From ed3f82222d567927cf20fa2d804d230fb5b5a715 Mon Sep 17 00:00:00 2001
From: Imbus <>
Date: Wed, 16 Jul 2025 17:33:10 +0200
Subject: [PATCH] Uart setup

---
 main.c | 42 +++++++++++++++++++++++++++++++++---------
 uart.c | 33 +++++++++++++++++++++++++--------
 2 files changed, 58 insertions(+), 17 deletions(-)

diff --git a/main.c b/main.c
index cf64bcd..8899a99 100644
--- a/main.c
+++ b/main.c
@@ -1,38 +1,62 @@
+#include "system.h"
+#include "uart.h"
 #include <libopencm3/cm3/nvic.h>
 #include <libopencm3/cm3/systick.h>
 #include <libopencm3/stm32/flash.h>
 #include <libopencm3/stm32/gpio.h>
 #include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/usart.h>
 #include <stdint.h>
-#include "system.h"
+#include <stdio.h>
 
 static void gpio_setup(void) {
-    rcc_periph_clock_enable(RCC_GPIOC);
     gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+    gpio_set(GPIOC, GPIO12);
+
+    /* Setup GPIO6 and 7 (in GPIO port A) for LED use. */
+    gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO12);
+}
+
+static void clock_setup(void) {
+    rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
+
+    /* Enable GPIOA clock (for LED GPIOs). */
+    rcc_periph_clock_enable(RCC_GPIOC);
+
+    /* Enable clocks for GPIO port A (for GPIO_USART1_TX) and USART1. */
+    rcc_periph_clock_enable(RCC_GPIOA);
+    rcc_periph_clock_enable(RCC_AFIO);
+    rcc_periph_clock_enable(RCC_USART1);
+
+    rcc_periph_clock_enable(RCC_GPIOC);
 }
 
 int main(void) {
-    rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]);
-    // rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSI_48MHZ]);
+    clock_setup();
     gpio_setup();
     sys_tick_setup();
+    usart_setup();
+
+    usart_send_blocking(USART1, 'H');
+    usart_send_blocking(USART1, 'e');
+    usart_send_blocking(USART1, 'l');
+    usart_send_blocking(USART1, 'l');
+    usart_send_blocking(USART1, 'o');
+    usart_send_blocking(USART1, '\n');
+
+    printf("Well hello");
 
     gpio_clear(GPIOC, GPIO13);
     gpio_set(GPIOC, GPIO13);
-    // gpio_set(GPIOB, GPIO6);    /* LED2 off */
-
-    // ticks = 0;
 
     uint64_t init = sys_ticks_get();
     while (sys_ticks_get() == init);
 
-    /* We call this handler every 1ms so 1000ms = 1s on/off. */
     uint64_t ref = 0;
     while (1) {
         if (sys_ticks_get() > ref) {
             ref += 500;
             gpio_toggle(GPIOC, GPIO13);
-            // while (sys_ticks_get() % 1000 == 0);
         }
     }
 
diff --git a/uart.c b/uart.c
index 7267a80..30dca19 100644
--- a/uart.c
+++ b/uart.c
@@ -1,20 +1,37 @@
-#include <libopencm3/stm32/usart.h>
-#include <libopencm3/stm32/rcc.h>
-#include <libopencm3/stm32/gpio.h>
 #include "uart.h"
+#include <errno.h>
+#include <libopencm3/cm3/nvic.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/usart.h>
+#include <stdio.h>
+
+int _write(int file, char *ptr, int len);
 
 void usart_setup(void) {
-    rcc_periph_clock_enable(RCC_GPIOA);
-    rcc_periph_clock_enable(RCC_USART1);
-
-    // Set PA9 (TX) to alternate function, push-pull
+    /* Setup GPIO pin GPIO_USART1_RE_TX on GPIO port B for transmit. */
     gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_USART1_TX);
 
+    /* Setup UART parameters. */
     usart_set_baudrate(USART1, 115200);
     usart_set_databits(USART1, 8);
     usart_set_stopbits(USART1, USART_STOPBITS_1);
-    usart_set_mode(USART1, USART_MODE_TX);
     usart_set_parity(USART1, USART_PARITY_NONE);
     usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);
+    usart_set_mode(USART1, USART_MODE_TX);
+
+    /* Finally enable the USART. */
     usart_enable(USART1);
 }
+
+int _write(int file, char *ptr, int len) {
+    int i;
+
+    if (file == 1) {
+        for (i = 0; i < len; i++) usart_send_blocking(USART1, ptr[i]);
+        return i;
+    }
+
+    errno = EIO;
+    return -1;
+}