I am working on a project that involves reading data from an Arduino Uno over serial port. In Arduino IDE, I observe that I am successfully printing values over the serial port in the following format:
Serial.print(x, DEC);
Serial.print(' ');
Serial.print(y, DEC);
Serial.print(' ');
Serial.println(z, DEC);
eg:
2 4 -41
4 8 -32
10 5 -50
...etc.
Then, I have a program written in C using XCode to read these values as float data types. However, upon running the program in terminal, the program appears to be stuck (no values are read, and I must use ctrl+C to exit).
Any ideas what I might be doing wrong? Below is my code. As of now, I am just using a for loop to test whether I am actually reading in these values. Let me know if you need more information. Thanks for your help.
#include <stdio.h>
#include <ApplicationServices/ApplicationServices.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
// buffer for data
float buffer[100];
int main(int argc, const char* argv[])
{
// open serial port
int port;
port = open("/dev/tty.usbmodem1411", O_RDONLY);
if (port == -1)
{
printf("Unable to open serial port.");
}
// testing read of data
fcntl(port, F_SETFL, FNDELAY);
for (int i = 0; i < 10; i++)
{
read(port, buffer, 12);
printf("%.2f %.2f %.2f\n", buffer[3*i], buffer[3*i+1], buffer[3*i+2]);
}
// close serial port
close(port);
return 0;
}
What are you attempting with
read(port, buffer, 12);
printf("%.2f %.2f %.2f\n", buffer[3*i], buffer[3*i+1], buffer[3*i+2]);
??? buffer
will contain string data, like following (not floating points):
{'2', ' ', '4', '0', ' ', '-', '4', '1', 0x0D, 0x0A, '4', ' ', '8'}
//0 1 2 2 3 4 5 6 7 8 9 10 11
Your first mistake is reading exactly 12 bytes - each line may have different number of bytes. Second mistake is trying to format a char
as a float
. Even printf
may get invalid data as it expects 3 floats and you are supllying 3 chars.
So, you need to parse your input data! Some direction:
#include <stdio.h>
float input[3];
int main(int argc, const char* argv[]) {
FILE *port;
port=fopen("/dev/tty.usbmodem1411", "r"); //fopen instead, in order to use formatted I/O functions
if (port==NULL) {
printf("Unable to open serial port.");
return 1; //MUST terminate execution here!
}
for (int i = 0; i < 10; i++) {
fscanf(, "%f %f %f", &input[0], &input[1], &input[2]);
printf("%.2f %.2f %.2f\n", input[0], input[1], input[2]);
}
fclose(port);
return 0;
}
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