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This version (15 Mar 2019 08:14) was approved by aardelean.The Previously approved version (27 Apr 2016 17:14) is available.Diff

AD9834 IIO Direct Digital Synthesis Linux Driver

Supported Devices

Reference Circuits

Evaluation Boards

Description

This is a Linux industrial I/O (IIO) subsystem driver, targeting serial interface DDS controllers. 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

Source Mainlined?
git Yes

Files

Example device-tree

In the example below, it's assumed that spi0 is the SPI controller to which the AD983X is attached to. Typically, these are defined in the board device-tree where the AD983X is attached to.

	&spi0 {
		#address-cells = <1>;
		#size-cells = <0>;
		status = "okay";
 
		ad9833@0{
			#clock-cells = <0>;
			compatible = "adi,ad9833";
			reg = <0>;
			spi-max-frequency = <1000000>;
			spi-cpol;
			clocks = <&osc>;
			vcc-supply = <&vcc>;
		};
	};

This example also references a regulator (vcc-supply) and a clock (osc). These can be left out, in which case it's assumed they are somehow hard-wired on the board to a proper voltage supply and clock source.

The compabtible string can be any of the following:

  • adi,ad9833
  • adi,ad9834
  • adi,ad9837
  • adi,ad9838

Note that, the *adi,* prefix can be omitted and this still works. It is preferred to be added to avoid any potential collisions with other drivers from other vendors.

However, the voltage supply & clock can be defined via device-tree as well. See example below:

	/ {
		vcc: fixedregulator@0 {
			compatible = "regulator-fixed";
			regulator-name = "fixed-supply";
			regulator-min-microvolt = <2500000>;
			regulator-max-microvolt = <2500000>;
			regulator-boot-on;
		};
 
		osc: oscillator {
			#clock-cells = <0>;
			compatible = "fixed-clock";
			clock-frequency = <25000000>;
		};
	};

This assumes that the board has the chips & drivers to generate voltages like this & clock frequencies.

Adding Linux driver support

Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)

The AD9834 Driver depends on CONFIG_SPI

Linux Kernel Configuration
	Device Drivers  --->
		[*] Staging drivers  --->
			<*>     Industrial I/O support --->
			    --- Industrial I/O support
			    -*-   Enable ring buffer support within IIO
			    -*-     Industrial I/O lock free software ring
			    -*-   Enable triggered sampling support

			          *** Direct Digital Synthesis ***
			    [--snip--]

			    <*>   Analog Devices ad9833/4/ driver

			    [--snip--]

Hardware configuration

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.

02 Mar 2011 15:16

This specifies any shell prompt running on the target

root:/> cd /sys/bus/iio/devices/
root:/sys/bus/iio/devices> ls
device0
root:/sys/bus/iio/devices> cd device0

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> ls -l
--w-------    1 root     root          4096 Jan  3 14:06 dds0_freq0
--w-------    1 root     root          4096 Jan  3 14:06 dds0_freq1
-r--r--r--    1 root     root          4096 Jan  3 14:06 dds0_freq_scale
--w-------    1 root     root          4096 Jan  3 14:06 dds0_freqsymbol
--w-------    1 root     root          4096 Jan  3 14:06 dds0_out0_wavetype
-r--r--r--    1 root     root          4096 Jan  3 14:06 dds0_out0_wavetype_available
--w-------    1 root     root          4096 Jan  3 14:06 dds0_out1_enable
--w-------    1 root     root          4096 Jan  3 14:06 dds0_out1_wavetype
-r--r--r--    1 root     root          4096 Jan  3 14:06 dds0_out1_wavetype_available
--w-------    1 root     root          4096 Jan  3 14:06 dds0_out_enable
--w-------    1 root     root          4096 Jan  3 14:06 dds0_phase0
--w-------    1 root     root          4096 Jan  3 14:06 dds0_phase1
-r--r--r--    1 root     root          4096 Jan  3 14:06 dds0_phase_scale
--w-------    1 root     root          4096 Jan  3 14:06 dds0_phasesymbol
--w-------    1 root     root          4096 Jan  3 14:06 dds0_pincontrol_en
-r--r--r--    1 root     root          4096 Jan  3 14:06 name
drwxr-xr-x    2 root     root             0 Jan  3 14:06 power
lrwxrwxrwx    1 root     root             0 Jan  3 14:06 subsystem -> ../../../../../bus/iio
-rw-r--r--    1 root     root          4096 Jan  3 14:06 uevent

