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printf/retarget.c

@@ -0,0 +1,94 @@
+// All credit to Carmine Noviello for this code
+// https://github.com/cnoviello/mastering-stm32/blob/master/nucleo-f030R8/system/src/retarget/retarget.c
+
+#include <_ansi.h>
+#include <_syslist.h>
+#include <errno.h>
+#include <sys/time.h>
+#include <sys/times.h>
+#include <limits.h>
+#include <signal.h>
+#include <../Inc/retarget.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#if !defined(OS_USE_SEMIHOSTING)
+
+#define STDIN_FILENO  0
+#define STDOUT_FILENO 1
+#define STDERR_FILENO 2
+
+UART_HandleTypeDef *gHuart;
+
+void RetargetInit(UART_HandleTypeDef *huart) {
+  gHuart = huart;
+
+  /* Disable I/O buffering for STDOUT stream, so that
+   * chars are sent out as soon as they are printed. */
+  setvbuf(stdout, NULL, _IONBF, 0);
+}
+
+int _isatty(int fd) {
+  if (fd >= STDIN_FILENO && fd <= STDERR_FILENO)
+    return 1;
+
+  errno = EBADF;
+  return 0;
+}
+
+int _write(int fd, char* ptr, int len) {
+  HAL_StatusTypeDef hstatus;
+
+  if (fd == STDOUT_FILENO || fd == STDERR_FILENO) {
+    hstatus = HAL_UART_Transmit(gHuart, (uint8_t *) ptr, len, HAL_MAX_DELAY);
+    if (hstatus == HAL_OK)
+      return len;
+    else
+      return EIO;
+  }
+  errno = EBADF;
+  return -1;
+}
+
+int _close(int fd) {
+  if (fd >= STDIN_FILENO && fd <= STDERR_FILENO)
+    return 0;
+
+  errno = EBADF;
+  return -1;
+}
+
+int _lseek(int fd, int ptr, int dir) {
+  (void) fd;
+  (void) ptr;
+  (void) dir;
+
+  errno = EBADF;
+  return -1;
+}
+
+int _read(int fd, char* ptr, int len) {
+  HAL_StatusTypeDef hstatus;
+
+  if (fd == STDIN_FILENO) {
+    hstatus = HAL_UART_Receive(gHuart, (uint8_t *) ptr, 1, HAL_MAX_DELAY);
+    if (hstatus == HAL_OK)
+      return 1;
+    else
+      return EIO;
+  }
+  errno = EBADF;
+  return -1;
+}
+
+int _fstat(int fd, struct stat* st) {
+  if (fd >= STDIN_FILENO && fd <= STDERR_FILENO) {
+    st->st_mode = S_IFCHR;
+    return 0;
+  }
+
+  errno = EBADF;
+  return 0;
+}
+
+#endif //#if !defined(OS_USE_SEMIHOSTING)

printf/retarget.h

@@ -0,0 +1,18 @@
+// All credit to Carmine Noviello for this code
+// https://github.com/cnoviello/mastering-stm32/blob/master/nucleo-f030R8/system/include/retarget/retarget.h
+
+#ifndef _RETARGET_H__
+#define _RETARGET_H__
+
+#include "stm32l4xx_hal.h"
+#include <sys/stat.h>
+
+void RetargetInit(UART_HandleTypeDef *huart);
+int _isatty(int fd);
+int _write(int fd, char* ptr, int len);
+int _close(int fd);
+int _lseek(int fd, int ptr, int dir);
+int _read(int fd, char* ptr, int len);
+int _fstat(int fd, struct stat* st);
+
+#endif //#ifndef _RETARGET_H__

printf/usage.md

@@ -0,0 +1,17 @@
+Right-click on the syscalls.c file and select Properties. Under C/C++ Build > Settings, check Exclude resource from build.
+
+in main.c: <br/>
+```c
+#include <stdio.h>
+#include "retarget.h"
+char buf[100];
+RetargetInit(&huart1);
+```
+
+Example:<br/>
+```c
+printf("\r\nYour name: ");
+scanf("%s", buf);
+printf("\r\nHello, %s!\r\n", buf);
+
+```