This version (20 Nov 2020 09:33) was approved by Alexandru Ardelean.The Previously approved version (20 Nov 2020 09:30) is available.
Table of Contents
nanoDAC+ IIO DAC Linux Driver
Supported Devices
Reference Circuits
Evaluation Boards
Description
This is a Linux industrial I/O (IIO) subsystem driver, targeting multi-channel serial interface DACs. 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 IIO for more information.
Source Code
Status
Files
Devicetree
Required devicetree properties for spi devices:
- compatible: Needs to be the name of the device. E.g. “ad5676”
- reg: The chipselect number used for the device
- spi-max-frequency: Maximum SPI clock frequency.
- spi-cpol: Needs to be set for the correct SPI mode
- vcc-supply: Phandle to the fixed regulator
- interrupts: the interrupt used for buffer sampling
- pwms: pwm pin used as the interrupt source
adc_vref: fixedregulator@0 {
compatible = "regulator-fixed";
regulator-name = "fixed-supply";
regulator-min-microvolt = <2500000>;
regulator-max-microvolt = <2500000>;
regulator-boot-on;
};
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
ad5676@0 {
compatible = "ad5676";
reg = <0>;
spi-max-frequency = <1000000>;
spi-cpha;
vcc-supply = <&adc_vref>;
interrupts = <25 IRQ_TYPE_EDGE_RISING>;
interrupt-parent = <&gpio>;
pwms = <&pwm 0 100>;
pwm-names = "pwm-trigger";
};
Required devicetree properties for i2c devices:
- compatible: Needs to be the name of the device. E.g. “AD5696”
- reg: The chipselect number used for the device
- vcc-supply: Phandle to the fixed regulator
- interrupts: the interrupt used for buffer sampling
- pwms: pwm pin used as the interrupt source
adc_vref: fixedregulator@0 {
compatible = "regulator-fixed";
regulator-name = "fixed-supply";
regulator-min-microvolt = <2500000>;
regulator-max-microvolt = <2500000>;
regulator-boot-on;
};
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
ad5696@e {
compatible = "ad5696";
reg = <0xe>;
vcc-supply = <&adc_vref>;
interrupts = <25 IRQ_TYPE_EDGE_RISING>;
interrupt-parent = <&gpio>;
pwms = <&pwm 0 100>;
pwm-names = "pwm-trigger";
};
Driver testing
This specifies any shell prompt running on the target
root:/> cd /sys/bus/iio/devices/ root:/sys/bus/iio/devices> ls iio:device0 root:/sys/bus/iio/devices> cd iio\:device0 root:/sys/bus/iio/devices/iio:device0> ls -l drwxr-xr-x 2 root root 0 Jul 31 15:17 buffer -r--r--r-- 1 root root 4096 Jul 31 15:17 dev -r--r--r-- 1 root root 4096 Jul 31 15:17 name lrwxrwxrwx 1 root root 0 Jul 31 15:17 of_node -> ../../../../../../../../firmware/devicetree/base/soc/spi@7e204000/ad5679r@0 -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage0_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage0_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage0_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage10_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage10_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage10_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage11_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage11_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage11_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage12_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage12_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage12_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage13_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage13_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage13_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage14_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage14_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage14_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage15_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage15_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage15_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage1_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage1_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage1_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage2_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage2_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage2_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage3_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage3_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage3_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage4_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage4_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage4_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage5_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage5_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage5_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage6_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage6_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage6_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage7_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage7_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage7_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage8_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage8_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage8_raw -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage9_powerdown -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage9_powerdown_mode -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage9_raw -r--r--r-- 1 root root 4096 Jul 31 15:17 out_voltage_powerdown_mode_available -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage_sampling_frequency -rw-r--r-- 1 root root 4096 Jul 31 15:17 out_voltage_scale drwxr-xr-x 2 root root 0 Jul 31 15:17 power drwxr-xr-x 2 root root 0 Jul 31 15:17 scan_elements lrwxrwxrwx 1 root root 0 Jul 31 15:17 subsystem -> ../../../../../../../../bus/iio drwxr-xr-x 2 root root 0 Jul 31 15:17 trigger -rw-r--r-- 1 root root 4096 Jul 31 15:17 uevent
Show device name
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> cat name ad5696
Show scale
Description:
scale to be applied to in_voltage0_raw in order to obtain the measured voltage in millivolts.
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> cat out_voltage_scale 0.038146972
Set channel Y output voltage
Description:
/sys/bus/iio/devices/deviceX/out_voltageY_raw
Raw (unscaled, no bias etc.) output voltage for channel Y.