Show device name

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat name
ad9834

Show frequency scale

/sys/bus/iio/devices/…/ddsX_freqY_scale

Scale to be applied to ddsX_freqY in order to obtain the desired value in Hz. If shared across all frequency registers Y is not present. It is also possible X is not present if shared across all channels.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat dds0_freq_scale
1

Set frequency symbol 0/1

/sys/bus/iio/devices/…/ddsX_freqY

Stores frequency into tuning word Y. There will be more than one ddsX_freqY file, which allows for pin controlled FSK Frequency Shift Keying (ddsX_pincontrol_freq_en is active) or the user can control the desired active tuning word by writing Y to the ddsX_freqsymbol file.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 1000000 > dds0_freq0
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 500000 > dds0_freq0

freq0 = ddsX_freq0 * dds0_freq_scale = 1000000 * 1 = 1 MHz
freq1 = ddsX_freq1 * dds0_freq_scale = 500000 * 1 = 500 kHz

Show phase scale

/sys/bus/iio/devices/…/ddsX_phaseY_scale

Scale to be applied to ddsX_phaseY in order to obtain the desired value in rad. If shared across all phase registers Y is not present. It is also possible X is not present if shared across all channels.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat dds0_phase_scale
0.0015339808

Set phase symbol 0/1

/sys/bus/iio/devices/…/ddsX_phaseY

Stores phase into Y. There will be more than one ddsX_phaseY file, which allows for pin controlled PSK Phase Shift Keying (ddsX_pincontrol_phase_en is active) or the user can control the desired phase Y which is added to the phase accumulator output by writing Y to the en_phase file.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 512 > dds0_phase0
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 2048 > dds0_phase0

phase0 = dds0_phase0 * ddsX_phaseY_scale = 512 * 0.0015339808 = 0.7853981696 rad
phase1 = dds0_phase1 * ddsX_phaseY_scale = 2048 * 0.0015339808 = PI = 3.1415926 rad

List available wavetypes

/sys/bus/iio/devices/…/ddsX_outY_wavetype_available

Lists all available output waveform options.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> cat dds0_out0_wavetype_available
sine triangle

Set wavetype

/sys/bus/iio/devices/…/ddsX_outY_wavetype

Specifies the output waveform. (sine, triangle, ramp, square, …) For a list of available output waveform options read available_output_modes.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo sine > dds0_out0_wavetype

Disable FSK/PSK pincontrol

/sys/bus/iio/devices/…/ddsX_pincontrol_en

ddsX_pincontrol_en: Both, the active frequency and phase is controlled by the respective phase and frequency control inputs. In case the device in question allows to independent controls, then there are dedicated files (ddsX_pincontrol_freq_en, ddsX_pincontrol_phase_en).

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 0 > dds0_pincontrol_en

Enable output 0

/sys/bus/iio/devices/…/ddsX_out_enable
/sys/bus/iio/devices/…/ddsX_outY_enable

ddsX_outY_enable controls signal generation on output Y of channel X. Y may be suppressed if all channels are controlled together.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 1 > dds0_out_enable

Switch between frequency symbol 0/1

/sys/bus/iio/devices/…/ddsX_freqsymbol

Specifies the active output frequency tuning word. The value corresponds to the Y in ddsX_freqY. To exit this mode the user can write ddsX_pincontrol_freq_en or ddsX_out_enable file.

This specifies any shell prompt running on the target

root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 1 > dds0_freqsymbol
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0> echo 0 > dds0_freqsymbol
root:/sys/devices/platform/bfin-spi.0/spi0.3/device0>

More Information

resources/tools-software/linux-drivers/iio-dds/ad9834.txt · Last modified: 15 Mar 2019 08:14 by aardelean