11. ADC Operation Guide¶

This documentDescriptionin CV184x on the platformThrough IIO InterfaceUse SARADC、Channeland sysfs NodeCorrespondence、Voltage andUser space/Kernel spaceOperation Example。

11.1. Preparation¶

1. Kernel Requirements

Use SDK ProvidekernelImage。

2. ADC andChannelDescription

User Through IIO InterfaceAccess 15 12-bit ADC Channel，Refer toVoltage 1.5V。
5 SARADC， 3 12-bit Channel：
- SARADC0～SARADC2： ADC（ 9 ）
- RTC_SARADC0～RTC_SARADC1：RTC ADC（ 6 ）

3. IIO DevicePathandChannelCorrespondence

IIO DevicePathis /sys/bus/iio/devices/iio:device0/， Channel ofRaw ValueNodeas follows：

in_voltage1_raw ～ in_voltage3_raw   # SARADC0
in_voltage4_raw ～ in_voltage6_raw   # SARADC1
in_voltage7_raw ～ in_voltage9_raw   # SARADC2
in_voltage10_raw ～ in_voltage12_raw # RTC_SARADC0
in_voltage13_raw ～ in_voltage15_raw # RTC_SARADC1

4. Voltage

Voltage（mV）= Raw Value × 1500 / 4095

5. PinandFunction

SARADC0 Channel 3 ofPinNameis ADC3；can Default GPIO Function，No need to ：
```
cvi_pinmux -r ADC3
```
RTC_SARADC0 Channel 10 Pin PWR_SEQ3；needSwitch to GPIO Function，for example：
```
cvi_pinmux -r PWR_SEQ3
cvi_pinmux -w PWR_SEQ3/PWR_GPIO_5
```

11.2. Operation Flow¶

Steps 1：

Confirm ADC Channel of Pin（canRefer toSchematic）。
will Voltage to Pin，NoteInputVoltagenot Refer toVoltage 1.5V。
Refer toVoltage 。

Steps 2：PinConfiguration

ADC Channel（SARADC0～2） No need to pinmux。
RTC ADC（RTC_SARADC0/1）orneedwill PinConfigurationis ADC Function，orneed GPIO ，Use cvi_pinmux 。

Steps 3：DataRead

User space：Through /sys/bus/iio/devices/iio:device0/ under of in_voltageN_raw NodeReadRaw Value。

Steps 4：Data

ReadRaw Valueafter，「Voltage（mV）= Raw Value × 1500 / 4095」 isVoltage。
need 、 etc.after 。

11.3. Operation Example¶

11.3.1. Read SARADC0 channel 1 and convert it to voltage¶

# ReadRaw Value
cat /sys/bus/iio/devices/iio:device0/in_voltage1_raw
# ExampleOutput：2048
# Voltage（mV）= 2048 × 1500 / 4095 ≈ 750

Description： Schematicin ADC Channel （If SARADC1～9 on SARADC0～2 of 9 ，PWR_SARADC1～6 RTC_SARADC0/1 of 6 ）， withSchematicis 。

11.3.2. SARADC0 Read example for channel 3 and RTC_SARADC0 channel 10¶

can Table ：willChannel 1.8V or （NoteRaw Value is 4095， Voltage is 1.5V）。

cat /sys/bus/iio/devices/iio:device0/in_voltage3_raw
cat /sys/bus/iio/devices/iio:device0/in_voltage10_raw
#   0

11.3.3. Kernel space ADC Read/writeExample¶

Steps 1：inDevice TreeinisNeed toConfigurationADCChannelofNodeAddADCChannelAttribute

my-adc-consumer@0 {
    compatible = "myco,my-adc-consumer";
    io-channels = <&saradc0 0>;   /* 0 IndicatesChannel 0，  0～14 */
    status = "okay";
};

