1 files changed, 70 insertions, 0 deletions
diff --git a/usart/main.c b/usart/main.c
new file mode 100644
index 0000000..b92cbbe
--- /dev/null
+++ b/usart/main.c
@@ -0,0 +1,70 @@
+
+
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/usart.h>
+
+
+#define DELAY 1000000
+
+
+void clock_init(void);
+void gpio_init(void);
+void usart_init(void);
+void delay(void);
+
+
+int main(void)
+{
+	clock_init();
+	gpio_init();
+	usart_init();
+
+	while(1){
+		delay();
+		usart_send_blocking(USART3, 'H');
+		usart_send_blocking(USART3, 'e');
+		usart_send_blocking(USART3, 'l');
+		usart_send_blocking(USART3, 'l');
+		usart_send_blocking(USART3, 'o');
+		usart_send_blocking(USART3, '\r');
+		usart_send_blocking(USART3, '\n');
+		delay();
+	}
+
+	return 0;
+}
+
+
+void clock_init(void)
+{
+	rcc_periph_clock_enable(RCC_GPIOB);   // for USART3
+    rcc_periph_clock_enable(RCC_USART3);  // for USART3
+}
+
+
+void gpio_init(void)
+{
+	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_USART3_TX);  // TX setup
+	gpio_set_mode(GPIOB, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, GPIO_USART3_RX);  // RX setup
+}
+
+
+void usart_init(void)
+{
+	usart_set_baudrate(USART3, 9600);
+	usart_set_databits(USART3, 8);
+	usart_set_flow_control(USART3, USART_FLOWCONTROL_NONE);
+	usart_set_mode(USART3, USART_MODE_TX_RX);
+	usart_set_parity(USART3, USART_PARITY_NONE);
+	usart_set_stopbits(USART3, USART_STOPBITS_1);
+	usart_enable(USART3);
+}
+
+
+void delay(void)
+{
+	for (int i = 0; i < DELAY; i++) {
+		__asm__("nop");
+	}
+}