Francis Bergin

A first go at Go

Sun, 26 Jul 2020 00:00:00 +0000

This month, I wrote a first Go program. I had played around with the features of the programming language a few times before but had never put together something actually useful. Coming from a Python background, I thought it would be useful to share my process and experience with others.

The app itself is a CLI RSS and Atom feed lister. It reads a file containing a list of feed URLs and displays the posts from the last month. In this simple project, I was able to use and understand Goroutines and Channels more in depth.

fakesocial: Fake social network using generated content

Sat, 06 Jun 2020 00:00:00 +0000

Last weekend, I released fakesocial (source code) after working on it for the last few weeks and am pretty pleased with the result. Here, I will discuss a few things about the project.

To start with, fakesocial is a simple social network consisting of fake users which have connections, make posts and also like and comment on these posts. These user profiles use generated images as profile pictures and generated text as posts and comments. The social network is then packaged as a website and served on the internet.

Execution time experiment

Thu, 30 Apr 2020 00:00:00 +0000

Consider this Python program:

# num_add.py

ans = 0

for i in range(123456789):
 ans += 1

print(ans)

It runs in a little over 10 seconds:

$ time python num_add.py
123456789

real 0m12.896s
user 0m12.868s
sys 0m0.008s

This result is expected; it takes a certain amount of time to perform more than one hundred million additions. During this, my computer was working hard; the fans started going pretty fast.

Now consider this Python program:

# sleep.py

import time

time.sleep(12.8)

print(123456789)

It executes in about the same amount of time and outputs the same thing:

watch-diff: Watch command output and get notified on changes

Sun, 01 Mar 2020 00:00:00 +0000

For a few months now, I have been using my watch-diff project to get notified on command output changes. The beauty of this simple tool is that it works with any command that can be executed in the shell. This means that once you figure out the exact command you need to monitor, you simply plug it into watch-diff and you automatically get email notifications on updates.

Example: monitoring current releases

Here is the output for monitoring the current version of this package on the PyPI website while a release is being made:

Deploying to S3 with Sourcehut

Wed, 05 Feb 2020 00:00:00 +0000

In this article, we will go through the process of automatically building and deploying this Hugo website to Amazon S3 using Sourcehut builds.sr.ht. This post assumes you already have a static website that is hosted on S3; there are plenty of guides online concerning this if it is not the case.

IAM policy for S3 bucket access

The first step is to create an IAM user with an IAM policy that can only modify the contents of the specific S3 bucket. This will ensure that if the user credentials are compromised, only the specific bucket is affected and not your complete AWS account. This is important since this user secret key will be saved on Sourcehut which is not immune to security bugs and breaches.

Commit history data analysis

Fri, 10 Jan 2020 00:00:00 +0000

In this post, I will describe the francisbergin/commit-history-data-analysis tools and results as well as a few thoughts on version control hosting and commit histories. There are many tools out there with the purpose of extracting insights from single code repositories; this one has the goal of analyzing the many repositories of a single user.

Commit aggregation

The main script found in the repository mentioned above simply outputs a git log in comma separated values (CSV) format for all the Git repositories found under a given path and for a specified author. For example, if all your repositories are under ~/code and your email is a@abc.com, you can execute the script with ./get-data.sh ~/code a@abc.com. The resulting CSV log will then be found at data/results.csv. It is also possible to give multiple emails or names; they will be prepended with --author when passed to the git command. The included git-csvlog script can be used on its own in Git projects.

Getting started with the STM32F4 and FreeRTOS

Fri, 27 Dec 2019 00:00:00 +0000

In this post, I’ll simply share a few observations on setting up a FreeRTOS project for the STM32F4 Discovery board. This guide is based on the francisbergin/stm32f4discovery repository which is fully configured and ready to use. The specific commands mentioned in this post are noted in the README or the CMakeLists files of the project.

Hardware

The STM32F4 Discovery board has the following core components:

STM32F407VGT6 Microcontroller
- 32-bit ARM Corex-M4 with FPU Core
  - ARMv7E-M Architecture
  - Thumb-1, Thumb-2, DSP, FPU (Single Precision) instruction sets
  - Single Precision FPU: fpv4-sp-d16
- 16 MHz High Speed Internal (HSI) RC Oscillator
ST-LINK/V2 used for programming and debugging
8 MHz High Speed External (HSE) Oscillator

Clock configuration

On start up, the 16 MHz internal oscillator is selected as CPU clock. Through software, we can select to use an external oscillator as clock source. This clock source is fed to a phase lock loop (PLL) which can increase the frequency up to 168 MHz. The clock is set up using the SystemCoreClockUpdate function from the system_stm32f4xx.c file. By default, for this MCU, the clock speed is configured using the HSE and PLL to output 168 MHz. However, the default HSE value is 25 MHz and so we need to modify it to 8 MHz. The PLL_M is also modified from 25 to 8. The calculation for the SYSCLK value is as follows:

About this blog

Fri, 20 Dec 2019 00:00:00 +0000

Throughout the years, I have learned a tremendous amount by reading various blogs on the internet. These are sites I regularly go to or that pop up in search results when researching a specific topic. The information I find useful ranges from low level details to high level wisdom. I believe all these sources are part of my education and I appreciate the authors very much for it. With this blog, I hope to share some ideas and insights so that other people may benefit the way I still do every day.