Sign in to follow this  

JTAG Logic Analyzer

Recommended Posts

Hello everyone,,

Ok, I went down the rabbit hole and am just now coming up for breath!


After an epic week long battle that found me obsessed with this one task I have something pretty cool working on the Papilio.


Let me start from the beginning, at the end of last week when I was working on the new board design I realized that there might be a huge problem with trying to connect the channel A UART pins from the FT2232 to FPGA I/O pins. I pulled out the trusty Papilio One and tested it out, sure enough, when the Papilio is being programmed all of the I/O pins go to 3.3V which will interfere with the TCK and TDO pins during jtag programming. So the way I had things wired up was not going to work. I started thinking about solutions, adding an IO switch would solve the problem but I'm not super thrilled about doing so. So I started thinking about why we need it connected and it really comes down to being able to use channel A for communications after the FPGA is programmed. Well, we already have an example of doing that, we use the bscan primitive to program SPI Flash...

app marketing strategy

So I thought, well before I commit to adding an IO switch to the board I should spend a couple days connecting the Sump Logic Analyzer to the bscan primitive so we can use the FT2232 channel A or logic analyzer debugging and use channel B for normal uart communications to our Soft Processor. It's going to be hard to do but I should be able to bang it out in a couple days... Famous last thoughts...


Every day I made just enough progress to keep me completely obsessed for the next day, just a little bit more and it will be working... Well it dragged on way longer then I expected but I have a first working prototype! There are still some bugs to squash but it is working well enough to prove that we can use channel A for debugging and there is no need to add an IO switch to the new board

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this