AD4170

AD4170 24-Bit Sigma-Delta ADC with Integrated PGA Linux Driver.

Supported Devices

This driver supports the

AD4170

Evaluation Boards

EVAL-AD4170

Description

This is a Linux industrial I/O (Linux Industrial I/O Subsystem) subsystem driver, targeting single channel serial interface ADCs. The industrial I/O subsystem provides a unified framework for drivers for many different types of converters and sensors using a number of different physical interfaces (i2c, spi, etc). See Linux Industrial I/O Subsystem for more information.

Status

Source
ADI Linux repository’s branch dev_ad4170

Files

Function	File
driver	drivers/iio/adc/ad4170.c]]

Driver testing

Each and every IIO device, typically a hardware chip, has a device folder under /sys/bus/iio/devices/iio:deviceX. Where X is the IIO index of the device. Under every of these directory folders reside a set of files, depending on the characteristics and features of the hardware device in question. These files are consistently generalized and documented in the IIO ABI documentation. In order to determine which IIO deviceX corresponds to which hardware device, the user can read the name file /sys/bus/iio/devices/iio:deviceX/name. In case the sequence in which the iio device drivers are loaded/registered is constant, the numbering is constant and may be known in advance.

Tip

An example program which uses the interface can be found here:

IIO Oscilloscope

root@analog:~# cd /sys/bus/iio/devices/

root@analog:/sys/bus/iio/devices# ls

iio:device0  trigger0

root@analog:/sys/bus/iio/devices# cd iio\:device0

root@analog:/sys/bus/iio/devices/iio:device0# ls -l

total 0

drwxr-xr-x 2 root root    0 Sep 13 08:09 buffer
-r--r--r-- 1 root root 4096 Sep 13 08:09 dev
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage0-voltage24_calibbias
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage0-voltage24_calibscale
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage0-voltage24_filter_type
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage0-voltage24_offset
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage0-voltage24_raw
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage0-voltage24_sampling_frequency
-r--r--r-- 1 root root 4096 Sep 13 08:09 in_voltage0-voltage24_sampling_frequency_available
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage0-voltage24_scale
-r--r--r-- 1 root root 4096 Sep 13 08:09 in_voltage0-voltage24_scale_available
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage29-voltage24_calibbias
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage29-voltage24_calibscale
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage29-voltage24_filter_type
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage29-voltage24_offset
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage29-voltage24_raw
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage29-voltage24_sampling_frequency
-r--r--r-- 1 root root 4096 Sep 13 08:09 in_voltage29-voltage24_sampling_frequency_available
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage29-voltage24_scale
-r--r--r-- 1 root root 4096 Sep 13 08:09 in_voltage29-voltage24_scale_available
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage3-voltage4_calibbias
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage3-voltage4_calibscale
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage3-voltage4_filter_type
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage3-voltage4_offset
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage3-voltage4_raw
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage3-voltage4_sampling_frequency
-r--r--r-- 1 root root 4096 Sep 13 08:09 in_voltage3-voltage4_sampling_frequency_available
-rw-r--r-- 1 root root 4096 Sep 13 08:09 in_voltage3-voltage4_scale
-r--r--r-- 1 root root 4096 Sep 13 08:09 in_voltage3-voltage4_scale_available
-r--r--r-- 1 root root 4096 Sep 13 08:09 in_voltage-voltage_filter_type_available
-r--r--r-- 1 root root 4096 Sep 13 08:09 name
lrwxrwxrwx 1 root root    0 Sep 13 08:09 of_node -> ../../../../../../../../firmware/devicetree/base/soc/spi@7e204000/ad4170@0
drwxr-xr-x 2 root root    0 Sep 13 08:09 power
drwxr-xr-x 2 root root    0 Sep 13 08:09 scan_elements
lrwxrwxrwx 1 root root    0 Sep 13 08:09 subsystem -> ../../../../../../../../bus/iio
drwxr-xr-x 2 root root    0 Sep 13 08:09 trigger
-rw-r--r-- 1 root root 4096 Sep 13 08:09 uevent

Show device name

root:/sys/bus/iio/devices/iio:device0> cat name
ad4170

Show channel scale, offset, sampling_frequency, calibbias, calibscale

Description:
Scale, offset, calibbias, calibscale, sampling frequency for the in_voltagex_voltagey channel
0.000149011
root:/sys/bus/iio/devices/iio:device0> cat in_voltage29-voltage24_offset
0
root:/sys/bus/iio/devices/iio:device0> cat in_voltage29-voltage24_raw
16777216
root:/sys/bus/iio/devices/iio:device0> cat in_voltage29-voltage24_calibbias
0
root:/sys/bus/iio/devices/iio:device0> cat in_voltage29-voltage24_calibscale
0
root:/sys/bus/iio/devices/iio:device0> cat in_voltage29-voltage24_sampling_frequency
125000.000000000

Description: Channel Ainp29-Ainm24 is configured as unipolar, with a gain of 1 U = //in_voltage29-voltage24_raw * in_voltage29-voltage24_scale - in_voltage29-voltage24_offset // = 16777216* 0.000149011 - 0 = 2499.98 mV

Show channel scale_available and sampling_frequency_available

Description:
Scales and sampling rates to be applied to the channel.

root:/sys/bus/iio/devices/iio:device0> cat in_voltage29-voltage24_scale_available
0.000149011 0.000074505 0.000037252 0.000018626 0.000009313 0.000004656 0.000002328 0.000001164 0.000298023 0.000149011
root:/sys/bus/iio/devices/iio:device0> cat in_voltage29-voltage24_sampling_frequency_available
[7.629860220 15.259720441 125000.000000000]

Show filter_type_available

root:/sys/bus/iio/devices/iio:device0> cat in_voltage-voltage_filter_type_available
sinc5+avg sinc5 sinc3

Device Tree

ad4170@0 {
            compatible = "adi,ad4170";
            reg = <0>;
            avdd-supply = <&avdd>;
            #address-cells = <1>;
            #size-cells = <0>;

            spi-max-frequency = <5000000>;
            interrupts = <25 IRQ_TYPE_EDGE_FALLING>;
            interrupt-parent = <&gpio>;
            interrupt-names = "adc_rdy";
            adi,dig-aux1-function = "rdy";

            //adi,gpio0-power-down-switch;
            //adi,gpio1-power-down-switch;

            channel@0 {
                reg = <0>;

                adi,reference-select = <AD4170_REFIN_REFOUT>;

                / REFOUT, DGND /
                diff-channels = <29 24>;
                adi,chop-iexc = <AD4170_CHOP_IEXC_OFF>;
                adi,chop-adc = <AD4170_CHOP_ACX_2PIN>;
            };

            channel@1 {
                reg = <1>;

                adi,reference-select = <2>;

                / AIN0, DGND  /
                diff-channels = <0 24>;
                bipolar;
            };

            channel@2 {
                reg = <2>;

                adi,reference-select = <2>;

                / AIN3+, AIN4-  /
                diff-channels = <3 4>;
                bipolar;
            };
}

The adi,gpio0-power-down-switch and adi,gpio1-power-down-switch properties enable the power down switches on GPIO0 and GPIO1 repectively. AC excitation is controlled via adi,chop_iexc and adi,chop_adc properties and can use 2 or 4 gpio pins.