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> echo 10000 > out_voltage0_raw
U = out_voltage0_raw * out_voltage_scale = 10000 * 0.038140 = 381.40 mV
List available power down modes
/sys/bus/iio/devices/deviceX/out_powerdown_mode_available
Description:
Lists all available output power down modes.
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> cat out_voltage_powerdown_mode_available 1kohm_to_gnd 100kohm_to_gnd three_state
Set channel Y power down mode
/sys/bus/iio/devices/deviceX/out_voltageY_powerdown_mode
Description:
Specifies the output power down mode.
DAC output stage is disconnected from the amplifier and
| 1kohm_to_gnd | connected to ground via an 1kOhm resistor |
| 100kohm_to_gnd | connected to ground via an 100kOhm resistor |
| three_state | left floating |
For a list of available output power down options read out_voltageX_powerdown_mode_available.
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> echo three_state > out_voltage0_powerdown_mode root:/sys/bus/iio/devices/iio:device0> cat out_voltage0_powerdown_mode three_state
Enable power down mode on output Y
/sys/bus/iio/devices/deviceX/out_voltageY_powerdown
Description:
Writing 1 causes output Y to enter the power down mode specified
by the corresponding out_voltageY_powerdown_mode. Clearing returns to
normal operation. Y may be suppressed if all outputs are
controlled together.
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> echo 1 > out_voltage0_powerdown root:/sys/bus/iio/devices/iio:device0> cat out_voltage0_powerdown 1 root:/sys/bus/iio/devices/iio:device0> echo 0 > out_voltage0_powerdown root:/sys/bus/iio/devices/iio:device0> cat out_voltage0_powerdown 0
Buffer Support
Description:
The nanoDAC family of devices has buffer support for changing the output of the DAC channels. To achieve this a PWM signal is used as the device trigger to output data. Using a sampling frequency attribute the period of the PWM signal can be changed. The sampling frequency is in Hz.
In order to use this functionality the interrupt pin must be tied to the PWM generation pin
This specifies any shell prompt running on the target
root@analog:/sys/bus/iio/devices/iio:device0 $ cat out_voltage_sampling_frequency 1000 root@analog:/sys/bus/iio/devices/iio:device0# echo 2000 > out_voltage_sampling_frequency root@analog:/sys/bus/iio/devices/iio:device0# cat out_voltage_sampling_frequency 2000
Enable buffered channels
Description:
The user has to enable on what channels to output the buffer samples. The samples are interleaved in the following in the order of the enabled channels.
Example:
sample_ch0|sample_ch1|sample_ch2
If only channel 1 is enabled the buffer samples will have the following configuration:
sample_ch1|sample_ch1|sample_ch1
This specifies any shell prompt running on the target
root@analog:/sys/bus/iio/devices/iio:device0# cd scan_elements/ root@analog:/sys/bus/iio/devices/iio:device0/scan_elements# ls out_voltage0_en out_voltage10_type out_voltage12_index out_voltage14_en out_voltage15_type out_voltage2_index out_voltage4_en out_voltage5_type out_voltage7_index out_voltage9_en out_voltage0_index out_voltage11_en out_voltage12_type out_voltage14_index out_voltage1_en out_voltage2_type out_voltage4_index out_voltage6_en out_voltage7_type out_voltage9_index out_voltage0_type out_voltage11_index out_voltage13_en out_voltage14_type out_voltage1_index out_voltage3_en out_voltage4_type out_voltage6_index out_voltage8_en out_voltage9_type out_voltage10_en out_voltage11_type out_voltage13_index out_voltage15_en out_voltage1_type out_voltage3_index out_voltage5_en out_voltage6_type out_voltage8_index out_voltage10_index out_voltage12_en out_voltage13_type out_voltage15_index out_voltage2_en out_voltage3_type out_voltage5_index out_voltage7_en out_voltage8_type root@analog:/sys/bus/iio/devices/iio:device0/scan_elements# echo 1 > out_voltage0_en root@analog:/sys/bus/iio/devices/iio:device0/scan_elements# cd ../buffer/ root@analog:/sys/bus/iio/devices/iio:device0/buffer# ls data_available enable length watermark root@analog:/sys/bus/iio/devices/iio:device0/buffer# echo 1 > enable
Sending a buffer sample example:
This specifies any shell prompt running on the target
root@analog:/sys/bus/iio/devices/iio:device0/buffer# echo -n -e '\x22\x33' > /dev/iio\:device0
More Information
- IIO mailing list: linux [dash] iio [at] vger [dot] kernel [dot] org
resources/tools-software/linux-drivers/iio-dac/ad5676.txt · Last modified: 20 Nov 2020 09:32 by Alexandru Ardelean