Segmenting the strings received from serial port - c++

Question

I am receiving sensor datas through the serial port using Xbee module. The sensors are connected to Arduino and they are sending datas to the zigbee connected to my laptop. here, is the code i am using to show the received datas.
#include <fcntl.h>
#include <stdio.h>
#include <termios.h>
#include <stdlib.h>
#include <string.h>
/* Change to the baud rate of the port B2400, B9600, B19200 etc as per Arduino board is sending */
#define SPEED B9600
/* Change to the serial port you want to use /dev/ttyUSB0, /dev/ttyS0, etc. */
#define PORT "/dev/ttyS1"
/* Sensor raw datas */
int accLowX, accLowY, accLowZ;
int accHighX, accHighY, accHighZ;
int main( ){
int fd = open( PORT, O_RDONLY | O_NOCTTY );
if (fd <0) {perror(PORT); exit(-1); }
struct termios options;
bzero(&options, sizeof(options));
options.c_cflag = SPEED | CS8 | CLOCAL | CREAD | IGNPAR;
tcflush(fd, TCIFLUSH);
tcsetattr(fd, TCSANOW, &options);
int r;
char buf[255];
char sensorDatas[255];
while( 1 ){
r = read( fd, buf, 255 );
buf[r]=0;
memcpy(sensorDatas, buf, strlen(buf)+1);
printf( "%s", sensorDatas);
// separate the strings for sensor datas
//
}
}
My Output of received datas are:
56-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:341 AHZ:421
57-ALX:350 ALY:349 ALZ:351 AHX:354 AHY:341 AHZ:422
58-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
59-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
60-ALX:350 ALY:349 ALZ:351 AHX:352 AHY:342 AHZ:422
61-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:421
62-ALX:350 ALY:349 ALZ:351 AHX:354 AHY:342 AHZ:422
63-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
64-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
65-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:421
66-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:421
67-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
68-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
69-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:341 AHZ:421
70-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
71-ALX:350 ALY:349 ALZ:351 AHX:352 AHY:342 AHZ:422
72-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
73-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
74-ALX:350 ALY:349 ALZ:351 AHX:352 AHY:342 AHZ:422
75-ALX:350 ALY:349 ALZ:351 AHX:352 AHY:342 AHZ:422
76-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
77-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
78-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:421
79-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
80-ALX:350 ALY:350 ALZ:351 AHX:353 AHY:343 AHZ:422
81-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
82-ALX:350 ALY:349 ALZ:351 AHX:353 AHY:342 AHZ:422
Here i cannot use strlen function as it gives me the output 0 as r is set zo zero. without knowing the string length, i cannot proceed to segment it to get the following datas.
Consider for received string 56, I want to store the following value in each iteration in the following the variables
accLowX = 350, accLowY = 349, accLowZ=351
accHighX =353, accHighY = 341, accHighZ =421;
How can i do it?

Answer 1

I would start by creating a string array and put each line in it (with getline maybe?) Then, you can use split function of boost and use a space as a delimiter. Then, put all of these in a temporary array. http://www.cplusplus.com/faq/sequences/strings/split/ -> Boost String Algorithms: Split
After, just use the find (http://www.cplusplus.com/reference/string/string/find/) to identify each parameter and use a switch case for each one. Or, take the array and use it directly, since all position will be the same (ex: [0] = ALX:(Number), [1] = ALY:(Number), etc). Hope this help.

Answer 2

You can use sscanf , something like this -
if(sscanf(s,"%*[^:]:%d %*[^:]:%d %*[^:]:%d %*[^:]:%d %*[^:]:%d %*[^:]:%d"
,&accLowX,&accLowY,&accLowZ,&accHighX,&accHighY,&accHighZ))==6){
// do something
}

Answer 3

After your valuable suggestions, I found this way to solve my problem. This code is inspired by this CodeSource
Modified Code:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BAUDRATE B9600 /* baudrate settings are defined in <asm/termbits.h>, which is included by <termios.h> */
#define MODEMDEVICE "/dev/ttyS1" /* change this definition for the correct port */
#define _POSIX_SOURCE 1 /* POSIX compliant source */
#define FALSE 0
#define TRUE 1
volatile int STOP=FALSE;
int main()
{
int fd,c, res;
struct termios oldtio,newtio;
char buf[255];
char sensorDatas[255];
/* Sensor raw datas */
int accLowX, accLowY, accLowZ;
int accHighX, accHighY, accHighZ;
/*
Open modem device for reading and writing and not as controlling tty
because we don't want to get killed if linenoise sends CTRL-C.
*/
fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY );
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 = BAUDRATE | 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;
/*
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);
/*
terminal settings done, now handle input
In this example, inputting a 'z' at the beginning of a line will
exit the program.
*/
while (STOP==FALSE) { /* loop until we have a terminating condition */
/* read blocks program execution until a line terminating character is
input, even if more than 255 chars are input. If the number
of characters read is smaller than the number of chars available,
subsequent reads will return the remaining chars. res will be set
to the actual number of characters actually read */
res = read(fd,buf,255);
memcpy(sensorDatas, buf, strlen(buf)+1);
buf[res]=0; /* set end of string, so we can printf */
sensorDatas[res]=0;
printf("%s", sensorDatas);
/* Segmentation of Datas received from Arduino */
if(sscanf(sensorDatas,"%*[^:]:%d %*[^:]:%d %*[^:]:%d %*[^:]:%d %*[^:]:%d %*[^:]:%d"
,&accLowX,&accLowY,&accLowZ,&accHighX,&accHighY,&accHighZ)==6) {
// do something
printf( "accLowX : %d\n", accLowX);
printf( "accLowY : %d\n", accLowY);
printf( "accLowZ : %d\n", accLowZ);
}
}
/* restore the old port settings */
tcsetattr(fd,TCSANOW,&oldtio);
}