AD9834
AD9834 IIO Direct Digital Synthesis.
Supported Devices
Reference Circuits
Evaluation Boards
Description
This is a Linux industrial I/O (Linux Industrial I/O Subsystem) 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 Linux Industrial I/O Subsystem for more information.
Source Code
Status
Files
Function |
File |
|---|---|
driver |
|
include |
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)
Note
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.
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
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.
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.
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.
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.
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.
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.
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).
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.
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.
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>