Linux中的libiio编程实践

    开发板：Omapl138

    AD模块：AD7606

1 交叉编译libiio

    关于libiio的交叉编译，见《Linux中交叉编译libiio》。

2 简单实例

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

/*
 * 功 能: 通道属性检索
 * 参 数: chn 	—— AD 通道
 * 		  attr 	—— 需要检索的属性
 * 返 回: true  —— AD通道存在属性attr
 * 		  false —— AD通道不存在属性attr
 */
static bool channel_has_attr(struct iio_channel *chn, const char *attr)
{
	unsigned int i, nb = iio_channel_get_attrs_count(chn);
	for (i = 0; i < nb; i++)
		// printf("channel attr = %s\n", iio_channel_get_attr(chn, i));
		if (!strcmp(attr, iio_channel_get_attr(chn, i)))
			return true;
	return false;
}
/*
 * 功 能: 获取通道chan的采样值
 * 参 数: chn —— AD 通道
 * 返 回: chn 通道的采样值
 */
static double get_channel_value(struct iio_channel *chn)
{
	char buf[1024];
	double val;

	if (channel_has_attr(chn, "processed")) {
		iio_channel_attr_read(chn, "processed", buf, sizeof(buf));
		val = strtod(buf, NULL);
	} else {
		iio_channel_attr_read(chn, "raw", buf, sizeof(buf));
		val = strtod(buf, NULL);

		if (channel_has_attr(chn, "offset")) {
			iio_channel_attr_read(chn, "offset", buf, sizeof(buf));
			val += strtod(buf, NULL);
		}

		if (channel_has_attr(chn, "scale")) {
			iio_channel_attr_read(chn, "scale", buf, sizeof(buf));
			val *= strtod(buf, NULL);
		}
	}

	val = val * 5 / 32768.0;
	return val;
}

int main(void)
{
	struct iio_context *ctx;
	unsigned int i, nb_devices;
	unsigned int nb_channels;
	double channel_value;
	struct iio_device *dev;
	struct iio_channel *chn;

	// create context
	ctx = iio_create_local_context();
	if ( !ctx) {
		printf("create context failed\n");
		exit(0);
	}

	// get device count
	nb_devices = iio_context_get_devices_count(ctx);
	
	// get device name
	dev = iio_context_get_device(ctx, 0);

	nb_channels = iio_device_get_channels_count(dev);
	
	chn = iio_device_get_channel(dev, 0);

	printf("channel_value:\n");
	for (i = 0; i < 100000; i++) {
		channel_value = get_channel_value(chn);
		printf("%.2f\n", channel_value);
		sleep(1);
	}
	
	iio_context_destroy(ctx);

	return 0;
}

参考资料

[1]What is libiio?

[2]libiio_Main Page

[3]About libiio

[4]iio-trig-sysfs driver

[5]IIO Command Server

[6][RFC] LIBIIO

[7]libiio buffering

[8]How to Get Analog Input on the BeagleBone Black

[9]How to use the Linux Industrial IO (IIO) interface

[10]AM335x ADC Driver's Guide

[11]AD7606: Data capture by setting sampling frequency & buffer mode

[12]IIO, a new kernel subsystem

[13]Why this program can't receive the right data?

[14]linux-3.2.20/drivers/staging/iio/industrialio-buffer.c

[15]Linux Core ADC User's Guide

[16]am335x adc调试