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AD7303 IIO DAC Linux驱动程序
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Table of Contents
AD7303 IIO DAC Linux Driver
Supported Devices
Evaluation Boards
Description
This is a Linux industrial I/O (IIO) subsystem driver, targeting single-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
| Function | File |
|---|---|
| driver | drivers/iio/dac/ad7303.c |
Example platform device initialization
Devicetree
Required devicetree properties:
- compatible: Needs to be “adi,” followed by the name of the device. E.g. “adi,ad5541a”
- reg: The chipselect number used for the device
- spi-max-frequency: Maximum SPI clock frequency
- Vdd-supply: VDD voltage supply regulator
Optional devicetree properties:
- REF-supply: external reference voltage supply regulator. This should only be set if there is an external reference voltage connected to the REF pin. If not set, Vdd/2 is used as the reference voltage.
dac_vdd: fixedregulator@0 {
compatible = "regulator-fixed";
regulator-name = "fixed-supply";
regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
regulator-boot-on;
};
axi_spi_0: spi@42000000 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "xlnx,axi-spi-1.02.a", "xlnx,xps-spi-2.00.a";
...
ad7303@0 {
compatible = "adi,ad7303";
reg = <0>;
spi-max-frequency = <1000000>;
Vdd-supply = <&dac_vdd>;
};
};
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.
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 5 05:10 buffer -r--r--r-- 1 root root 4096 Jul 5 05:10 dev -r--r--r-- 1 root root 4096 Jul 5 05:10 name -rw-r--r-- 1 root root 4096 Jul 5 05:10 out_voltage0_powerdown -rw-r--r-- 1 root root 4096 Jul 5 05:10 out_voltage0_raw -rw-r--r-- 1 root root 4096 Jul 5 05:10 out_voltage1_powerdown -rw-r--r-- 1 root root 4096 Jul 5 05:10 out_voltage1_raw -rw-r--r-- 1 root root 4096 Jul 5 05:10 out_voltage_scale drwxr-xr-x 2 root root 0 Jul 5 05:10 power drwxr-xr-x 2 root root 0 Jul 5 05:10 scan_elements lrwxrwxrwx 1 root root 0 Jan 1 1970 subsystem -> ../../../../../../../bus/iio drwxr-xr-x 2 root root 0 Jul 5 05:10 trigger -rw-r--r-- 1 root root 4096 Jan 1 1970 uevent
Show device name
This specifies any shell prompt running on the target
root:/sys/bus/iio/devices/iio:device0> cat name ad7303
Show scale
Description:
scale to be applied to out_voltage0_raw and out_voltage1_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 12.890625
Set channel Y output voltage
Description:
/sys/bus/iio/devices/iio: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 100 > out_voltage0_raw
U = out_voltage0_raw * out_voltage_scale = 100 * 12.890625 mV = 1289.0625 mV
Enable power down mode on output Y
/sys/bus/iio/devices/iio:deviceX/out_voltageY_powerdown
Description:
Writing 1 causes output Y to enter the power down mode. Clearing returns to normal operation.
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
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