How to make a VHDL design in Ubuntu/Debian

This tutorial describes how to install all the necessary tools to develop simple designs under Ubuntu for the Armadeus Project.
As Ubuntu is a Debian based distribution, all the informations on this page should work with Debian too.

Editing VHDL

To edit VHDL code all standard editing softwares like Vim, Emacs or others can be used. But Emacs has a really good vhdl-mode used by lots of designers. If you hate Emacs, you can use the xilinx-embedded editor or vim with a VHDL-plugin under development.

Making a simple project

It's a good idea to make a clean project tree for your design, because different software are used and each generates a large amount of files.

Here is an example of a VHDL project tree :

• MySimple_project/
  • src/ for all sources files (.vhd,.ucf,.xcf)
  • testbench/ VHDL sources files for testing your design
  • ise/ Xilinx web pack will work in this directory
  • simu/ All files generated by the simulator

Simulation

To stay in the Free Software spirit, the best method to simulate is to use GHDL (based on GCC).
To install it on Ubuntu you just have to type :

$ sudo apt-get install ghdl

You can find a good tutorial for using GHDL here and on the official website. It's supposed that the project tree used is this one described previously.

Analysing files:

$ ghdl -i --ieee=synopsys --warn-no-vital-generic --workdir=simu --work=work src/*.vhdl testbench/testb_file.vhd

And compile:

$ ghdl -m --ieee=synopsys --warn-no-vital-generic --workdir=simu --work=work testb_file

After that a binary file named testb_file is created; to launch simulation we just have to:

$ ./testb_file --stop-time=500ns --vcdgz=testb_file.vcdgz 

The stop time option sets the simulation time and the vcdgz option will generate a gunzip compressed wave file to visualize the result.

Visualizing the result can be done with gtkwave:

$ sudo apt-get install gtkwave

We can launch it with the following command :

$ gunzip --stdout testb_file.vcdgz | gtkwave --vcd

It can be a good idea to make a Makefile instead of typing all this commands, here is a little Makefile:

# project name
PROJECT=bus_led_top
# vhdl files
FILES = src/bus_led.vhd src/bus_led_top.vhd
# testbench
SIMTOP = led_top_tb
SIMFILES = testbench/led_top_tb.vhd
# Simu break condition
GHDL_SIM_OPT    = --assert-level=error
#GHDL_SIM_OPT    = --stop-time=500ns

SIMDIR = simu
SYNTHFILES = bin/bus_led_ise/netgen/synthesis

GHDL_CMD        = ghdl
GHDL_FLAGS      = --ieee=synopsys --warn-no-vital-generic

VIEW_CMD        = /usr/bin/gtkwave

ghdl-compile :                                                                                                 
 mkdir -p simu                                                                                               
 $(GHDL_CMD) -i $(GHDL_FLAGS) --workdir=simu --work=work $(SIMFILES) $(FILES)                                
 $(GHDL_CMD) -m $(GHDL_FLAGS) --workdir=simu --work=work $(SIMTOP)                                           
 @mv $(SIMTOP) simu/$(SIMTOP)                                                                                
                                                                                                              
ghdl-run :                                                                                                    
 @$(SIMDIR)/$(SIMTOP) $(GHDL_SIM_OPT) --vcdgz=$(SIMDIR)/$(SIMTOP).vcdgz                                      
                                                                                                             
ghdl-view:                                                                                                    
 gunzip --stdout $(SIMDIR)/$(SIMTOP).vcdgz | $(VIEW_CMD) --vcd                                               
                                                                                                             
ghdl-clean :                                                                                                  
 $(GHDL_CMD) --clean --workdir=simu     

to use it, just write :

$ make ghdl-compile

to compile, then:

$ make ghdl-run

to run the design, then:

$ make ghdl-view

to launch gtkwave and visualize the results.

Syntesis, place & route

GUI installation

To synthesize the design it is mandatory to use Xilinx tools (It's not exactly true, others tools can be used for synthesize like Mentor tools, but at the end, to make the bitstream, Xilinx tools are mandatory), fortunately Xilinx provides his webpack for Linux. Click here if you didn't install it yet.

To launch the floorplanner, DISPLAY has to be change:

 export DISPLAY=:0

After this installation, ISE can be found in the directory $(Xilinx_root_dir)/bin/lin. To avoid retyping export, a little script launch_ise.sh can be made in bin/lin/ directory:

#!/bin/bash
export DISPLAY=:0
~/Xilinx92i/bin/lin/ise

Then make launch click :

There is a good tutorial on harded.free.fr.

Using Xilinx command line tools for shell syntesis

See Using Xilinx Webpack-8.1i on grml Linux in scripted mode, without GUI for an introduction.

First of all, library files has to be copied in library directory :

sudo -s
mkdir /usr/local/lib/xilinx/
cp Xilinx_directory/bin/lin/*.so /usr/local/lib/xilinx/
echo /usr/local/lib/xilinx >> /etc/ld.so.conf
ldconfig

Then modify your .bashrc (add at the end):

PLATFORM=lin
XILINX=Xilinx_directory
export XILINX
PATH=Xilinx_directory/bin/lin:$PATH
export PATH

Then ISE can be used in command line (xst, ngdbuild, map, bit,...). To avoid typing very long commands it can be a good idea to use a Makefile, xess.com provide a full Makefile to do this and a basic Makefile for simulation and synthesis can be found in the armadeus gitlab project: [1]. To use it modify the head and write the names of your files :

• General options

# project name
PROJECT=bus_led_top
# vhdl files
FILES = src/bus_led.vhd src/bus_led_top.vhd

• constraints for synthesis

# pin configuration
UCF_FILE = src/bus_led.ucf
# Synthesis constraints file
XCF_FILE = 

• Testbench options

# testbench
SIMTOP = led_top_tb
SIMFILES = ../apf_pkg/apf_test_pkg.vhd testbench/led_top_tb.vhd

• Simulation can stop after a given time or after an assert error (end of test for example)

# Simu break condition
GHDL_SIM_OPT    = --assert-level=error
#GHDL_SIM_OPT    = --stop-time=500ns