Cheap Xilinx Virtual Cable Alternative?

Projects / FPGA  Original post date: 02/07/2015

One of the biggest grief of using Windows 7 x64 is that I have to upgrade my programming tools. While I managed to find a cone Altera cable for $6, Xilinx clone was about $30. Even if I want to spend the cash, I would add yet another programming dongle to my collection. See picture of a subset of my collection so far.

Is there a different way of doing this? It turns out that Xilinx implemented a JTAG protocol that allow for remote programming access to embedded system over IP. If we can implement a user mode program that can communicate with the protocol and to toggle the appropriate JTAG signals, we've got ourselves a virtual cable that is fully supported by the ISE.

If you are using a linux machine, you can skip ahead and modify xvcd (Xilinx Virtual Cable Daemon) source code.

I ordered a ESP8266 earlier today while ordering parts for fixing my scope. I have been procrastinating of using it as a JTAG programmer.  Someone did all the hard work and made a ESP8266 JTAG programmer.  Sometimes it pays off.
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https://github.com/gtortone/esp-xvcd

ESP8266 Xilinx Virtual Cable
ESP8266 implementation of XVC (Xilinx Virtual Cable) protocol based on xvcd (https://github.com/tmbinc/xvcd)
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http://compgroups.net/comp.arch.embedded/esp8266-based-xilinx-virtual-cable-server/3029298

The first results seem to be promising, but unfortunately, I have found information about serious problems with XVC plugin in ISE14 (which still has to be used for older Xilinx FPGAs).
The problem is reported here:
http://forums.xilinx.com/t5/Design-Tools-Others/iMPACT-XVC-broken-with-multiple-devices/td-p/496232
And it is not clear if Xilinx is going to fix it :-(.
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Here is a little preview of what I am working on:

I made/planned for some changes:

• Level translation for the JTAG signal added.
• GPIO changes to HSPI pins.
• Firmware (long term goal).  This is my first with ESP8266.

1. Hotspot mode to Hotspot/AP
2. Recode inefficient Arduino digitalwrite() to bare metal GPIO access and purge the dependency from their framework. 
3. Not sure if HSPI can help to speed up some of the JTAG bit shifting.

What the layout would look like:

I didn't do a good job on the toner transfer this time.  There was a lot of shorts and a couple of broken traces that I have to patch.  Even the USB micro connector has a couple of cracked traces at the pad.  Anyways, it is all fixed up now.

The PCB fingers at the upper right hand corner is for a 3.3V serial connection for downloading firmware.

I replaced the header with a pairs of 3 pins rangle angle ones.  I ordered the crimping pins to make the cable using my own wires as those premade "dupont" uses poor quality wires.  I used some 2mm transparent heat shrink tubing to cover the labels which are printed with 6 points font.

Arduino ESP8266 installation

I want nothing to do with Arduino because their GPIO abstraction is plain bad.  I think direct register level access to GPIO and the official API to IP stack is all I'll need in the long run. Before I do that, I'll need to at least get the original code working first. I used the instructions from here with the following changes:

• Step 2 I used the official link because the adafruit one does not work for ESP8266.
  http://arduino.esp8266.com/stable/package_esp8266com_index.json

Not sure if this install all the needed SDK.

links: https://arduino-esp8266.readthedocs.io/en/latest/installing.html
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I wasn't too happy with the design, so I have started a new design using a STM32F103.