HMC425A

HMC425A Digital Step Attenuator Linux Driver.

Supported Devices

Evaluation Boards

Description

This is a Linux industrial I/O (Linux Industrial I/O Subsystem) subsystem driver, targeting Digital Step Attenuator IIO devices with gpio interface. 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.

HMC425A 0.5 dB LSB GaAs MMIC 6-BIT DIGITAL POSITIVE CONTROL ATTENUATOR, 2.2 - 8.0 GHz

Source Code

Status

Source	Mainlined?
git	WIP

Files

Function	File
driver	drivers/iio/amplifiers/hmc425a.c
Documentation	Documentation/ABI/testing/sysfs-bus-iio

Devicetree

properties

compatible:

enum:
adi,hmc425a

vcc-supply:

description: digital voltage regulator (see regulator/regulator.txt)
maxItems: 1

ctrl-gpios:

description: Must contain an array of 6 GPIO specifiers, referring to the GPIO pins connected to the control pins V1-V6.
maxItems: 6

required:

compatible
ctrl-gpios

Example

#include <dt-bindings/gpio/gpio.h>

&gpio {
    #address-cells = <1>;
    #size-cells = <0>;
    gpio_hmc425a: hmc425a {
        compatible = "adi,hmc425a";
        ctrl-gpios = <&gpio 40 GPIO_ACTIVE_HIGH>,
        <&gpio 39 GPIO_ACTIVE_HIGH>,
        <&gpio 38 GPIO_ACTIVE_HIGH>,
        <&gpio 37 GPIO_ACTIVE_HIGH>,
        <&gpio 36 GPIO_ACTIVE_HIGH>,
        <&gpio 35 GPIO_ACTIVE_HIGH>;

        vcc-supply = <&foo>;
    };
}

Adding Linux driver support

Configure kernel with make menuconfig (alternatively use make xconfig or make qconfig)

Note

The HMC425A Driver depends on CONFIG_GPIOLIB

Linux Kernel Configuration
    Device Drivers  --->
        <*>     Industrial I/O support --->
            --- Industrial I/O support
                Amplifiers  --->
                    <*> Analog Devices HMC425A DSA

Hardware configuration

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.

root:/> cd /sys/bus/iio/devices/
root:/sys/bus/iio/devices> ls
iio:device0
root:/sys/bus/iio/devices> iio:device0

root:/> ls -l
drwxr-xr-x    2 root     root             0 Jan  1 00:00 .
drwxr-xr-x    3 root     root             0 Jan  1 00:00 ..
-r--r--r--    1 root     root          4096 Jan  1 00:00 dev
-r--r--r--    1 root     root          4096 Jan  1 00:00 name
-rw-r--r--    1 root     root          4096 Jan  1 00:00 out_voltage0_hardwaregain
lrwxrwxrwx    1 root     root             0 Jan  1 00:00 subsystem -> ../../../../../../../../../bus/iio
-rw-r--r--    1 root     root          4096 Jan  1 00:00 uevent

Show device name

root:/> cd /sys/bus/iio/devices/iio\:device0/
root:/> cat name
hmc425a

Set ChannelY Gain

/sys/bus/iio/devices/iio:deviceX/out_voltageY_hardwaregain

Hardware applied gain factor. If shared across all channels, <type>_hardwaregain is used.

root:/> cat out_voltage0_hardwaregain
-31.500000 dB

root:/> echo -10 > out_voltage0_hardwaregain
root:/> cat out_voltage0_hardwaregain
-10.000000 dB