first commit

src/uart.c

@@ -0,0 +1,37 @@
+#include "uart.h"
+
+#include "ch32v003fun.h"
+
+// Write multiple chars to UART
+int _write(int fd, const char *buf, int size) {
+  for (int i = 0; i < size; i++) {
+    while (!(USART2->STATR & USART_FLAG_TC));  // Wait for transmission complete
+    USART2->DATAR = *buf++;                    // Send character
+  }
+  return size;
+}
+
+// Write a single char to UART
+int putchar(int c) {
+  while (!(USART2->STATR & USART_FLAG_TC));  // Wait for transmission complete
+  USART2->DATAR = (uint8_t)c;                // Send character
+  return 1;
+}
+
+void setup_uart(int uart_brr) {
+  // RCC->APB2PCENR |= RCC_APB2Periph_GPIOA;   // Enable GPIOA on APB2
+  RCC->APB1PCENR |= RCC_APB1Periph_USART2;  // Enable USART2 on APB1
+
+  GPIOA->CFGLR &= ~(0xf << (4 * 2));  // Clear bits for PA2
+  GPIOA->CFGLR |= (GPIO_Speed_10MHz | GPIO_CNF_OUT_PP_AF)
+                  << (4 * 2);  // Set PA2 as AF
+
+  // USART configuration: 115200 baud rate, 8 data bits, no parity, 1 stop bit
+  USART2->CTLR1 = USART_WordLength_8b | USART_Parity_No | USART_Mode_Tx;
+  USART2->CTLR2 = USART_StopBits_1;
+  USART2->CTLR3 = USART_HardwareFlowControl_None;
+
+  USART2->BRR = uart_brr;
+  // Enable USART2
+  USART2->CTLR1 |= CTLR1_UE_Set;
+}