How to speed up serial communication on Windows

Posted on By Charity Carter

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.
  • Step 1: Device Manager
  • Step 2: USB Port Properties
  • Step 3: 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.

  • Latency Timer set to 16ms
  • Latency Timer set to 8ms
  • Latency Timer set to 1ms

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!

Using the CAB8 and CAB12 without an interposer

Posted on By Josh

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

Which driver is right for you?

Posted on By Josh

Choosing a driver for your photonic device can be a difficult task. Though we hope that our drivers are the best fit, there are several parameters to keep in mind.

  • How much current does each input of my device require?
  • How much voltage is required to achieve this current?
  • What is the resistance of my on-chip heaters?
  • What precision do I need?
  • Does my device care about the direction of current flow?
  • How many inputs does my device have that need to be driven?