1.0

App/retarget.c

@@ -0,0 +1,99 @@
+#include "retarget.h"
+
+#include <stdint.h>
+#include <stdio.h>
+
+#include "cmsis_os.h"
+#include "usbd_cdc_if.h"
+
+/*
+ * 说明：
+ * 1. 这里默认使用 FreeRTOS 的 CMSIS-RTOS2 接口
+ * 2. printf 最终会走到 _write()
+ * 3. _write() 内部调用 CDC_Transmit_FS() 发送到 USB 虚拟串口
+ * 4. 为避免多个任务同时 printf 打花，这里提供互斥锁
+ */
+
+static osMutexId_t s_retarget_mutex = NULL;
+static uint8_t s_inited = 0U;
+
+/* 互斥锁属性 */
+static const osMutexAttr_t s_retarget_mutex_attr = {
+  .name = "retargetMutex"
+};
+
+void Retarget_Init(void)
+{
+  if (s_inited != 0U)
+  {
+    return;
+  }
+
+  /* 只有在内核启动后创建互斥量才有意义 */
+  if (osKernelGetState() == osKernelRunning)
+  {
+    s_retarget_mutex = osMutexNew(&s_retarget_mutex_attr);
+  }
+
+  s_inited = 1U;
+}
+
+void Retarget_Lock(void)
+{
+  if ((s_retarget_mutex != NULL) && (osKernelGetState() == osKernelRunning))
+  {
+    (void)osMutexAcquire(s_retarget_mutex, osWaitForever);
+  }
+}
+
+void Retarget_Unlock(void)
+{
+  if ((s_retarget_mutex != NULL) && (osKernelGetState() == osKernelRunning))
+  {
+    (void)osMutexRelease(s_retarget_mutex);
+  }
+}
+
+/*
+ * GNU 工具链 printf 重定向
+ * 注意：
+ * - 不要在中断里调用 printf
+ * - USB CDC 忙时最多等待 20ms
+ * - 等待期间 osDelay(1) 让出 CPU
+ */
+int _write(int file, char *ptr, int len)
+{
+  uint32_t start_tick;
+  uint8_t result;
+
+  (void)file;
+
+  if ((ptr == NULL) || (len <= 0))
+  {
+    return 0;
+  }
+
+  start_tick = HAL_GetTick();
+
+  while (1)
+  {
+    result = CDC_Transmit_FS((uint8_t *)ptr, (uint16_t)len);
+
+    if (result == USBD_OK)
+    {
+      return len;
+    }
+
+    /* USB 还没准备好或者正忙，最多等 20ms */
+    if ((HAL_GetTick() - start_tick) > 20U)
+    {
+      return 0;
+    }
+
+    /* 在 FreeRTOS 下主动让出 CPU */
+    if (osKernelGetState() == osKernelRunning)
+    {
+      osDelay(1);
+    }
+  }
+}