RoadTest: Digilent Digital Discovery with High Speed Adapter
Author: vplacint
Creation date:
Evaluation Type: Test Equipment
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?: null
What were the biggest problems encountered?: null
Detailed Review:
Introduction
I want to thank to organizers, Digilent and element14, for choosing me to receive this device for tests. I have to tell you, it helped me a lot in terms of debugging my digital circuits, inside an FPGA.
I received the package completely, well packed and unharmed, as you can see in the following photos:
I am very impressed of this tool as its price/performance ratio seems to fit very well with student applications and also for professionals. I took the liberty to see how was designed, so I had a look at its PCB (as an embedded hardware engineer I couldn’t resist not to).
As you see, or maybe already know, they have done a good job, I like the way how they organized its layout.
For testing I performed the following tests:
-UART protocol;
-I2C protocol;
-SPI protocol;
-Parallel protocol & High Speed Recording;
-PWM measurements.
Graphical User Interface (GUI)
The Waveforms GUI (downloaded from here) is a good and well organized tool. You can save your worksheet, for later analysis, as well as control the entire device easily. Although I saw it crashing a few times on my system (Windows 10 OS with 64-bit), but I think these problems are most likely due my OS.
Testing
UART protocol
Using an Arduino Due dev board, I have made a firmware which allows me to make an USB-UART bridge between PC and Digital Discovery. It has the following configuration: 8 bits, no parity, 1 stop bit and 9600 baud rate. First tests were to see if the data are transmitted well to/from PC, while you can go deeper with the analyses and try to see the actual bits.
If you are debugging a system where you don’t know the baud rate you can determine it by measuring the pulse length of an actual bit and take its reciprocal value to determine the baud rate. Be sure you are sampling data at higher rates, to have accurate measurements.
I2C protocol
Using the same Arduino due board, I have made a firmware which sends something on I2C as a master. Using the logic functions, the I2C bus can be very well analyzed.
Moreover, since I am not very good with programming I manage to find an HMC5883L sensor, and using and I2C example from Waveforms library I manage to read its values. This function it can be very useful sometimes.
SPI protocol
The SPI protocol was inspected using an FPGA board which drives a 12-bit ADC, MAX1285. Its signals were cloned (buffered to other pins) inside the FPGA and connected to Digital Discovery device. Following photos shows the setup and the signals.
Parallel protocol & High Speed Recording
A 13-bit parallel bus was generated using FPGA with its values incremented at 100 MHz. I didn’t manage to measure with the high speed cables due some connectors incompatibilities with the FPGA board, hence the results are shown below:
PWM measurements
Six 12-bit PWM signals, 3 complementary phases, were generated using FPGA, and with the help of this tool I was able to see the accuracy of my logic along with its control response. I was able to measure the frequency as well as the duty cycle. See the following photos below:
Conclusions
This device, fits well in my applications, especially digital circuits and communication protocols inside the FPGAs/microcontrollers. As a main conclusion I am satisfied by its features, hence no major problems occurred. Also, the power supplies are stable, to bad that cannot be set independent from the I/Os.
I am looking forward to buy its analog version, Analog Discovery 2.
I hope my work will satisfy your needs/further questions, hence if you have something to ask me, just drop me a line here.
Many thanks again to organizers!
Best Regards,
Vlad-Mihai PLACINTA
