Re: BBB IIO ADC access not working

[Michael Welling <mwelling@ieee.org>]

On Wed, Aug 19, 2015 at 02:34:39PM -0700, Greg Wilson-Lindberg wrote:
> 
> So, in that case, can I just open it once and leave it open?

Yes.

> Is it reading from a buffer, or is it reading what is current in the ADC? 

It is the current reading.

> Can I just set up a timer to get readings to average then?

Sure.

Here are some helper functions:

int iio_adc_open_channel(int dev_num, int chan_num)
{
	char filename[255];

	sprintf(filename, "/sys/bus/iio/devices/iio:device%d/in_voltage%d_raw",
			dev_num, chan_num);

	return open(filename, O_RDONLY);
}

int iio_adc_read_channel(int fd)
{
	int count;
	char buffer[255];
	int value = -1;

	lseek(fd,0,SEEK_SET);

	count = read(fd, buffer, 255);

	if (count > 0)
		value = strtoul(buffer, NULL, 10);

	return value;
}

Example usage:

int fd;
.
.

fd = iio_adc_open_channel(0, 4);
.
.

while (1)
{
	printf("ADC = %x\n", iio_adc_read_channel(fd));
}