Thursday, February 1, 2018

a Hardware Design for XOR gates using sequential logic in VHDL

VHDL is a powerful, hardware description language.  The learning curve is steep and advanced hardware designs take many years of experience.  As an advanced C and C++ programmer with embedded hardware experience, I decided to take on the task of learning VHDL.  An FPGA board is typically needed if you intend to load your design onto a re-programmable piece of hardware.  There are many choices, from simple to complex, and from cheap to very expensive.

A few years ago, a friend recommended that I purchase an FGPA board without a hybrid ARM core to start with, as working with an FPGA board is already complicated.  Having worked with numerous ARM processors, I decided to instead purchase an FPGA board with a multicore ARM processor.  Hybrid boards such as these integrate the FPGA fabric with an ARM processor, typically multicore, over a high speed bus.  For such a configuration, the ARM processor is termed the hard processor system or HPS.  Writing to the FPGA from the ARM processor is typically performed via C from an embedded Linux  build (yocto or buildroot) running on the ARM core.

ModelSim Wave Output for the xor design
The following is a simple hardware design that I wrote and simulated in ModelSim.  Given the frequency of XOR gates in cryptography, I decided to build a simple design using XOR gates.  The sequential design is comprised of several XOR gates, XNOR'd together with a 50Mhz input clock.  VHDL components are utilized and a testbench is defined for testing the design.  The testbench for the design was loaded into ModelSim and the below image is the wave form simulation of the input signals, clock, and output signal.

The source code is available on github at the following link.
xorchain hardware design in VHDL

ModelSim Full Window view with wave form output of xor simulation. ModelSim-Intel FPGA Starter Edition © Intel

Sunday, February 12, 2017

Setting up a D-Star Access Point on Raspbian with PIXEL - Part II

This is part II of a two Part series. In part I, DStarRepeater and IRCDDBGateway were compiled and DstarRepeater was configured on Raspbian Jessie with PIXEL.  In Part II, IRCDDBGateway will be configured,and an Icom ID-51a+ will connect to the D-Star network through the D-Star hotspot.

Elizabeth Tower at the North end of the Palace of Westminster in London


Requirements


Directions


Configure ircddbgateway


Execute ircddbgatewayconfig on the target (Raspberry Pi) as follows.


pi@hbox:~ $ sudo ircddbgatewayconfig &






Replace KF5SVQ with your call sign.


Make sure that you select Save from the File Menu in order to save your changed to the configuration file.   Also make sure that you select Exit from the File menu after you select Save.

Start ircddbgateway and dstarrepeater

pi@hbox:~ $ sudo ircddbgateway &
pi@hbox:~ $ sudo dstarrepeater &



Configure the Radio 


Link to the UK D-Star Megarepeater

D-Pad -> Repeater List -> Simplex -> 145.67 DV
Press PTT
D-Pad -> Local CQ
Hold Down PTT and Talk

Setting up a D-Star Access Point on Raspbian with PIXEL - Part I

This is part I of a two Part series. In part I, DStarRepeater and IRCDDBGateway will be compiled and DStarRepeater will be configured on Raspbian Jessie with PIXEL.  In Part II, IRCDDBGateway will be configured and an Icom ID-51a+ will connect to the D-Star network through the D-Star hotspot.

Purpose


Create a hotspot or access point for a handheld radio in order to connect to the D-Star network.




Requirements





Definitions


Host - Your Desktop computer (Linux)
Target - Raspberry Pi 3 running Raspbian Jessie with PIXEL (Linux)






Directions


Write the Raspbian image to the uSD on the host.  Execute the following commands on the host.

dev@fedora:~ $ sudo umount /dev/sdb*
dev@fedora:~ $ sudo dd if=2017-01-11-raspbian-jessie.img of=/dev/sdb bs=1M

Boot the Pi with the uSD card.  Execute the following commands on the Pi.

pi@hbox:~ $ apt-get install libwxgtk3.0-dev libusb-1.0-0-dev
pi@hbox:~ $ mkdir ~/src
pi@hbox:~ $ cd ~/src
pi@hbox:~ $ git clone https://github.com/dl5di/OpenDV.git -b master
pi@hbox:~ $ cd OpenDV/ircDDBGateway
pi@hbox:~ $ ./configure
pi@hbox:~ $ make
pi@hbox:~ $ sudo make install
pi@hbox:~ $ cd ..
pi@hbox:~ $ cd DStarRepeater
pi@hbox:~ $ ./configure
pi@hbox:~ $ make
pi@hbox:~ $ sudo make install
pi@hbox:~ $ sudo mkdir -p /usr/local/etc/opendv
pi@hbox:~ $ sudo mkdir -p /usr/local/var/log/opendv


Configure DStarRepeater


Execute dstarrepeaterconfig on the target as follows.
















Replace KF5SVQ with your call sign.