LEAP#337 RGB LED Glow with Opamps

For a while I’ve been thinking of ways to generate a pseudo-random rainbow glow on a composite RBG LED. In particular, while avoiding just throwing a microprocessor at the problem! I finally settled on three independent opamp-based triangle wave generators that have a nice drifting phase offset. As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub hero_image

LEAP#336 Comparator-based Relaxation Oscillator

A quick test of a classic comparator-based relaxation oscillator, modified for single-supply LM358 OpAmp. As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub hero_image

LEAP#335 MCP2200 LED Chaser (just because)

The MCP2200 USB-UART transceiver has 8 GPIO pins. Yes, you read that correctly. With such unexpected I/O capabilities, I feel obliged to do the only responsible thing: blink LEDs. Seven LED outputs and one input for a push-button to control direction of the “chase” sequence. As simple C program using the hidapi and we’re done! As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub hero_image

LEAP#334 Exercising the MCP2200 USB-UART transceiver

The MCP2200 is a USB-to-UART serial converter device. It is getting a bit on the old side, only supporting USB 2.0, and all the software support provided is Windows-only. Nevertheless, I got hold of the MCP2200 Breakout Module to find out more. I was particularly intersted to see how far I could get under MacOSX, including configuration over the HID Interface. The answer is pleasantly: all the way! As always, all notes, schematics and (more...)

LEAP#333 Measure Thy Own Voltage

One of the issues with analogue measurements on the Arduino is that typically we assume an accurate 5V reference, and need to add fudge factors for a calibrated reading. Well, I borrowed some code and re-read the ADC part of the datasheet again, and there is a neat little trick for using the 1.1V internal voltage reference to measure (thus calibrate) the supply voltage. It works, but not without caveats - so although QI, (more...)

LEAP#332 RC Phase Shift Oscillator

Three RC high-pass filter poles add more than 180˚ phase shift on top of the 180˚ contributed by a class A BJT inverting amplifier with enough gain to sustain positive feeback. And that’s all you need to make an oscillator. As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub hero_image

Reduce Proxmox LXC Backup Size and Time

Proxmox backs up guests byte-for-byte in a compressed archive. Looking at LXC backups specifically, the file system is compressed into the target backup file with just a few exceptions – temp files aren’t included. You can also add your own exceptions by editing the vzdump.conf to exclude specific file patterns. All that said, one of

LEAP#331 Getting Blinky with PIC Assembler

Not necessarily everyone’s first choice for embedded development these days, PIC is perhaps now more a right-of-passage! It was Julian Ilett who finally inspired me to try this myself. One thing that held me back was the perception that you have to “downgrade” to Windows in order to get anything going. Challenge accepted, and I quickly learned that the MPLAB X IDE is just perfect and makes PIC development on MacOSX a piece of cake. (more...)

LEAP#330 Any-to-an Polarity DC Power Adapter

I recently got a device that has a 2.1mm power connector but in centre-negative configuration. Unfortunately I don’t have any centre-negative power packs on hand. I could of course just rewire one, but decided it might be the time to make up a generic any-to-any connector. In addition to centre-positive and centre-negative output plugs, I included a 9V battery bypass and polarity rectifier, so that the input supports both centre-positive and centre-negative connections. And (more...)

LEAP#329 On DC Power Connectors

How many types of power connector is there? In addition to just two bits of wire twisted together, it is pretty much an uncountable selection! Just some notes on the main types, including bypass configurations. As always, all notes are in the Little Electronics & Arduino Projects repo on GitHub hero_image

Gitlab Runner Error: sudo: no tty present and no askpass program specified

After issuing the first build on a dynamically created Container I came across the following build error when running a command with sudo. [crayon-59847f31522f3681093998/] The error is caused by trying to run a command with sudo, however the calling user has not been authorised to use sudo. The error isn’t helpful, and doesn’t really spell out where to

Scripted Install of Oracle Java 8 on Ubuntu 16.04

Please see Install Oracle Java In Debian/ Ubuntu using apt-get for more information. [crayon-59844b9392d4e955734194/]  

LEAP#328 555 Timer VCO

The control terminal of the 555 timer can be used to adjust the upper and lower thresholds with an applied voltage. This produces a very simple voltage-controlled oscillator. The few measurements I’ve taken show that control adjustments have as much impact on duty cycle as frequency. That may be what you want … or not! As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub hero_image

Rename a Proxmox Host

Renaming a Linux server’s hostname is usually a trivial task, and that’s no Different to a Proxmox server providing it’s not part of a cluster. If your machine is in a cluster then things get a bit more complicated and that’s a blog subject for another day. For a single node machine it’s simple –

Proxmox 5.0 is now available

Today, the Proxmox VE team have released a new version of Proxmox, incrementing the major version to 5.0! The new version packs in a raft of new features, the headline being the new Replicated Storage feature which enables batch style synchronisation of local storage volumes across servers. You can download the ISO from https://www.proxmox.com/en/downloads/item/proxmox-ve-5-0-iso-installer Highlights

OBI formatting grand totals – without XML!

Recently I needed to have some conditionally formated grand total rows in OBI. I remember years ago hacking around with the XML which is far from ideal. I then realised it could be done another way, here is the example:   Create an analysis with a measure column: Apply the conditional format on the Actual

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

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

Generating Diceware Passwords in Python

Today I’m going back to a theme from a post last year and looking at generating passwords with my favourite programming language. A tweet from Simon Brunning pointed me to Micah Lee’s article at The Intercept and my first thought was to write a function to do this in Python. So here it is;

def generate_diceware_password(word_count=6):
    import random
    word_dict = {}
    passphrase = []
    with open('diceware.wordlist.andy.txt') as f:
        for line in f. (more...)

Teaching an old dog to Fish

Inspired by the recent furore around Shellshock I decided that it was time to try an alternative to bash. By the very grown up process of shutting my eyes and poking my finger at the results of a search for “shell” I ended up at fish shell, described by the project as “a command line shell for the 90s”. I’m presuming that this means the 1990s and is not a minimum age requirement.

I’m (more...)