LEAP#309 Audio Connectors

Audio signals can be carried by any kind of connection, but there are some more commonly used standard connectors for audio applications. I started this project folder to collect notes on the verious connectors I use or have encountered. As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub hero_image

Start/ Stop Container Using The Proxmox Web API in Bash

The Proxmox Web API can perform any actions available in the front end Web. By implementing a REST API, all commands have been exposed and can be used programatically. In this example we’ll use Bash to call the Proxmox Web API with our authentication token to start and stop an existing LXC Container. See this

LEAP#308 Combinational Logic 7-segment LED Driver

Ben Eater published a fantastic video/tutorial on designing a 7-segment hex decoder as an adjunct to his 8-bit breadboard computer quest. The first thought was of course “that’s an awful lot of work just to drive a 7-segment display .. lucky we don’t have to do that these days!” My next thought was naturally: “OK, now let’s build it!”. It was in fact a great excuse to dust off some combinational logic methods. As (more...)

Getting Started With Proxmox HTTP API Commands

Proxmox has 2 API access points that can be used to control your Proxmox server and virtual guests. One of the API access points is using the command line, which you’re likely already familiar with. The other is the HTTP web API which is exposed as part of the WEB GUI on port 8006. The

Parse Proxmox Web API authentication ticket and the CSRFPreventionToken in Bash

The Proxmox Web API can perform any actions available in the front end Web. By implementing a REST API, all commands have been exposed and can be used programatically. The API is secured using a token based method which provides a ticket that must accompany all API requests except for the request that generates the token. The

LEAP#307 Boldport Matrix Keypad Control

So… ways to get arbitrary messages onto the Boldport Club Matrix? I happen to have a KeyboardMatrixModule that is coincidentally 5 keys high by 4 wide .. a number that neatly fits into the 24x5 display port of the Matrix. So I’ve wired it up and enabled a couple of commands to edit a message and start it scrolling. It is somewhat tedious, but it works! As always, all notes, schematics and code are in the (more...)

LEAP#303 Keyboard Matrix Module

I picked up one of these 4x4 Independent Keyboard Matrix modules to see how useful it might be for arbitrary input with a microcontroller. I examine how it is constructed, and provide some examples of how to make it work: LedControl - controlling the LEDs; KeyMatrixInput - multiplexed key input; SwitchInterrupts - interrupt-driven switch input. As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub hero_image

LEAP#302 Game of Life on the Boldport Club Matrix

This is a quick and dirty implementation of Conway’s Game of Life on the Boldport Matrix, mainly to learn a bit more about using the AS1130 LED driver. As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub

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LEAP#301 DHT11 Sensor Basics

The DHT11 sensor is a very cheap and common sensor that provides readings of relative humidity (20-80% ±5%) and temperature (0-50°C ±2°C). For a first test, I’m using a simple DHT11 library from the arduino playground. As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub hero_image

LEAP#300 The Matrix LED Test

The LRAS1130 Arduino library from @luckyresistor is an easy way to get started with the BoldportClub Matrix and an Arduino. I’m using a slightly modified version of the LedTest sketch from the library here. LED test = all passing! As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub hero_image

LEAP#299 The Boldport Club Matrix

The Matrix is an I²C-controlled 24x5 LED matrix display, powered by an AMS AS1130 LED driver. It’s made of 0.2mm thick circuit board so it can slightly bend. A few can be chained together for a larger display. With 120 0805 LEDs and an SSOP-28 AS1130, this kit is another great excuse to fire up the hot-air and get a stencil from OSHStencils. As always, all notes, schematics and code are in the Little (more...)

LEAP#298 The Golden Hind

A nice diversion .. a simple kit of the Golden Hind (Model 9209) ended up in my shopping cart on an impulse. I’ve been curious about the recent popularity of these mini 3D metal models. I am guessing the availability and affordability of precision laser cutting equipment might have something to do with it. The Metal Earth brand is often seen in toy retailers (it even has its own sub-reddit!), but the model designs all (more...)

LEAP#297 CD4070 Oscillator

This is a widely-shared circuit of a “square wave generator with CD4070”. I had a few spare minutes so I thought I’d give it a go. Should be straight-forward, looks like a familiar oscillator circuit based on logic gates. Well, not so fast. I found this configuration extremely temperamental on a breadboard, and the output is more sinusoid than square. It also made me wonder about the performance of this circuit with buffered and unbuffered (more...)

Virgin Media Speeds In Nottingham

Somewhat off-topic today, but something that I’ve recorded here to showcase the current state and see if anyone else is getting similar issues. A colleague of mine and I have been measuring our broadband speeds since the start of the year. We both live in Nottingham and pay for a residential Virgin Media 200mbps line which

Simple iptables Rules for Ubuntu/ Debian VPS

The following iptables rules are are a starting point to add basic firewall security to a public facing server, such as a public VPS. The primary focus is to stop any inbound traffic other than SSH, which is required for shell access. The biggest issue with public VPS providers is that often some iptables features

Setting Memory Resource Limits With LXC

  Linux Container (LXC) management is now often dealt with by LXD, the Canonical lead project built on top of LXC. LXD offers a suite of options for controlling Linux Container resources and setting limits where appropriate. This post will talk about setting constraints on CPU, however other options are available for limiting almost any

LXC 2.x/ LXD Cheat Sheet

Here are some of the most used commands for creating and managing an LXC/ LXD host and containers. It’s assumed that you have a working environment and a privileged SSH connection to the LXC server for issuing the commands. Basics Start and Stop a LXC Container Starting out with the basics here – starting and

Setting CPU Resource Limits With LXC

Linux Container (LXC) management is now often dealt with by LXD, the Canonical lead project built on top of LXC. LXD offers a suite of options for controlling Linux Container resources and setting limits where appropriate. This post will talk about setting constraints on CPU, however other options are available for limiting almost any sort

Add systemd Startup Script For CouchDB

Currently, version 2.0 of CouchDB doesn’t come with any form of startup script. I’m sure that as the CouchDB 2 branch becomes more mature and it’s added to the various software repositories startup scripts will be shipped as standard, but until then we have to make do. The below script is a systemd startup script

Basic IPTable Rules

Here are some basic IPTable rules to enable essential connectivity from the host. Outbound connectivity such as ping, DNS and HTTP are all enabled, along with inbound SSH. All external sources are enabled for SSH so it’s advisable to restrict this further once you’re up and running. This IPTables script is intended to be a starting point