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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

ad5592r_eval.jpg

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
resources/tools-software/linux-drivers/iio-dac/ad5593r.1456159942.txt.gz · Last modified: 22 Feb 2016 17:52 by Michael Hennerich