enable_counter(TIM3);
+
+	timer_set_prescaler(TIM4, 35999);	// 72 MHz / 36000 = 2 kHz
+	timer_set_mode(TIM4, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
+	timer_set_period(TIM4, 2);		// 2 kHz / 2 = 1 kHz
+	timer_update_on_overflow(TIM4);
+	timer_enable_irq(TIM4, TIM_DIER_UIE);
+	nvic_enable_irq(NVIC_TIM4_IRQ);
+	timer_enable_counter(TIM4);
+
+	for (;;) {
+		asm volatile ("wfi");
+	}
+
+	return 0;
+}

src/usart1/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=usart
+OBJS=usart.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/usart1/usart.c

@@ -0,0 +1,38 @@
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/usart.h>
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_USART1);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	// PA10 = RX1, PA9 = TX1
+	gpio_set_mode(GPIOA, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, GPIO10);
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO9);
+
+	usart_set_baudrate(USART1, 115200);
+	usart_set_databits(USART1, 8);
+	usart_set_stopbits(USART1, USART_STOPBITS_1);
+	usart_set_mode(USART1, USART_MODE_TX_RX);
+	usart_set_parity(USART1, USART_PARITY_NONE);
+	usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);
+	usart_enable(USART1);
+
+	int c = 32;
+	for (;;) {
+		gpio_toggle(GPIOC, GPIO13);
+
+		usart_send(USART1, c);
+		usart_wait_send_ready(USART1);
+
+		c++;
+		if (c == 127)
+			c = 32;
+	}
+}

src/usart2/Makefile

@@ -0,0 +1,6 @@
+ROOT=..
+BINARY=usart
+OBJS=usart.o
+LIB_OBJS=
+
+include $(ROOT)/example.mk

src/usart2/usart.c

@@ -0,0 +1,36 @@
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/usart.h>
+
+int main(void)
+{
+	rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_USART1);
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+
+	// PA10 = RX1, PA9 = TX1
+	gpio_set_mode(GPIOA, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, GPIO10);
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO9);
+
+	usart_set_baudrate(USART1, 115200);
+	usart_set_databits(USART1, 8);
+	usart_set_stopbits(USART1, USART_STOPBITS_1);
+	usart_set_mode(USART1, USART_MODE_TX_RX);
+	usart_set_parity(USART1, USART_PARITY_NONE);
+	usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);
+	usart_enable(USART1);
+
+	for (;;) {
+		gpio_toggle(GPIOC, GPIO13);
+
+		usart_wait_recv_ready(USART1);
+		int c = usart_recv(USART1);
+
+		usart_send(USART1, c);
+		usart_wait_send_ready(USART1);
+	}
+}