MRAA on Galileo Gen 2 output

[James_N_1]

Hi,

I'm using the IOTDK Eclipse IDE to compile a C program using the MRAA.  I'm trying to do a basic read to see if the Arduino pins are high or low, this program in particular looks at pin 8 and sends the output to stdout. I'm basing my program off of this: http://iotdk.intel.com/docs/master/mraa/gpio_8h.html

#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include "mraa/gpio.h"

int main(int argc, char **argv)
{
    mraa_gpio_context gpio8;
    gpio8=mraa_gpio_init(8);
    mraa_gpio_dir(gpio8, MRAA_GPIO_IN);
    for (;;) {
        fprintf(stdout, "The value of pin 8 is: %d\n", gpio8);
        sleep(1);
    }

I'm getting the following output:

The value of pin 8 is: 143212968
The value of pin 8 is: 143212968

... and so on. What does this integer mean, and how do I determine if this is high or low? Thanks!

[Matthias_H_Intel]

not answering your question but in general:

which platform are you on?

have you latest MRAA running on your target?

[James_N_1]

I'm on the galileo gen 2 running the latest iotdk image.  I've done a board firmware upgrade via the arduino console (not related im guessing) and also run opkg update and opkg upgrade, so not really sure what version of mraa.  I would just use the arduino ide, but I'd like to export the data into a JSON and send that out, so I figured a C or python script would do the trick best?

Thanks for the interest,

Jim

[Brian_B_Intel · Accepted solution]

Hi Jim. 

That integer looks to be the memory location of the gpio8 structure. I think you need to read the pin value with:

fprintf(stdout, "The value of pin 8 is %d\n", mraa_gpio_read(gpio8));

See http://iotdk.intel.com/docs/master/mraa/gpio_8h.html

Brian

[James_N_1]

That makes a lot of sense, I should've seen that lol.

That's definitely what was wrong with it, I simply changed that line and voila. Thanks, Brian!