It's been a while since I've written anything in C++, but I notice you're
not doing any error checking on your filestream. For instance check out the
very simply code listing I demonstrate here ( in C ).
http://www.embeddedhobbyist.com/2015/10/beaglebone-black-adc/
Notice that I'm checking if length is -1, and if so, moving code execution
back up to the top of the loop. Using continue. You should be doing
something similar( whatever filestream allows ). Also, I've not idea how
filestream works in Linux, but if you're opening a new file descriptor
every function call, you'll want to refactor that out. e.g. you get your
file descriptor only once when the executable is first run, and then
operate off that.
Another thing that you have not really asked about but deserves mention.
You're declaring 2 int's and two floats every program loop. You'll want to
fix that . . .
On Fri, Jan 1, 2016 at 9:26 PM, Sunny Sharma <sunnysharm...@gmail.com>
wrote:
> Hi friends,
>
> I am trying to voltage values from 2 analog sensors which are connected to
> pins AIN0 and AIN1 using C++. I have taken Derek Molloy's code for reading
> one voltage value and edited it to add a second pin to read values from. *The
> code is as follows: *
>
> #include<iostream>
> #include<fstream>
> #include<string>
> #include<sstream>
> #include<cmath>
> using namespace std;
>
> #define LDR_PATH "/sys/bus/iio/devices/iio:device0/in_voltage"
>
> int readAnalog(int number){
>
> stringstream ss;
>
> ss << LDR_PATH << number << "_raw";
>
> fstream fs;
>
> fs.open(ss.str().c_str(), fstream::in);
>
> fs >> number;
>
> fs.close();
>
> return number;
>
> }
>
> int main(int argc, char* argv[]){
>
> cout << "Starting the IR distance sensor program:" << endl;
>
> while(1) {
>
> int value0 = readAnalog(0);
> int value1 = readAnalog(1);
> float V0 = ((float)value0 / 4096) * 1.8;
> float V1 = ((float)value1 / 4096) * 1.8;
>
> cout << "Sensor0 is: " << V0 << " Sensor1 is: " << V1 << '\r' <<
> flush;
>
> usleep(100000);
>
> }
>
> return 0;
> }
>
> However, when I run this code, after 10-15 successful iterations, *I
> receive this error message: *
>
> terminate called after throwing an instance of 'std::ios_base::failure'
> what(): basic_filebuf::underflow error reading the file
> Aborted
>
> I am not sure as to why I am receiving this error, or really what this
> error message even means. My guess it is some access error when trying to
> read the pin value.
>
> The Adafruit BBIO python library actually found a work around this issue
> in C, but I'm not sure how I can extrapolate this to C++ (see:
> https://github.com/adafruit/adafruit-beaglebone-io-python/blob/master/source/c_adc.c
> )
>
> If anyone has any insight or help they could offer, that would be very
> helpful!
>
> Thanks
>
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