This version is outdated by a newer approved version.
This version (23 Feb 2016 13:27) is a draft.
Approvals: 0/1The Previously approved version (22 Feb 2016 17:52) is available.
This version (23 Feb 2016 13:27) is a draft.Approvals: 0/1The Previously approved version (22 Feb 2016 17:52) is available.
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Table of Contents
AD5593R IIO DAC/ADC Linux Driver
Supported Devices
Reference Circuits
Evaluation Boards
Description
The AD5593R have eight I/Ox pins (I/O0 to I/O7) that can be independently configured as digital-to-analog converter (DAC) outputs, analog-to-digital converter (ADC) inputs, digital outputs, or digital inputs.
When an I/Ox pin is configured as an analog output, it is driven by a 12-bit DAC. The output range of the DAC is 0 V to VREF or 0 V to 2 × VREF.
When an I/Ox pin is configured as an analog input, it is connected to a 12-bit ADC via an analog multiplexer. The input range of the ADC is 0 V to VREF or 0 V to 2 × VREF. The ADC has a total throughput rate of 400 kSPS.
The I/Ox pins can also be configured as digital, general-purpose input or output (GPIO) pins. The state of the GPIO pins can be set or read back by accessing the GPIO write data register or the GPIO read configuration register, respectively, via an I2C write or read operation.
The AD5593R have an integrated 2.5 V, 25 ppm/°C reference, which is turned off by default, and an integrated temperature indicator, which gives an indication of the die temperature. The temperature value is read back as part of an ADC read sequence.
Hardware configuration
Adding Linux driver support
Enabling the driver
Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)
The AD5593R Driver depends on CONFIG_I2C
Linux Kernel Configuration
Device Drivers --->
...
<*> Industrial I/O support --->
--- Industrial I/O support
...
Digital to analog converters --->
...
<*> Analog Devices AD5593R ADC/DAC driver
...
...
...
Adding a device tree entry
Required properties
- compatible: Must be one of:
- “adi,ad5593r”
- reg: I2C address of the chip (generally 0x10).
- channel-modes: An array of eight 8-bit values (one per channel) describing the mode of each channel. Macros specifying the valid values can be found in <dt-bindings/iio/adi,ad5592r.h>. The following values are currently supported:
- CH_MODE_ADC (the pin is ADC input)
- CH_MODE_DAC (the pin is DAC output)
- CH_MODE_DAC_AND_ADC (the pin is DAC output but can be monitored by an ADC)
- CH_MODE_UNUSED_PULL_DOWN (the pin is pulled down)
- CH_MODE_UNUSED_OUT_LOW (the pin is output low)
- CH_MODE_UNUSED_OUT_HIGH (the pin is output high)
- CH_MODE_UNUSED_OUT_TRISTATE (the pin is tristated output)
- CH_MODE_GPIO (the pin is registered with GPIOLIB)
- CH_MODE_GPIO_OPEN_DRAIN (the pin is configured open drain and registered with GPIOLIB)
Optional properties
- vref-supply: Phandle to the external reference voltage supply. This should only be set if there is an external reference voltage connected to the VREF pin. If the property is not set the internal 2.5V reference is used.
- reset-gpios: GPIO spec for the RESET pin. If specified, it will be asserted during driver probe.
Device tree example
The following example instanciates the ad5593r driver for a AD5593R device connected on a I2C bus. It sets the I/O0 port as a DAC, the I/O1 port as ADC. I/O2 and I/O3 are configured for primary function DAC the additional ADC can measure the voltage being provided by the DAC. This feature can monitor the output voltage to detect short circuits or overload conditions. I/O4 is connected to the ground with a pull-down resistor. The other I/Os are registered with the Linux GPIO subsystem.
