Table of Contents
Introduction
Labrador's waveform generators are fully programmable and drive an 8-bit, 1MSPS DAC with a 512-byte buffer.
This means that it's possible to define any custom wave shape you like!
To do so, you'll need to create a .tlw file.
There are some sample files located under the waveforms directory beside the Labrador executable (on Windows, this would be C:\Program Files\EspoTek\EspoTek Labrador\waveforms).
.tlw Files
Opening a sample .tlw file in a text editor, you will find that each file consists of three lines.
The first line defines the number of samples in the waveform. This number can range from 1 to 512.
The second line defines the "binary downsampling" parameter. For most custom waveforms, you'll want to set this to 1. Setting it above 1 allows the Labrador software to reduce the sample count in order to extend the frequency. As this is an advanced topic, it's explained at the bottom.
The third line contains a list of each of the samples, separated by tabs. Each sample should be in the range 0 to 255, where 0 represents minimum voltage, and 255 represents maximum.
For example, here is Triangle.tlw:
128
4
0 4 8 12 16 20 24 28 32 36 40 45 49 53 57 61 65 69 73 77 81 85 89 93 97 101 105 109 113 117 121 125 130 134 138 142 146 150 154 158 162 166 170 174 178 182 186 190 194 198 202 206 210 215 219 223 227 231 235 239 243 247 251 255 255 251 247 243 239 235 231 227 223 219 215 210 206 202 198 194 190 186 182 178 174 170 166 162 158 154 150 146 142 138 134 130 125 121 117 113 109 105 101 97 93 89 85 81 77 73 69 65 61 57 53 49 45 40 36 32 28 24 20 16 12 8 4 0
_list.wfl
Once you have defined your custom waveform in a .tlw file, the last step is to add your waveform's name to _list.wfl.
This file is also located in the waveforms directory, alongside the sample .tlw files.
To add your custom waveform to _list.wfl, simply add a line to the file consisting of the name of your .tlw file.
Note that the order in which the waveforms are defined in _list.wfl is the order in which they will appear in the Labrador Software's UI.
A Note on Binary Downsampling
As the DAC is only capable of outputting 1MSPS, the maximum frequency that your waveform can be produced is limited by the sample count. For example, the maximum frequency a waveform with 500 samples can be generated at is 2kHz (2kHz * 500 samples = 1MSPS).
To get around this limitation, the in-built waveforms define use a "binary downsampling" parameter greater than 1. A binary downsampling parameter of 2 means that the software can discard every second sample in order to increase the frequency above the maximum (in our example above, it would allow the software to automatically scale the waveform to 250 samples in order to allow a maximum frequency of 4kHz. However, it would use the full 500 samples if the frequency was set to 2kHz or below).
Increasing this value to 3 would allow the software to discard more samples - in the case of our example, it would allow the software to extend the range to 8kHz by discarding all but 125 samples.
Long story short, increasing this value by 1 allows the software to halve the sample count and double the frequency.