Selecting an Inexpensive LOGIC ANALYZER
Figure 1. DigiView DV1-100 logic analyzer equipment.
Figure 2. Inside the DV1-100.
DigiView DV1-100
I won’t repeat the device specifications here. You can find the details of the device on the TechTools website.
I’ll just give a brief overview of my use of the equipment. I received the hardware within 24 hours of ordering it and
it came nicely packed with all the pieces, CDROM, and a printed user’s manual (see Figure 1). The product comes
with micro-clip leads, but I have been using the raw connectors, which fit 0.025 inch square posts (stackable on 0.1
inch centers).
The DV1-100 has a screw panel on the back. I couldn’t resist looking inside. The device consists of the FTDI
FT245BM USB IC, a Samsung K7A403600A SRAM, and a Quicklogic QL3025 ASIC (Figure 2). You can download
the software from the Tech Tools website. It uses an InstallShield installation procedure and the download includes the
USB drivers. The printed manual appears to be identical to the online help, so, if you do download the software, you
pretty much have everything except for the hardware. The software includes some test data, so you can examine the
capabilities of the display.
The GUI
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The main window shows the recorded data. There are pushbuttons for File, Help, Configure, Run/Stop, and
Time, which is displayed in seconds, milliseconds, microseconds, and nanoseconds. The “File” menu allows the user
to open, save, print, and exit. The Open/Save option allows the user to save data and Email it to someone else. The
RUN button is disabled unless the hardware is detected. An example of a test sequence is shown in Figure 3.
In this display, I have zoomed out to show the change of the slower signals (three-phases at 100 Hz and three-phases at 60 Hz). I’m working out some noise issues with the hardware, so there is some signal switching where it
shouldn’t be. The software allows the user to zoom in and out on the data, center on the trigger, and set two snap
lines that provide a measure of time between the two snap lines. Data files that I recorded were approximately 700
kbytes and compressing with ZIP reduced the file size by about 50%. This resulted in a file size that was easy to Email.
This feature has been very useful for discussing results with the other team members that are working on the
project.
The Configure pushbutton brings up a configuration window (Figure 4) that allows signals and triggers to be
defined. A trigger can be assigned to any channel or combination of channels and can be level, edge triggered, or
both, so you can trigger on multiple events. The wire color code is the same as the color code for resistors. This
configure screen also allows auto save/restore and prefill to be enabled. The DigiView is always sampling and
storing data in a circular buffer. This uses half of the capacity. When a trigger event occurs, DigiView fills the other
half of the buffer or runs until the “Stop” pushbutton is pressed. Thus, the “trigger” event occurs at the midway point
in the data. Time before the trigger event is shown as negative. Depending on how fast the data is changing,
sometimes you have to press “Stop” because with compression, it can take several seconds to fill the remaining
buffer. I found the software easy to use and intuitive.
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JULY 2004
