i2c: printf redirection working

nucleo-wb55-i2c/Core/Src/main.c

@@ -22,7 +22,7 @@
 
 /* Private includes ----------------------------------------------------------*/
 /* USER CODE BEGIN Includes */
-
+#include <stdio.h>
 /* USER CODE END Includes */
 
 /* Private typedef -----------------------------------------------------------*/
@@ -89,17 +89,22 @@ int main(void)
   MX_GPIO_Init();
   MX_USART1_UART_Init();
   /* USER CODE BEGIN 2 */
-
+#ifdef __GNUC__
+/* With GCC, small printf (option LD Linker->Libraries->Small printf
+   set to 'Yes') calls __io_putchar() */
+#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)
+#else
+#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)
+#endif /* __GNUC__ */
   /* USER CODE END 2 */
 
   /* Infinite loop */
   /* USER CODE BEGIN WHILE */
+  int index = 0;
   while (1)
   {
-  	if (HAL_UART_Transmit(&huart1, "TEST ", 6, 100) != HAL_OK) {
-      Error_Handler();
-    }
-    HAL_Delay(500);
+  	printf("test %d\n\r", index++);
+    HAL_Delay(100);
     /* USER CODE END WHILE */
 
     /* USER CODE BEGIN 3 */
@@ -261,7 +266,19 @@ static void MX_GPIO_Init(void)
 }
 
 /* USER CODE BEGIN 4 */
+/**
+  * @brief  Retargets the C library printf function to the USART.
+  * @param  None
+  * @retval None
+  */
+PUTCHAR_PROTOTYPE
+{
+  /* Place your implementation of fputc here */
+  /* e.g. write a character to the USART1 and Loop until the end of transmission */
+  HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 0xFFFF);
 
+  return ch;
+}
 /* USER CODE END 4 */
 
 /**