STM32，嵌入式系统中简单shell的实现
对于嵌入式系统而言，特别对于没有使用操作系统，裸机运行程序的嵌入式系统，如何高效便捷的进行系统调试往往是一个比较令人头疼的问题。不久前，我接触到一个国产嵌入式操作系统，Thread RTOS，其中，该系统集成的finsh shell工具让我有种眼前一亮的感觉，它将shell工具引入到嵌入式系统中，极大的方便了系统的调试。
然而，finsh shell运行在操作系统之上，体积也比较大，对于某些小型嵌入式设备，基本是与其无缘了，既然如此，我们为何不自己编写一个shell呢。
我们首先对shell的运行原理进行分析，通过在命令行输入命令，shell对命令进行解析，然后执行相应的操作，更通俗的，就是使用输入的字符串，匹配到对应的函数，然后执行。那么，我们需要建立一个命令-函数的一一对应的关系，定义结构体。
typedef struct
{
uint8_t *name; //shell命令名称
shellFunction function; //shell命令函数
uint8_t *desc; //shell命令描述
}SHELL_CommandTypeDef; //shell命令定义其中，shellFunction为函数指针类型，定义为
typedef void (*shellFunction)();有了定义之后，我们建立一个表，将所有的命令以及对应的函数进行声明
/**
* shell 命令表，使用 {command, function, description} 的格式添加命令
* 其中
* command 为命令，字符串格式，长度不能超过 SHELL_PARAMETER_MAX_LENGTH
* 若不使用带参命令，则长度不超过SHELL_COMMAND_MAX_LENGTH
* function 为该命令调用的函数，支持(void *)(void)类型的无参函数以及与带参主函数
* 类似的(void *)(uint32_t argc, uint8_t *argv[])类型的带参函数，其中，
* argc 为参数个数，argv 为参数，参数皆为字符串格式，需自行进行数据转换
* description 为对命令的描述，字符串格式
*/
const SHELL_CommandTypeDef shellCommandList[] =
{
/*command function description*/
{(uint8_t *)"letter", shellLetter, (uint8_t *)"letter shell"},
{(uint8_t *)"reboot", shellReboot, (uint8_t *)"reboot system"},
{(uint8_t *)"help", shellShowCommandList, (uint8_t *)"show command list"},
{(uint8_t *)"clear", shellClear, (uint8_t *)"clear command line"},
{(uint8_t *)"iap", iapMain, (uint8_t *)"iap"},
{(uint8_t *)"tftp", iapTftp, (uint8_t *)"start TFTP server"},
{(uint8_t *)"userApp", iapJumpToApplication, (uint8_t *)"run user application"},
{(uint8_t *)"erase", (void (*)())iapErase, (uint8_t *)"erase user application"},
#if SHELL_USE_PARAMETER == 1 /*带参函数命令*/
{(uint8_t *)"paraTest", (void (*)())shellParaTest, (uint8_t *)"test parameter"},
#endif
};然后，我们只需要获得输入的命令，并将其和命令表中的命令进行匹配，然后执行相应的函数即可，完整代码如下：
/*******************************************************************************
*@function shellHandler
*@brief shell处理函数
*@param receiveData 接收到的数据
*@retval None
*@author Letter
*@note 此函数被shellMain函数调用，若使用shellMain阻塞式运行shell，直接调用
* shellMain函数即可，但不建议这样做，建议在无操作系统情况下，在shell
* 输入触发的中断中调用此函数（通常为串口中断），此时无需调用shellMain，
* shell也为非阻塞式，操作系统情况下，通常将此函数交给shell输入设备的
* 任务处理
*******************************************************************************/
void shellHandler(uint8_t receiveData)
{
static uint8_t runFlag;
static CONTROL_Status controlFlag = CONTROL_FREE;
switch (receiveData)
{
case '\r':
case '\n':
if (shellCommandFlag >= SHELL_COMMAND_MAX_LENGTH - 1)
{
shellDisplay("\r\nError: Command is too long\r\n");
shellCommandBuff[shellCommandFlag] = 0;
shellCommandFlag = 0;
shellDisplay(SHELL_COMMAND);
break;
}
if (shellCommandFlag == 0)
{
shellDisplay(SHELL_COMMAND);
break;
}
else
{
shellCommandBuff[shellCommandFlag++] = 0;
#if SHELL_USE_PARAMETER == 1
commandCount = 0;
uint8_t j = 0;
for (int8_t i = 0; i < shellCommandFlag; i++)
{
if (shellCommandBuff[i] != ' ' &&
shellCommandBuff[i] != '\t' &&
shellCommandBuff[i] != 0)
{
commandPara[commandCount][j++] = shellCommandBuff[i];
}
else
{
if (j != 0)
{
commandPara[commandCount][j] = 0;
commandCount ++;
j = 0;
}
}
}
shellCommandFlag = 0;
if (commandCount == 0) //是否为无效指令
{
shellDisplay(SHELL_COMMAND);
break;
}
#if SHELL_USE_HISTORY ==1
shellStringCopy(shellHistoryCommand[shellHistoryFlag++], shellCommandBuff);
if (++shellHistoryCount > SHELL_HISTORY_MAX_NUMBER)
