我正在测试从Raspberry PI& uart读取数据。 我有USB转UART适配器并连接PI的USB端口和PI的UART(g,Rx,Tx)。 然后运行USB端口的代码。代码每100毫秒将数据发送到uart。
#!/usr/bin/env python
import time
import serial
ser = serial.Serial(
port='/dev/ttyUSB0',
baudrate = 9600,
parity=serial.PARITY_NONE,
stopbits=serial.STOPBITS_ONE,
bytesize=serial.EIGHTBITS,
timeout=1
)
counter=0
while 1:
print counter
if counter>=1000:
ser.write('\r')
else:
ser.write('%d \n'%(counter))
time.sleep(0.1)//100msec
counter += 1
然后在我的UART端,C ++程序从UART读取数据。
代码如下,每100毫秒I call the ReadData_helper function using a timer
。
void InterfaceUART::PortInitialization()
{
fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY | O_NDELAY );
if (fd <0) {perror(MODEMDEVICE); exit(-1); }
tcgetattr(fd,&oldtio); /* save current serial port settings */
bzero(&newtio, sizeof(newtio)); /* clear struct for new port settings */
/*
BAUDRATE: Set bps rate. You could also use cfsetispeed and cfsetospeed.
CRTSCTS : output hardware flow control (only used if the cable has
all necessary lines. See sect. 7 of Serial-HOWTO)
CS8 : 8n1 (8bit,no parity,1 stopbit)
CLOCAL : local connection, no modem contol
CREAD : enable receiving characters
*/
newtio.c_cflag = B9600 | CRTSCTS | CS8 | CLOCAL | CREAD;
/*
IGNPAR : ignore bytes with parity errors
ICRNL : map CR to NL (otherwise a CR input on the other computer
will not terminate input)
otherwise make device raw (no other input processing)
*/
newtio.c_iflag = IGNPAR | ICRNL;
/*
Raw output.
*/
newtio.c_oflag = 0;
/*
ICANON : enable canonical input
disable all echo functionality, and don't send signals to calling program
*/
newtio.c_lflag = ICANON;
/*set signal*/
//saio.sa_handler = signal_handler_IO;
//saio.sa_flags = 0;
//saio.sa_restorer = NULL;
//sigaction(SIGIO,&saio,NULL);
fcntl(fd, F_SETFL, FNDELAY);//|FASYNC//FNDELAY ,#FNDELAY makes read function to return with 0 if no characters are available on the port and if FNDELAY == 0, it is blocking mode
fcntl(fd, F_SETOWN, getpid());
/*
initialize all control characters
default values can be found in /usr/include/termios.h, and are given
in the comments, but we don't need them here
*/
newtio.c_cc[VINTR] = 0; /* Ctrl-c */
newtio.c_cc[VQUIT] = 0; /* Ctrl-\ */
newtio.c_cc[VERASE] = 0; /* del */
newtio.c_cc[VKILL] = 0; /* @ */
newtio.c_cc[VEOF] = 4; /* Ctrl-d */
newtio.c_cc[VTIME] = 0; /* inter-character timer unused */
newtio.c_cc[VMIN] = 1; /* blocking read until 1 character arrives */
newtio.c_cc[VSWTC] = 0; /* '\0' */
newtio.c_cc[VSTART] = 0; /* Ctrl-q */
newtio.c_cc[VSTOP] = 0; /* Ctrl-s */
newtio.c_cc[VSUSP] = 0; /* Ctrl-z */
newtio.c_cc[VEOL] = 0; /* '\0' */
newtio.c_cc[VREPRINT] = 0; /* Ctrl-r */
newtio.c_cc[VDISCARD] = 0; /* Ctrl-u */
newtio.c_cc[VWERASE] = 0; /* Ctrl-w */
newtio.c_cc[VLNEXT] = 0; /* Ctrl-v */
newtio.c_cc[VEOL2] = 0; /* '\0' */
/*
now clean the modem line and activate the settings for the port
*/
tcflush(fd, TCIFLUSH);
tcsetattr(fd,TCSANOW,&newtio);
return;
}
void *InterfaceUART::ReadData(void *p){
//InterfaceUART *app = (InterfaceUART*)p;
res = read(fd,buf,255);
//buf[res] = 0;
float *a = (float*)malloc(sizeof(float));
*a = (float)atof(buf);
//pthread_exit((void*)&a); //success
return (void*)a;
}
void *InterfaceUART::ReadData_helper (void *p){
InterfaceUART *app = (InterfaceUART*)p;
return ((InterfaceUART*)p)->ReadData(app);
}
接口可以工作一段时间,然后重复读取相同的数据。
deg is : 0 speed is : 135
time diff 0
deg is : 0 speed is : 136
time diff 1
deg is : 0 speed is : 137
time diff 0
deg is : 0 speed is : 138
time diff 0
deg is : 0 speed is : 139
time diff 0
deg is : 0 speed is : 140
time diff 0
deg is : 0 speed is : 141
time diff 1
deg is : 0 speed is : 142
time diff 0
deg is : 0 speed is : 143
time diff 1
deg is : 0 speed is : 144
time diff 0
deg is : 0 speed is : 145
time diff 0
deg is : 0 speed is : 146
time diff 0
deg is : 0 speed is : 147
time diff 0
deg is : 0 speed is : 148
time diff 1
deg is : 0 speed is : 149
time diff 1
deg is : 0 speed is : 150
time diff 0
deg is : 0 speed is : 151
time diff 0
deg is : 0 speed is : 152
time diff 0
deg is : 0 speed is : 153
time diff 0
deg is : 0 speed is : 154
time diff 1
deg is : 0 speed is : 155
time diff 0
deg is : 0 speed is : 156
time diff 1
deg is : 0 speed is : 156
time diff 0
deg is : 0 speed is : 156
time diff 1
deg is : 0 speed is : 156
正确读取155,在156读取数据。 156不是固定的,它有时会随机停止71,有时是153等。达到一个数字后再也不会改变。
可能出现什么问题?
谢谢