Diddy -- for Menlo DDS-120

Diddy is an unofficial Python library for communication with the DDS-120 of Menlo Systems. "Unofficial" here meaning that the work is neither sanctioned nor officially supported by Menlo.

Installation

Currently only installation from sources/GitLab is available:

$ git clone https://gitlab.com:codedump2/diddy
$ cd diddy
$ pip install .

Alternatively, if you have a Python >= 3.11, you can install Diddy as an in-place "editable" package, allowing you to modify code and have it available as if it were regularly installed, by changing the last line to this:

$ pip install . -e

Setup

The DDS-120 communicates with the PC via a serial interface. Typically that's something like /dev/ttyUSB0 or similar. Mostly, as a regular user you don't have the required permissions to access the device. A quick and dirty way of doing that is issuing a chmod 0666 as root. For most distrbutions, assinging your user to the dialout group will mostly grant you privileges to the tty class of devices.

A persistent way of doing this is by setting up proper udev rules. One way to do this is to create a file /etc/udev/99-menlodds.rules with the following contents:

KERNEL=="ttyUSB*",ATTRS{idVendor}=="0403",ATTRS{idProduct}=="6001",ATTRS{product}=="DDS", MODE="0666",SYMLINK+="menlodds%n"

Then issue the udev commands for reloading:

$ sudo udevadm control --reload
$ sudo udevadm trigger

This should trigger re-initialization of all USB devices, inlcuding the USB-to-serial converter incorporated in the Menlo DDS-120. If successful, it will create a device /dev/menlodds0 that everybody can use.

Note that you might want to change permissions (away for 0666 giving everyone logged into the system access), or may want to change ownership. Refer to udev documentation for details.

Usage

There's not much to Diddy; essentially, all the magic happens in a Python object DdsIo (here's assuming that the DDS-120 is attached as /dev/ttyUSB0 -- change accordingly e.g. if the device is named /dev/menlodds0):

dds = DdsIo("/dev/ttyUSB0")
print (dds.settings)

In the example above a property settings of DdsIo was used. It displays a JSON formatted summary of the device settings.

Other properties are as follows. Most of these can be either read (to report current values) or set (to change corresponding values within the DDS-120). Please refer to the DDS-120 documentation, or ask the manufacturer for details, as to what these parameters actually do. For each of these there's a 1:1 correspondence in the device's official documentation:

• remoteControl: set to True or False, depending on whether a PC is currently controlling the DDS-120

• amplitude: the current signal amplitude

• frequencyHz: the current frequency, in Hz

• phaseDeg: singnal phase, in degrees

• outputChannel: which output channel is used

• configuration: this is a cryptic, but otherwise human-readable string which sets up specific work parameters of DDS-120. As of January 2023, the set function is broken (inside the DDS-120 itself), only reading works. But Diddy in principle supports setting, too.

• firmwareVersion: read-only property that returns the self-reported DDS-120 firmare information

• serialNumber: read-only property that returns self-reported device identity information.

• frequencyOffset: the DDS-120 documentation refers to a command ("GO") that is supposed to report to return a frequency offset; this is implemented here, but apparently is rejected by the device.

Enjoy. As always, if you break it, it you get to keep both pieces :-)

F.