Testing waveform generation functions

03 December 2012

The openDAQ’s standard firmware has a powerful feature that allows the possibility to generate predefined waveforms through the DAC output using Stream Mode. The points of one cycle in a periodic waveform are charged into the memory of one of the DataChannel structures and then, when the experiment is carried out, the periodic signal will be emitted on DAC output.

The EasyDAQ demo can be configured to generate typical periodic signals like sine, square, triangle or saw tooth waveforms. It also allows loading the output data points from an external text archive (CSV), or loading the waveform into Burst Mode, which makes possible to generate much faster signals.

In this article we are just trying to test the basic functionalities of the device regarding waveform generation, and so we are going to use the EasyDAQ demo interface. You can download EasyDAQ from the git repository for openDAQ.

After launching the program and connecting to the device, the first thing that we make is to activate one of the channels (Experiment 1) to read ADC values from A8 each 20ms. We use that input as single-ended (Ch- connected to ground) and we are using +-2V input range. Previously, we have used a jumper wire to connect DAC output to A8 input within the same device.

With that configuration, we perform different tests:

  • Square wave: We configure a square wave output, with -100mV of offset and 200mV of amplitude. Total period is set to 1s and “time on” is configured to be 400ms. You can see the result in the following figure:

  • Sine wave: Then, we try the device with a sine wave output. We keep the period to be 1s, and we configure offset=200mV and amplitude as 300mV.

  • Saw tooth wave: Last, we configure a sawtooth periodic dac output. Now the period will be 900ms, offset 300mV and amplitude 900mV.

As you can see, the management of this utility is extremely simple.

In next articles we will see how to configure more advanced settings using this feature.