This version (19 Jan 2018 10:13) was approved by Alexandru Ardelean.The Previously approved version (05 Dec 2017 14:17) is available.
Table of Contents
AD5592R IIO DAC/ADC Linux Driver
Supported Devices
Reference Circuits
Evaluation Boards
Description
The AD5592R/AD5592R-1 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 a serial peripheral interface (SPI) write or read operation.
The AD5592R/AD5592R-1 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.
Source Code
Status
Files
| Function | File |
|---|---|
| driver | drivers/iio/dac/ad5592r-base.c |
| include | drivers/iio/dac/ad5592r-base.h |
| driver | drivers/iio/dac/ad5592r.c |
| include | include/dt-bindings/iio/adi,ad5592r.h |
| Documentation | Documentation/devicetree/bindings/iio/dac/ad5592r.txt |
Hardware configuration
Adding Linux driver support
Enabling the driver
Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)
The AD5592R Driver depends on CONFIG_SPI_MASTER
Linux Kernel Configuration
Device Drivers --->
...
<*> Industrial I/O support --->
--- Industrial I/O support
...
Digital to analog converters --->
...
<*> Analog Devices AD5592R ADC/DAC driver
...
...
...
Adding a device tree entry
Required properties
- compatible: Must be one of:
- “adi,ad5592r”
- reg: SPI chip select number for the device
- spi-max-frequency: Max SPI frequency to use (< 30000000)
- spi-cpol: The AD5592R requires inverse clock polarity (CPOL) mode
- #address-cells: Should be 1.
- #size-cells: Should be 0.
- channel nodes:
- Each child node represents one channel and has the following
- Required properties:
- reg: Pin on which this channel is connected to.
- adi,mode: Mode or function of this channel. Macros specifying the valid values can be found in <dt-bindings/iio/adi,ad5592r.h>. The following values are currently supported:
- CH_MODE_UNUSED (the pin is unused)
- 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, since there is no disadvantage this this should be considered as the preferred DAC mode)
- CH_MODE_GPIO (the pin is registered with GPIOLIB)
- Optional properties:
- adi,off-state: State of this channel when unused or the device is removed. Macros specifying the valid values can be found in <dt-bindings/iio/adi,ad5592r.h>.
- CH_OFFSTATE_PULLDOWN (the pin is pulled down)
- CH_OFFSTATE_OUT_LOW (the pin is output low)
- CH_OFFSTATE_OUT_HIGH (the pin is output high)
- CH_OFFSTATE_OUT_TRISTATE (the pin is tristated output)
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.
- gpio-controller: Marks the device node as a GPIO controller.
- #gpio-cells: Should be 2. The first cell is the GPIO number and the second cell specifies GPIO flags, as defined in <dt-bindings/gpio/gpio.h>.
Device tree example
The following example instanciates the ad5592r driver for a AD5592R device connected on the SPI bus to the chip-select line 0. 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;
};
ad5592r@0 {
#size-cells = <0>;
#address-cells = <1>;
#gpio-cells = <2>;
compatible = "adi,ad5592r";
reg = <0>;
spi-max-frequency = <1000000>;
spi-cpol;
vref-supply = <&vref>; /* optional */
reset-gpios = <&gpio0 86 0>; /* optional */
gpio-controller;
channel@0 {
reg = <0>;
adi,mode = <CH_MODE_DAC>;
};
channel@1 {
reg = <1>;
adi,mode = <CH_MODE_ADC>;
};
channel@2 {
reg = <2>;
adi,mode = <CH_MODE_DAC_AND_ADC>;
};
channel@3 {
reg = <3>;
adi,mode = <CH_MODE_DAC_AND_ADC>;
adi,off-state = <CH_OFFSTATE_PULLDOWN>;
};
channel@4 {
reg = <4>;
adi,mode = <CH_MODE_UNUSED>;
adi,off-state = <CH_OFFSTATE_PULLDOWN>;
};
channel@5 {
reg = <5>;
adi,mode = <CH_MODE_GPIO>;
adi,off-state = <CH_OFFSTATE_PULLDOWN>;
};
channel@6 {
reg = <6>;
adi,mode = <CH_MODE_GPIO>;
adi,off-state = <CH_OFFSTATE_PULLDOWN>;
};
channel@7 {
reg = <7>;
adi,mode = <CH_MODE_GPIO>;
adi,off-state = <CH_OFFSTATE_PULLDOWN>;
};
};
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
IIO sysfs interface