#include <dt-bindings/iio/adi,ad5592r.h>
vref: regulator-vref {
compatible = "regulator-fixed";
regulator-name = "vref-ad559x";
regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
regulator-always-on;
};
&i2c0 {
status = "okay";
clock-frequency = <400000>;
ad5593r@10 {
compatible = "adi,ad5593r";
reg = <0x10>;
channel-modes = /bits/ 8 <
CH_MODE_DAC
CH_MODE_ADC
CH_MODE_DAC_AND_ADC
CH_MODE_DAC_AND_ADC
CH_MODE_UNUSED_PULL_DOWN
CH_MODE_GPIO
CH_MODE_GPIO
CH_MODE_GPIO
>;
vref-supply = <&vref>; /* optional */
reset-gpios = <&gpio0 86 0>; /* optional */
};
};
Driver testing
If the driver correctly detected the device, the “iio_info” program should inform us about the available channels:
root@linaro-ubuntu-desktop:~# iio_info
IIO context created: local
IIO context has 3 devices:
iio:device2: ad5593r
7 channels found:
voltage0: (output)
3 channel-specific attributes found:
attr 0: raw value: 0
attr 1: scale_available value: 0.732421875 1.464843750
attr 2: scale value: 0.732421875
voltage2: (output)
3 channel-specific attributes found:
attr 0: raw value: 0
attr 1: scale_available value: 0.732421875 1.464843750
attr 2: scale value: 0.732421875
voltage3: (output)
3 channel-specific attributes found:
attr 0: raw value: 0
attr 1: scale_available value: 0.732421875 1.464843750
attr 2: scale value: 0.732421875
voltage1: (input)
3 channel-specific attributes found:
attr 0: raw value: 0
attr 1: scale value: 0.732421875
attr 2: scale_available value: 0.732421875 1.464843750
voltage2: (input)
3 channel-specific attributes found:
attr 0: raw value: 1
attr 1: scale value: 0.732421875
attr 2: scale_available value: 0.732421875 1.464843750
voltage3: (input)
3 channel-specific attributes found:
attr 0: raw value: 0
attr 1: scale value: 0.732421875
attr 2: scale_available value: 0.732421875 1.464843750
temp: (input)
3 channel-specific attributes found:
attr 0: offset value: -628
attr 1: raw value: 680
attr 2: scale value: 452.147700000
GPIO Testing
The GPIO sysfs interface allows users to manipulate any GPIO from userspace. Userspace utilizes a sysfs control interface to dynamically request and release individual GPIOs. Once a GPIO has been requested, writing to the newly created path allows you to control the direction and the data while reading from it returns the GPIO data (which usually corresponds to a 0 or 1 which represents the signal level).
For more information see also here: GPIO Kernel Documentation
root@linaro-ubuntu-desktop:~# cd /sys/class/gpio/ root@linaro-ubuntu-desktop:/sys/class/gpio# ls export gpiochip890 gpiochip898 gpiochip906 unexport root@linaro-ubuntu-desktop:/sys/class/gpio# cd gpiochip890 root@linaro-ubuntu-desktop:/sys/class/gpio/gpiochip890# ls -al total 0 drwxr-xr-x 3 root root 0 Jan 1 1970 . drwxr-xr-x 3 root root 0 Jan 1 1970 .. -r--r--r-- 1 root root 4096 Feb 23 08:06 base lrwxrwxrwx 1 root root 0 Feb 23 08:06 device -> ../../../0-0010 -r--r--r-- 1 root root 4096 Feb 23 08:06 label -r--r--r-- 1 root root 4096 Feb 23 08:06 ngpio drwxr-xr-x 2 root root 0 Feb 23 08:06 power lrwxrwxrwx 1 root root 0 Jan 1 1970 subsystem -> ../../../../../../../../class/gpio -rw-r--r-- 1 root root 4096 Jan 1 1970 uevent root@linaro-ubuntu-desktop:/sys/class/gpio/gpiochip890# grep "" * base:890 label:0-0010 ngpio:8 root@linaro-ubuntu-desktop:/sys/class/gpio/gpiochip890# cd .. root@linaro-ubuntu-desktop:/sys/class/gpio# echo 897 > export root@linaro-ubuntu-desktop:/sys/class/gpio# cd gpio897/ root@linaro-ubuntu-desktop:/sys/class/gpio/gpio897# ls -al total 0 drwxr-xr-x 3 root root 0 Feb 23 08:06 . drwxr-xr-x 4 root root 0 Feb 23 08:06 .. -rw-r--r-- 1 root root 4096 Feb 23 08:06 active_low lrwxrwxrwx 1 root root 0 Feb 23 08:06 device -> ../../../0-0010 -rw-r--r-- 1 root root 4096 Feb 23 08:06 direction drwxr-xr-x 2 root root 0 Feb 23 08:06 power lrwxrwxrwx 1 root root 0 Feb 23 08:06 subsystem -> ../../../../../../../../class/gpio -rw-r--r-- 1 root root 4096 Feb 23 08:06 uevent -rw-r--r-- 1 root root 4096 Feb 23 08:06 value root@linaro-ubuntu-desktop:/sys/class/gpio/gpio897# cat direction in root@linaro-ubuntu-desktop:/sys/class/gpio/gpio897# cat value 0 root@linaro-ubuntu-desktop:/sys/class/gpio/gpio897# echo low > direction root@linaro-ubuntu-desktop:/sys/class/gpio/gpio897# cat direction out root@linaro-ubuntu-desktop:/sys/class/gpio/gpio897# cat value 0 root@linaro-ubuntu-desktop:/sys/class/gpio/gpio897# echo high > direction root@linaro-ubuntu-desktop:/sys/class/gpio/gpio897# cat value 1
resources/tools-software/linux-drivers/iio-dac/ad5593r.1456230427.txt.gz · Last modified: 23 Feb 2016 13:27 by Michael Hennerich