ledramp user manual

Title	ledramp-s3esk (LED ramp effect)
Author	Nikolaos Kavvadias (C) 2014, 2015, 2016 (Modifications/ additions)
Source	User "buserror" (C) 2007
Contact	nikolaos.kavvadias@gmail.com
Website	http://www.nkavvadias.com
Release Date	08 August 2016
Version	1.0.3
Rev. history
v1.0.3	2016-08-08 Update file names, add GHDL simulation scripts.
v1.0.2	2016-07-10 Update for 2016.
v1.0.1	2014-06-18 Changed README to README.rst; COPYING to LICENSE.
v1.0.0	2014-06-09 Initial release for the Spartan-3E Starter kit board.

1. Introduction

ledramp is a "Knight Rider" style LED ramp effect, which uses two complementary PWM phases for consecutive states. Essentially the first state (PULSE) is a counting state lasting for 0.1 sec. The second state, SHIFT, is where the actual shift (left or right) is applied and the boundary conditions (for the leftmost and rightmost positions) are taken into account.

This version of the design directly uses the 50 MHz clock source available on the Xilinx Spartan-3E starter kit board.

The design has been adapted from this known original source: http://www.avrfreaks.net/index.php?name=PNphpBB2&file=printview&t=54866&start=40

2. File listing

The ledramp distribution includes the following files:

/ledramp-s3esk	Top-level directory
AUTHORS	List of authors.
LICENSE	3-clause modified BSD license.
README.rst	This file.
README.html	HTML version of README.rst.
README.pdf	PDF version of README.rst.
clean.sh	A bash script for cleaning simulation artifacts.
ghdl.mk	Makefile for VHDL simulation with GHDL.
ghdl.sh	Bash shell script for running the simulation with GHDL.
impact_s3esk.bat	Windows Batch file for automatically invoking Xilinx IMPACT in order to download the generated bitstream to the target hardware.
ledramp.ucf	User Constraints File for the XC3S500E-FG320-4 device.
ledramp.vhd	The top-level RTL VHDL design file.
ledramp_tb.vhd	Testbench for the top-level RTL VHDL design file.
ledramp-syn.sh	Bash shell script for synthesizing the ledramp design with Xilinx ISE.
rst2docs.sh	Bash script for generating the HTML and PDF versions.
xst.mk	Standard Makefile for command-line usage of ISE.

3. Usage

The ledramp distribution includes scripts for logic synthesis automation supporting Xilinx ISE. The corresponding synthesis script can be edited in order to specify the following for adapting to the user's setup:

• XDIR: the path to the /bin subdirectory of the Xilinx ISE/XST installation where the xst.exe executable is placed
• arch: specific FPGA architecture (device family) to be used for synthesis
• part: specific FPGA part (device) to be used for synthesis

3.1. Running the simulation script

This step assumes that the GHDL executable is in the user's $PATH, e.g., by using:

$ export PATH=/path/to/ghld/bin:$PATH

Then the simulation shell script can be run from a UNIX/Linux/Cygwin command line:

$ ./ghdl.sh

This will produce a text file named ledramp_results.txt with the values of current time whenever a clock event occurs (as integer) and the signal ramp.

To clean up simulation artifacts, including the generated diagnostics file, use the clean.sh script:

$ ./clean.sh

3.2. Running the synthesis script

For running the Xilinx ISE synthesis tool, generating FPGA configuration bistream and downloading to the target device, execute the corresponding script from within the ledramp-s3esk directory:

$ ./ledramp-syn.sh

In order to successfully run the entire process, you should have the target board connected to the host and it should be powered on.

The synthesis procedure invokes several Xilinx ISE command-line tools for logic synthesis as described in the corresponding Makefile, found in the the ledramp-s3esk directory.

Typically, this process includes the following:

• Generation of the *.xst synthesis script file.
• Generation of the *.ngc gate-level netlist file in NGC format.
• Building the corresponding *.ngd file.
• Performing mapping using map which generates the corresponding *.ncd file.
• Place-and-routing using par which updates the corresponding *.ncd file.
• Tracing critical paths using trce for reoptimizing the *.ncd file.
• Bitstream generation (*.bit) using bitgen, however with unused pins.

As a result of this process, the ledramp.bit bitstream file is produced.

Then, the shell script invokes the Xilinx IMPACT tool by a Windows batch file, automatically passing a series of commands that are necessary for configuring the target FPGA device:

1. Set mode to binary scan.

setMode -bs

2. Set cable port detection to auto (tests various ports).

setCable -p auto

3. Identify parts and their order in the scan chain.

identify

4. Assign the bitstream to the first part in the scan chain.

assignFile -p 1 -file ledramp_s3esk.bit

5. Program the selected device.

program -p 1

6. Exit IMPACT.

exit

4. Prerequisites

• [suggested] Linux (e.g., Ubuntu 16.04 LTS) or MinGW environment on Windows 7 (64-bit).
• [suggested] GHDL simulator: http://ghdl.free.fr The 0.33 version on Linux Ubuntu 16.04 LTS was used.
• Xilinx ISE (free ISE webpack is available from the Xilinx website): http://www.xilinx.com. The 14.6 version on Windows 7/64-bit is known to work.