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2# ls -al total 0 drwxr-xr-x 3 root root 0 Jan 1 1970 . drwxr-xr-x 5 root root 0 Jan 1 1970 .. -rw-rw-rw- 1 root root 4096 Jan 1 1970 dev -rw-rw-rw- 1 root root 4096 Jan 1 1970 in_temp_offset -rw-rw-rw- 1 root root 4096 Jan 1 1970 in_temp_raw -rw-rw-rw- 1 root root 4096 Jan 1 1970 in_temp_scale -rw-rw-rw- 1 root root 4096 Jan 1 1970 in_voltage1_raw -rw-rw-rw- 1 root root 4096 Jan 1 1970 in_voltage2_raw -rw-rw-rw- 1 root root 4096 Jan 1 1970 in_voltage3_raw -rw-rw-rw- 1 root root 4096 Jan 1 1970 in_voltage_scale -rw-rw-rw- 1 root root 4096 Jan 1 1970 in_voltage_scale_available -rw-rw-rw- 1 root root 4096 Jan 1 1970 name lrwxrwxrwx 1 root root 0 Jan 1 1970 of_node -> ../../../../../../../firmware/devicetree/base/amba/i2c@e0004000/ad5593r@10 -rw-rw-rw- 1 root root 4096 Jan 1 1970 out_voltage0_raw -rw-rw-rw- 1 root root 4096 Jan 1 1970 out_voltage2_raw -rw-rw-rw- 1 root root 4096 Jan 1 1970 out_voltage3_raw -rw-rw-rw- 1 root root 4096 Jan 1 1970 out_voltage_scale -rw-rw-rw- 1 root root 4096 Jan 1 1970 out_voltage_scale_available drwxrwxrwx 2 root root 0 Jan 1 1970 power lrwxrwxrwx 1 root root 0 Jan 1 1970 subsystem -> ../../../../../../../bus/iio -rw-rw-rw- 1 root root 4096 Jan 1 1970 uevent root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2#
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2# grep "" * dev:252:2 in_temp_offset:-753 in_temp_raw:810 in_temp_scale:376.789750000 in_voltage1_raw:0 in_voltage2_raw:0 in_voltage3_raw:0 in_voltage_scale:0.610351562 in_voltage_scale_available:0.610351562 1.220703124 name:ad5592r out_voltage0_raw:0 out_voltage2_raw:0 out_voltage3_raw:0 out_voltage_scale:0.610351562 out_voltage_scale_available:0.610351562 1.220703124 uevent:MINOR=2 uevent:DEVNAME=iio:device2 uevent:DEVTYPE=iio_device uevent:OF_NAME=ad5593r uevent:OF_FULLNAME=/amba/i2c@e0004000/ad5593r@10 uevent:OF_COMPATIBLE_0=adi,ad5593r uevent:OF_COMPATIBLE_N=1
Show device name
This specifies any shell prompt running on the target
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2# cat name ad5593r
Scales
The output range of the DAC is 0 V to VREF or 0 V to 2 × VREF. out_voltage_scale is used to select the high or low range. Without external reference the driver selects the internal 2500mV VREF reference. So the scale computes as 2500mV/2^12 = 0.610351562 or 5000mV/2^12 = 1.220703124.
The input range of the ADC is 0 V to VREF or 0 V to 2 × VREF. in_voltage_scale is used to select the high or low range. Without external reference the driver selects the internal 2500mV VREF reference. So the scale computes as 2500mV/2^12 = 0.610351562 or 5000mV/2^12 = 1.220703124.
Show current scale
Description:
scale to be applied to out_voltageY_raw/in_voltageY_raw in order to obtain the measured voltage in millivolts.
This specifies any shell prompt running on the target
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2# cat out_voltage_scale 0.610351562
Show available scales
Description:
scale to be applied to out_voltageY_raw/in_voltageY_raw in order to obtain the measured voltage in millivolts.
This specifies any shell prompt running on the target
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2# cat in_voltage_scale_available 0.610351562 1.220703124
Change scales
Description:
scale to be applied to out_voltageY_raw/in_voltageY_raw in order to obtain the measured voltage in millivolts.
This specifies any shell prompt running on the target
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2# echo 1.220703124 > in_voltage_scale root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2# cat in_voltage_scale 1.220703124
Get channel Y input voltage
Description: Raw unscaled voltage measurement on channel Y
This specifies any shell prompt running on the target
This specifies any shell prompt running on the target
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2# cat in_voltage3_raw 1491
U = in_voltage3_raw * in_voltage_scale = 1491 * 0.610351562 = 910 mV
Set channel Y output voltage
Description:
Raw (unscaled, no bias etc.) output voltage for channel Y.
This specifies any shell prompt running on the target
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device2# echo 1638 > out_voltage0_raw
U = out_voltage0_raw * out_voltage_scale = 1638 * 0.610351562 = 999.76 mV
Example obtaining the temperature in °C
T = ( in_temp_raw + in_temp_offset ) * in_temp_scale
T = ( 810 - 753 ) * 376.78975 = 21477 mdeg C = 21.5 °C
For more information see also here: IIO Kernel Documentation
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/ad5592r.txt · Last modified: 19 Jan 2018 10:13 by Alexandru Ardelean