How to speed up serial communication on Windows

Changing the latency timer on a Windows PC can reduce the delay between transmitting two commands. Here is a step-by-step guide on how to do this!

  1. Open the Device Manager > Port (COM & LPT) > USB Serial Port (COM7). Note that the COM port number will likely be different on your machine.
  2. Right-click USB Serial Port and select Properties then navigate through
    Properties > Port Settings > Advanced.
  3. Using the Advanced tab, we can adjust the Latency Timer.

The latency timer controls the time interval between two commands in serial communication. We can confirm this by observing the communications signal on an oscilloscope.

In the above, blue lines are commands sent from the PC and red lines are the Qontrol hardware response. We used two Q8b modules in this experiment, hence there are two commands and two responses.

And that’s it! We hope this short tutorial has helped you make the most of your Qontrol modules. If you have any questions, as always, please contact us and we would be happy to help!

Motion Qontrol is Here

We at Qontrol are thrilled to announce today the first (micro)steps in an exciting new direction for us: motion control.

When the pandemic struck, in early 2020, we asked ourselves what we could do to help the world carry on the important business of moving photonics and quantum photonics forward. What the pandemic threw into stark relief is that many photonics labs still rely critically on human power to operate positioners, fibre-couplers, rotation mounts, delay lines, and many other crucial optical elements. Typical optomechanical motion control systems are high cost and inflexible, and general purpose motion control hardware tends to be imprecise and half-baked. Motion control with the right combination of cost, power, and precision—for photonics—needs to be scaled up. At Qontrol, scaling things up intelligently is our bread and butter.

Today we are releasing a suite of products which will immediately enable photonic engineers and scientists to control multi-axis positioners for tasks such as fibre and V-groove array alignment, probe placement, and fibre-to-free-space alignment.


The core to our new offering is the M2 motor controller module. It offers independent control of two stepper motors, with enough precision and power needed for lab automation. It offers:

  • 256 microsteps per full step
  • 1.3 amps per motor winding
  • 6200 microsteps per second
  • scalable integration with other Qontrol modules


Our Python API fully supports the M2, and we will be issuing regular updates to the codebase as time goes on. You can contribute to the effort by sending pull requests to our GitHub.

The latest API is always available to be cloned from GitHub, or the latest stable release is available from the Python Package Index (PyPi).


Our first actuator, the ACTL2, can be put to use immediately, powered by the M2 motor controller, and mounted on a multi-axis stage flavour found in many labs across the world: the MAX300 and MAX600 series of stages from Thorlabs.

The ACTL2 offers:

  • 3.175 µm full-step resolution
  • 19.6 mm travel range
  • helical thumb wheel
  • single-end interlock

With a tactile helical thumb wheel, the direction of the actuator’s travel is visible, and the position can be manually adjusted. A single internal interlock switch allows homing and absolute positioning (especially after manual adjustment). When controlled by our M2 module, the ACTL2 can achieve a microstep resolution of 19 nanometres! See it in action:

The ACTL2 mounts to a male M22x0.75 thread via a rotating barrel mechanism with four locking screws. These can be easily tightened in the cramped spaces of a typical multi-axis stage setup using our ACTM25 ball-end thumb screw.


And we have created a new backplane, the BP3M, to connect six motors and conveniently match the six degrees of freedom of space. The BP3M hosts three M2 modules, and breaks these connections out to six CABM6 cables, compatible with the ACTL2. It provides the usual USB communications and power-entry connector of our other backplanes, but leaves out the CABCHN chain interface.

Get things moving!

Like what you see? Have ideas for what’s next? Get in touch with us at [email protected], or for sales enquiries, at [email protected]. Let’s get photonics moving again.

Using the CAB8 and CAB12 without an interposer

Though our interposers offer a wide variety of connectivity options, you may want to just plug the bulky CAB8 or CAB12 directly into your application. We use high-density D-sub connectors from the AMP-TE AMPLIMITE 0.50 Series, which can be purchased from any of the large online distributors (e.g. Farnell, Digikey, Mouser). Part numbers for right-angle and vertical connectors are listed in the table below.

Continue reading Using the CAB8 and CAB12 without an interposer

See you at BQIT 2019!

We’re happy to announce that we are a Bronze sponsor at this year’s Bristol Quantum Information Technologies Workshop BQIT, April 1-3. This is really exciting for us because it’s the first conference we have sponsored, and it’s with our favourite people, QETlabs, here in Bristol.

We’ll have a booth set up with some demos throughout the conference, and both of us (Liz and Josh) will be there, so come and say hi. Come check out our existing products, and an exciting new product to launch too! And don’t forget to pick up some swag-nets while you’re at it.

How to connect to your chip

This question comes up often. In this post, we outline some of the different approaches and discuss the interposers which we stock for various scenarios. If none of our existing interposers meet your needs, please contact us with your special product request.

We stock a variety of interposer PCBs. These take in the bulky 60 or 68-way cables from our line of docks and break them out into smaller connectors for wiring your devices. Most interposers present two or more identical output connectors. Some contain integrated patch panels, to allow manual re-wiring of the device. Others are directly wired, and rely on reconfiguration in software.

Continue reading How to connect to your chip