Steps 2：inDriverin PleaseADCChannelandReadADCValue

struct my_adc_consumer {
    ...
    struct iio_channel *chan;
    ...
};

static int my_adc_consumer_probe(struct platform_device *pdev)
{
    struct my_adc_consumer *priv;
    int ret, val;

    priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
    if (!priv)
        return -ENOMEM;

    /* Get ADC Channel */
    priv->chan = devm_iio_channel_get(&pdev->dev, NULL);
    if (IS_ERR(priv->chan)) {
        dev_err(&pdev->dev, "iio_channel_get failed: %ld\n", PTR_ERR(priv->chan));
        return PTR_ERR(priv->chan);
    }
    /* ReadRaw Value */
    ret = iio_read_channel_raw(priv->chan, &val);
    if (ret < 0) {
        dev_err(&pdev->dev, "read raw failed: %d\n", ret);
        return ret;
    }
    dev_info(&pdev->dev, "ADC raw value: %d\n", val);
    ...
}

11.3.4. User-Space ADC Read/Write Example¶

followingExampleThrough IIO sysfs Read ChannelofRaw Valueand isVoltage（mV）。Channel 1～15 in_voltage1_raw``～``in_voltage15_raw，Voltage ：Voltage（mV）= Raw Value × 1500 / 4095。：./Program <Channel number>，Channel number 1～15。

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

#define ADC_PATH "/sys/bus/iio/devices/iio:device0/"
#define MAX_CHANNELS 15

float read_adc_voltage(int channel)
{
    char path[256];
    char buf[32];
    int fd, raw;
    float voltage;

    if (channel < 1 || channel > MAX_CHANNELS) {
        fprintf(stderr, "Invalid channel: %d (1-%d)\n", channel, MAX_CHANNELS);
        return -1.0;
    }

    snprintf(path, sizeof(path), "%sin_voltage%d_raw", ADC_PATH, channel);

    fd = open(path, O_RDONLY);
    if (fd < 0) {
        fprintf(stderr, "Failed to open %s: %s\n", path, strerror(errno));
        return -1.0;
    }

    memset(buf, 0, sizeof(buf));
    if (read(fd, buf, sizeof(buf) - 1) < 0) {
        fprintf(stderr, "Failed to read %s: %s\n", path, strerror(errno));
        close(fd);
        return -1.0;
    }

    close(fd);

    raw = atoi(buf);
    voltage = (raw * 1500.0) / 4095.0;

    return voltage;
}

int main(int argc, char *argv[])
{
    int channel;
    float voltage;

    if (argc != 2) {
        printf("Usage: %s <channel>\n", argv[0]);
        printf("Channels: 1-15\n");
        printf("  1-3: SARADC0\n");
        printf("  4-6: SARADC1\n");
        printf("  7-9: SARADC2\n");
        printf("  10-12: RTC_SARADC0\n");
        printf("  13-15: RTC_SARADC1\n");
        return 1;
    }

    channel = atoi(argv[1]);
    voltage = read_adc_voltage(channel);

    if (voltage >= 0) {
        printf("Channel %d: %.2f mV (%.3f V)\n",
               channel, voltage, voltage / 1000.0);
    }

    return 0;
}

Run Mode Description

Source Code：willon Code isFile，for example adc_read.c。

Build：inHostoron the target boardUse Tools Build。Example（ is ARM PleaseReplaceisActual Build ）：

#  BuildExample（withActualTools is ）
arm-none-linux-uclibcgnueabihf-gcc -o adc_read adc_read.c -static

Run：inon the target boardExecute， Channel number 1～15。 or andChannelCorrespondence。

./adc_read <Channel number>

Example：

./adc_read 1      # Read SARADC0 Channel 1
./adc_read 10     # Read RTC_SARADC0 Channel 10
./adc_read        #  ：Channels 1-15，and 1-3/4-6/7-9/10-12/13-15 Correspondence

Output：Success ChannelVoltage，If Channel 1: 750.00 mV (0.750 V)；Failure in stderr Output Information。