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Posts: 19
Registered: ‎04-26-2008

Interfacing VHDL code to picoblaze, display on spartan 3e lcd display

OK, I've been working on a simple project (simple until now) where I want to use the spartan 3e board to take temerature data from a digital thermometer hooked into the board.  My goal is to display the data on the LCD screen of the spartan board.  So far, I found a verilog written top module which I've modified to use picoblaze and display words that I coded directly into the software.psm file.  Sooo....that thing works, but I've hard coded what to send to the lcd display directly into the software.psm file.  The data being send from the digitial thermometer is an 8 bit word....so, any ideas how to feed this 8-bit word into the picoblaze processor?  It really has me confused.  Any ideas on where to start would be appreciated.


BTW, this picoblaze thing is really, really, really cool!  I'm by no means an expert with this stuff (I'm an electromagnetics guy), but this stuff is a real lot of fun to mess with.  Thanks for any help offered.



Posts: 19
Registered: ‎04-26-2008

Re: Interfacing VHDL code to picoblaze, display on spartan 3e lcd display

I'm replying to my own message, but I'm OK with that. I found Ken Chapmans pdf document explaining this process.  It sucks, because the problem I'm trying to work out is something he says, "Exercise – Implement a hardware based state machine which obeys the timing requirements for an 8-bit write of data including the 40μs delay. Modify the

PicoBlaze interface and code to use your hardware circuit to write to the display. Under what circumstances would this approach be useful?"


That's funny, I can tell you right now that it would be useful because then I could move forward with what I'm trying to accomplish...just kidding around here.  The document kind of answers my question, so I'll try to hack my way through this.

Posts: 1
Registered: ‎03-24-2010

Re: Interfacing VHDL code to picoblaze, display on spartan 3e lcd display

the same task is what i am also holding these days as a part of my project and addintionally, i am also trying to send the LCD data to pc via the RS232.

so i'm also seaching for the code for this part. will you share your code and problem for this project?

will be greatful for this, if.

Xilinx Employee
Posts: 754
Registered: ‎09-05-2007

Re: Interfacing VHDL code to picoblaze, display on spartan 3e lcd display

What you have probably discovered is that when you make a relatively complex state machine dedicated to a task it is then tricky to make it flexible without it becoming bigger, and more significantly, so complex that you begin to fear that you will break it! In which case to have recognised one of the fundamental strengths of any processor including PicoBlaze.


The fact that PicoBlaze is small and flexible with a naturally sequential programming language just means that is often a way to convert the high performance hardware fabric of an FPGA into something much more usable when performing relatively slow but complex tasks. That is one reason why so many people end up with several PicoBlaze in a design; each performing just one or a few tasks in isolation such as the control of an LCD display.


The following reference design performs a set of tasks very similar to what you want to achieve…




PicoBlaze Processor Amplifier and A/D Converter Controller
Demonstrates the fundamental operation the Linear Technology LTC6912-1 programmable gain amplifier and the Linear Technology LTC1407A analog-to-digital (A/D) converter.  The results are displayed on the character LCD screen.  The SPI-based communication to the amplifier, the A/D controller, and the LCD screen is performed using the PicoBlaze processor controller.



Ken Chapman
Principal Engineer, Xilinx UK