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sunychip-RK3288 开发板上的 AD 接口分为：高速 ADC 流接口 (High-speed ADC Stream Interface)、温度传感器 (Temperature Sensor)、 逐次逼近ADC (Successive Approximation Register)。本文主要介绍 ADC 的基本配置方法。内核采用工业 I/O 子系统来控制 ADC， 该子系统主要为 AD 转换或者 DA 转换的传感器设计。其相关数据结构以及配置方法如下：
struct iio_channel {
struct iio_dev *indio_dev;//工业 I/O设备
const struct iio_chan_spec *channel;//I/O通道
void *data;};struct iio_dev {
int id;
int modes;
int currentmode;
struct device dev;
struct iio_event_interface *event_interface;
struct iio_buffer *buffer;
struct list_head buffer_list;
int scan_bytes;
struct mutex mlock;
const unsigned long *available_scan_masks;
unsigned masklength;
const unsigned long *active_scan_mask;
bool scan_timestamp;
unsigned scan_index_timestamp;
struct iio_trigger *trig;
struct iio_poll_func *pollfunc;
struct iio_chan_spec const *channels;
int num_channels;
struct list_head channel_attr_list;
struct attribute_group chan_attr_group;
const char *name;
const struct iio_info *info;
struct mutex info_exist_lock;
const struct iio_buffer_setup_ops *setup_ops;
struct cdev chrdev;
#define IIO_MAX_GROUPS 6
const struct attribute_group *groups[IIO_MAX_GROUPS + 1];
int groupcounter;
unsigned long flags;
#if defined(CONFIG_DEBUG_FS)
struct dentry *debugfs_dentry;
unsigned cached_reg_addr;
#endif};struct iio_chan_spec {
enum iio_chan_type type; //描述通道类型
int channel; //通道号
int channel2; //通道号
unsigned long address; //通道地址
int scan_index;
struct {
char sign;
u8 realbits;
u8 storagebits;
u8 shift;
enum iio_endian endianness;
} scan_type;
long info_mask;
long info_mask_separate;
long info_mask_shared_by_type;
long event_mask;
const struct iio_chan_spec_ext_info *ext_info;
const char *extend_name;
const char *datasheet_name;
unsigned modified:1;
unsigned indexed:1;
unsigned output:1;
unsigned differential:1;};ADC的 DTS 节点在 kernel/arch/arm/boot/dts/rk3288.dtsi 文件中定义，如下所示：
adc: adc@ff100000 {
compatible = "rockchip,saradc";
reg = <0xff100000 0x100>;
interrupts = <GIC_SPI 36 IRQ_TYPE_LEVEL_HIGH>;
#io-channel-cells = <1>;
io-channel-ranges;rockchip,adc-vref = <1800>;
clock-frequency = <1000000>;
clocks = <&clk_saradc>, <&clk_gates7 1>;
clock-names = "saradc", "pclk_saradc";
status = "disabled";
};用户只需在 firefly-rk3288.dts 文件中添加通道定义，并将其 status 改为 “okay” 即可：
&adc {
status = "okay";
adc_test{
compatible = "rockchip,adc_test";
io-channels = <&adc 0>;
};};在驱动文件中定义 of_device_id 结构体数组：
static const struct of_device_id of_XXX_match[] = {
{ .compatible = "rockchip,adc_test" },
{ /* Sentinel */ }};将该结构体数组填充到要使用 ADC 的 platform_driver 中。
static struct platform_driver XXX_driver = {
.probe = ...,
.remove = ...,
.driver = {
.name = "..",
.owner = THIS_MODULE,
#ifdef CONFIG_OF
.of_match_table = of_XXX_match,
#endif
}, };struct iio_channel *chan; //定义 IIO 通道结构体chan = iio_channel_get(&pdev->dev, NULL); //获取 IIO 通道结构体注：iio_channel_get 通过 probe 函数传进来的参数 pdev 获取 IIO 通道结构体，probe 函数如下：
static int XXX_probe(struct platform_device *pdev);int val,ret;ret = iio_read_channel_raw(chan, &val);调用 iio_read_channel_raw 函数读取 AD 采集的原始数据并存入 val 中。
使用标准电压将 AD 转换的值转换为用户所需要的电压值。其计算公式如下：
Vref / (2^n-1) = Vresult / raw注： Vref 为标准电压 n 为 AD 转换的位数 Vresult 为用户所需要的采集电压 raw 为 AD 采集的原始数据 例如，标准电压为 1.8V，AD 采集位数为 10 位，AD 采集到的原始数据为 568，则：
Vresult = (1800mv * 568) / 1023;struct iio_channel *iio_channel_get(struct device *dev, const char *consumer_channel);void iio_channel_release(struct iio_channel *chan);int iio_read_channel_raw(struct iio_channel *chan, int *val);免责声明：本站发布的内容（图片、视频和文字）以原创、转载和分享为主，文章观点不代表本网站立场，如果涉及侵权请联系站长邮箱：is@yisu.com进行举报，并提供相关证据，一经查实，将立刻删除涉嫌侵权内容。