Capturing logic signals

In this chapter, we’re going to focus on how to simply capture some logic signals using an Ikalogic logic analyzer. Please note that for the sake of clarity, we’re not going to get into advanced features like configuring industrial inputs (like the ones that come with the SP209i or setting up complex triggers). Below we’re going to present a recommended approach when apprehending a new measurement. You may very well have you’re own (even better) techniques, so feel free to follow different approaches if you feel confident enough.

Step 1: setup the workspace

Connect your logic analyzer to your computer, and ensure it’s correctly installed. Start by creating a new workspace (simply hit CTRL+N, or click “create new workspace” button):

create new workspace

Select the right device from the list and create the workspace. If the device is correctly recognized by your computer, you should see the status indicator showing the device as “online” as shown in the image below:

SQ25 logic analyzer online

Step 2: Electrical connections

If your logic analyzer’s probes are not connected to the board under test, go ahead and connect it.

  • Before making any connection, ensure the voltage levels are within the operating range of the logic analyzer device.
  • Also ensure that the device under test is not connected to the mains and that there are no risks of ground loops, as this may be destructive for your board, your logic analyzer or in a worst-case scenario, your host computer to which your logic analyzer is connected.
  • Don’t forget to connect the ground of the logic analyzer to the ground of the board / device. A good - noise free - ground connection can make the difference between glitch-free captured signals and noisy captures.
  • Ensure your board/device is turned on.

Step 3: First capture

Now, we recommend capturing a first set of logic signals to get a general overview of the logic levels on the different channels and ensure all signals look as expected. The image below shows an example capture:

example logic signals

Please note that this totally depends on your board and the signals you’re observing and more importantly, the logic analyzer device configuration (threshold levels and sampling rate). In your case, you may see only flat signals, which may be normal and expected.

Step 4: Further configuration

If you don’t see expected signals, you may need to configure the logic levels (logic thresholds) and, if the logic analyzer device allows it, the sampling rate. You may change those parameters from the “Device” tab in ScanaStudio.

In some cases, you may need to setup a trigger to capture intermittent signals that occur only once in a while. We’re not going to explain what is a trigger, but very shortly, a trigger will let your logic analyzer device wait for a particular event before starting a capture. This configuration can be made in the “Trigger” tab, just under the device tab:

Trigger configuration

A very easy trigger configuration that lets your logic analyzer wait for any activity on the logic channels, is to wait for any change on any channel:

trigger on logic channel

Note: Both device configuration and trigger configuration will are handled in detail in other chapters.

Now that you know how to capture signals, it’s time to learn how to use the full potential of ScanaStudio and your logic analyzer and decode (interpret) captured signals!