支持shell，可以执行应用程序

mkrtos_user/lib/letter-shell/demo/mkrtos/shell_port.c

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+/**
+ * @file shell_port.c
+ * @author Letter (NevermindZZT@gmail.com)
+ * @brief
+ * @version 0.1
+ * @date 2019-02-22
+ *
+ * @copyright (c) 2019 Letter
+ *
+ */
+
+#include "shell.h"
+#include "cons_cli.h"
+#include "u_sleep.h"
+Shell shell;
+char shellBuffer[512];
+
+/**
+ * @brief 用户shell写
+ *
+ * @param data 数据
+ * @param len 数据长度
+ *
+ * @return unsigned short 写入实际长度
+ */
+signed short userShellWrite(char *data, unsigned short len)
+{
+    return cons_write((const char *)data, len);
+}
+
+/**
+ * @brief 用户shell读
+ *
+ * @param data 数据
+ * @param len 数据长度
+ *
+ * @return unsigned short 读取实际长度
+ */
+signed short userShellRead(char *data, unsigned short len)
+{
+    int ret = 0;
+    while (ret <= 0)
+    {
+        ret = cons_read((uint8_t *)data, len);
+        u_sleep_ms(5);
+    }
+}
+
+/**
+ * @brief 用户shell初始化
+ *
+ */
+void userShellInit(void)
+{
+    shell.write = userShellWrite;
+    shell.read = userShellRead;
+    shellInit(&shell, shellBuffer, 512);
+
+    while (1)
+    {
+        shellTask(&shell);
+    }
+}