{
shellHistoryCount = SHELL_HISTORY_MAX_NUMBER;
}
if (shellHistoryFlag >= SHELL_HISTORY_MAX_NUMBER)
{
shellHistoryFlag = 0;
}
shellHistoryOffset = 0;
#endif
shellDisplay("\r\n");
runFlag = 0;
for (int8_t i = sizeof(shellCommandList) / sizeof(SHELL_CommandTypeDef) - 1;
i >= 0; i--)
{
if (strcmp((const char *)commandPara[0],
(const char *)shellCommandList[i].name) == 0)
{
runFlag = 1;
shellCommandList[i].function(commandCount, commandPointer);
break;
}
}
#else /*SHELL_USE_PARAMETER == 1*/
shellCommandBuff[shellCommandFlag] = 0;
shellCommandFlag = 0;
shellDisplay("\r\n");
runFlag = 0;
for (int8_t i = sizeof(shellCommandList) / sizeof(SHELL_CommandTypeDef) - 1;
i >= 0; i--)
{
if (strcmp((const char *)shellCommandBuff,
(const char *)shellCommandList[i].name) == 0)
{
runFlag = 1;
shellCommandList[i].function();
break;
}
}
#endif /*SHELL_USE_PARAMETER == 1*/
if (runFlag == 0)
{
shellDisplay("Command not found");
}
}
shellDisplay(SHELL_COMMAND);
break;
case 0x08: //退格
if (shellCommandFlag != 0)
{
shellCommandFlag--;
shellBackspace(1);
}
break;
case '\t': //制表符
#if SHELL_USE_HISTORY == 1
if (shellHistoryCount != 0)
{
shellBackspace(shellCommandFlag);
shellCommandFlag = shellStringCopy(shellCommandBuff,
shellHistoryCommand[(shellHistoryFlag + SHELL_HISTORY_MAX_NUMBER - 1)
% SHELL_HISTORY_MAX_NUMBER]);
shellDisplay(shellCommandBuff);
}
else //无历史命令，输入help
{
shellBackspace(shellCommandFlag);
shellCommandFlag = 4;
shellStringCopy(shellCommandBuff, (uint8_t *)"help");
shellDisplay(shellCommandBuff);
}
#endif
break;
case 0x1B: //控制键
controlFlag = CONTROL_STEP_ONE;
break;
default:
switch ((uint8_t)controlFlag)
{
case CONTROL_STEP_TWO:
if (receiveData == 0x41) //方向上键
{
#if SHELL_USE_HISTORY == 1
shellBackspace(shellCommandFlag);
if (shellHistoryOffset--
<= -((shellHistoryCount > shellHistoryFlag)
? shellHistoryCount : shellHistoryFlag))
{
shellHistoryOffset
= -((shellHistoryCount > shellHistoryFlag)
? shellHistoryCount : shellHistoryFlag);
}
shellCommandFlag = shellStringCopy(shellCommandBuff,
shellHistoryCommand[(shellHistoryFlag + SHELL_HISTORY_MAX_NUMBER
+ shellHistoryOffset) % SHELL_HISTORY_MAX_NUMBER]);
shellDisplay(shellCommandBuff);
#else
//shellDisplay("up\r\n");
#endif
}
else if (receiveData == 0x42) //方向下键
{
#if SHELL_USE_HISTORY == 1
if (++shellHistoryOffset >= 0)
{
shellHistoryOffset = -1;
break;
}
shellBackspace(shellCommandFlag);
shellCommandFlag = shellStringCopy(shellCommandBuff,
shellHistoryCommand[(shellHistoryFlag + SHELL_HISTORY_MAX_NUMBER
+ shellHistoryOffset) % SHELL_HISTORY_MAX_NUMBER]);
shellDisplay(shellCommandBuff);
#else
//shellDisplay("down\r\n");
#endif
}
else if (receiveData == 0x43) //方向右键
{
//shellDisplay("right\r\n");
}
else if (receiveData == 0x44) //方向左键
{
//shellDisplay("left\r\n");
}
else
{
controlFlag = CONTROL_FREE;
goto normal;
}
break;
case CONTROL_STEP_ONE:
if (receiveData == 0x5B)
{
controlFlag = CONTROL_STEP_TWO;
}
else
{
controlFlag = CONTROL_FREE;
goto normal;
}
break;
case CONTROL_FREE: //正常按键处理
normal: if (shellCommandFlag < SHELL_COMMAND_MAX_LENGTH - 1)
{
shellCommandBuff[shellCommandFlag++] = receiveData;
shellDisplayByte(receiveData);
}
else
{
shellCommandFlag++;
shellDisplayByte(receiveData);
}
break;
}
break;
}
}我们使用串口进行命令的输入和输出，在输入命令并回车之后，程序解析命令，根据空格将输入分开为命令和参数，对命令进行匹配，匹配到命令之后，执行函数。
完整代码