Programming Archives - Jacob N Calvert

Kernel Design: Microkernel vs. Monolithic

May 19, 2020

Motivation This hotly debated topic has been around for decades, and it is just as alive today as it was 28 years ago. The truth is, there are fundamental differences in the theory which drives the design of a monolithic kernel versus a microkernel. In this post, I will extrapolate from my knowledge of various kernel designs to explore what these two primary types are, what their features, benefits, drawbacks and implications may be. I’ll also briefly explore the extension…

Better JTAG on the Cheap with the FT232H

March 5, 2020

Jacob

Build Your Own, Programming, Projects, Systems, Testing

A couple of weeks ago I wrote a post about using the FTDI FT232R as a cheap JTAG debugger. I’ve been using it for a bit now to play with my Raspberry Pi 3B, and now that my code size has grown, the FT232R is just too slow to cut it. Here’s a breakdown: on the FT232R, the max speed I can set the adapter to is 3MHz. This has given me a transfer speed (loading via GDB) of around…

JTAG On the Cheap with the FTDI FT232R

February 4, 2020

Jacob

Build Your Own, Programming, Testing, Tools

JTAG 101 What is it? JTAG stands for the Joint Test Action Group, and the TAP or Test Access Port this group defined is one of the most (if not the most) common way to program and debug embedded devices and computers of all flavors. For the professional, JTAG devices are bountiful and usually not too much of a strain on the commercial budget. But for the hobbyist, things aren’t so peachy. A Segger J-Link EDU can be had for…

Building a Customized Linux Image for Raspberry Pi with Yocto + Docker Support

December 22, 2019

Jacob

Build Your Own, Programming, Projects, Uncategorized, Virtualization

Motivation I recently stumbled upon HypriotOS while looking for Docker-ready distributions for my Raspberry Pi 3B+. I flashed this onto and SD card and started playing around with it. It works incredibly well, but I noticed that it was built for armv7l which is a 32-bit implementation. Since the Raspberry Pi 3B+ has a 4x core Cortex-A53 which is 64 bit, I wanted to make use of the 64 bit processor! I’ve worked with Yocto before (in fact, my day…

Hacking a Smart Outlet

November 17, 2019

Jacob

Programming, Projects, Systems

IoT Everywhere Everything, and I mean everything is “smart” these days. Everyone has heard of the Internet of Things, and we are living through the emergence of some incredibly revolutionary connectivity. Some pretty cool and useful concepts have come out of it, admittedly, but there’s also some drawbacks. I really enjoy the idea of having smart outlets that I can command with my voice, and there are outlets-a-plenty on Amazon, but can I trust them? I’ve decided to use my…

Enterprise Service Buses and Middleware

March 14, 2018

Jacob

Programming

Distributed computing is the new norm. Multi-service architectures surround us daily. Our computing needs are served from many different independently operated services, and all implemented using different underlying technologies. When these independent units bring only one small service or set of services, it is called a microservice. While there is still some industry discussion about the exact properties of a microservice, one thing can be agreed upon: microservice-based systems enforce modular design by default. This begs the question, if…

Binary bit fields and flags

August 2, 2014

Jacob

Programming

If you’ve used any legacy C libraries before, you’ve probably used these things called bit fields, even if you didn’t know what they were. Bit fields are a way to efficiently store multiple boolean values in one or more bytes. If you can imagine an 8 bit integer as binary, each bit would have to be either a 1 or a 0, corresponding to an “On” or “Off” value. With just one 8 bit variable, you can store 8 on/off…

C++ 2014: auto return deduction and more!

July 15, 2014

Jacob

Programming

The new C++ standard-in-the-making codenamed C++1y, has some great new features. The most standout addition in my opinion is the ‘return type deduction’ feature which allows functions to use ‘auto’ return types that will be deduced at runtime. There are a few limits on this functionality however. Recursion can only happen if there is at least one return statement that can be evaluated to a non-auto type. For example: // this factorial works auto factorial(int i) { if(i == 0…