我在我的 C++ 程序中使用 Windows API 通过串口连接 arduino。
arduino 每秒发送一个字节,c++ 程序应读取该字节并在屏幕上打印。
这是我的 arduino 代码。
void setup() {
Serial.begin(9600);
}
void loop() {
Serial.write('a');
delay(1000);
}
Serial类中有成员
//Serial comm handler
HANDLE hSerial;
//Connection status
bool connected;
//Get various information about the connection
COMSTAT status;
//Keep track of last error
DWORD errors;
//transform error message to be stored in a string variable
这是我的 C++ 程序中的读取函数
int Serial::ReadData(char buffer)
{
//Number of bytes we'll have read
DWORD bytesRead = 0;
//Use the ClearCommError function to get status info on the Serial port
ClearCommError(this->hSerial, &this->errors, &this->status);
cout << this->status.cbInQue << " Bytes in the queue have not been read" << endl;
//Check if there is something to read
if(this->status.cbInQue>0)
{
//Try to read the require number of chars, and return the number of read bytes on success
if(ReadFile(this->hSerial, (void *)&buffer, 1, &bytesRead, NULL) )
{
return bytesRead;
}
}
//If nothing has been read, or that an error was detected return 0
return 0;
}
如果需要,这是我的 Serial 构造函数
Serial::Serial(string portName, char use)
{
//We're not yet connected
this->connected = false;
DWORD authority;
if (use == 'w'){
authority = GENERIC_WRITE;
}
else if (use == 'r'){
cout << "read" << endl;
authority = GENERIC_READ;
}
else if (use == 'b'){
authority = GENERIC_READ | GENERIC_WRITE;
}
else{
cout << "the second parameter of the initialization of the Serial object is wrong" << endl;
cout << "It can only be w or r" << endl;
}
//Try to connect to the given port through CreateFile
this->hSerial = CreateFile(portName.c_str(),
authority,
0,
NULL,
OPEN_EXISTING,
0,
NULL);
//Check if the connection was successful
if(this->hSerial==INVALID_HANDLE_VALUE)
{
cout << GetLastErrorAsString() << endl;
}
else
{
//If connected we try to set the comm parameters
DCB dcbSerialParams = {0};
//Try to get the current
if (!GetCommState(this->hSerial, &dcbSerialParams))
{
//If impossible, show an error
printf("failed to get current serial parameters!");
}
else
{
//Define serial connection parameters for the arduino board
dcbSerialParams.BaudRate=CBR_9600;
dcbSerialParams.ByteSize=8;
dcbSerialParams.StopBits=ONESTOPBIT;
dcbSerialParams.Parity=NOPARITY;
//Setting the DTR to Control_Enable ensures that the Arduino is properly
//reset upon establishing a connection
dcbSerialParams.fDtrControl = DTR_CONTROL_ENABLE;
//Set the parameters and check for their proper application
if(!SetCommState(hSerial, &dcbSerialParams))
{
printf("ALERT: Could not set Serial Port parameters");
}
else
{
//If everything went fine we're connected
this->connected = true;
//Flush any remaining characters in the buffers
PurgeComm(this->hSerial, PURGE_RXCLEAR | PURGE_TXCLEAR);
//We wait 2s as the arduino board will be reseting
Sleep(ARDUINO_WAIT_TIME);
}
}
}
}
这是我的主程序
int main(int argc, _TCHAR* argv[])
{
char use = 'r'; //r for read, w for write, b for both
Serial* SP = new Serial("COM4", use); // adjust as needed
char input;
int num_bytes_read;
while(SP->IsConnected())
{
cout << "connect successes!" << endl;
num_bytes_read = SP->ReadData(input);
cout << num_bytes_read << " " << (int) input << endl;
Sleep(1000);
}
return 0;
}
打印到屏幕时,我将 char 变量“input”转换为 int 以检查存储在 char 变量中的值的 ascii 代码。
最后就是我的c++程序的输出
connect successes!
1 Bytes in the queue have not been read
1 0
看起来确实收到了数据,但为什么打印的不是'a'而是NULL?
我使用 Arduino/Genuino Uno(这是我在 Arduino IDE 中选中“工具”按钮时看到的)和 Windows 10
感谢您考虑我的请求!
最佳答案
在 C++ 中,参数通过 vaule 传递...除非它们通过引用传递。所以改变这一行:
int Serial::ReadData(char buffer)
到:
int Serial::ReadData(char &buffer)
否则,当您读入 buffer
时您实际上正在读入 ReadData
的局部变量并且不要修改 input
来自 main
.
可以说,如果你把它改成这样会更好:
int Serial::ReadData(char *buffer, int len)
然后,在 main
你称之为写作:
num_bytes_read = SP->ReadData(&input, 1);
这样以后,当你想读取更多的数据时,只需调用一次即可。
关于c++ - 从 arduino 读取到 c++ 程序时保持接收 NULL,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38263790/