April 6, 2024

NAS migration and iTunes .. ugh

I recently moved our family’s personal storage from a ~14 year old QNAP TS-219P NAS to a new Synology DS224+ NAS, with roughly 2x the storage. The data migration went pretty smoothly, after a couple of false starts. I tried a “restore from USB drive” approach first. After all, both NAS types can back up to ext4 filesystems, so it should read OK, right? Unfortunately these copies take a looong time to complete, and the web UI provides no measure of progress to give confidence that it’s working.

February 24, 2024

Generating the Fibonacci sequence on a Raspberry Pi 5

Linux includes a bench calculator called bc, which can achieve remarkable arbitrary-precision results in very few lines of code. For ease of running, code can be embedded in a here document: fib.sh #!/usr/bin/env bash BC_LINE_LENGTH=0 bc -q <<end 0;1; for (i=1;i<1000;i++) {g=last;last+=f;f=g;last} end The BC_LINE_LENGTH environment variable is used to prevent long lines from being split with a \ continuation character. The -q flag suppresses the welcome prompt. The 0;1; bit just prints the first two results.

December 31, 2023

Janome Memory Craft 6000

We have this wonderful sewing machine from the mid eighties, a New Home Memory Craft 6000 - instruction book is available here. The brand is also known as “Janome”. This machine can stitch letters and symbols using microprocessor control, sewing “emojis” before that word was widely known. When it was recently powered on after a few years sat idle, it was completely inert (apart from the work light). A local sewing-machine repair place took a look, said it was blowing fuses repeatedly, indicating a fault on one or other of the PCBs.

December 31, 2023

Granite feet for PMG GB1i speakers

I still like my PMC GB1i speakers a lot. They are slim and sound great, but have one practical disadvantage in our house: our cat is heavy enough to knock them over. The relatively narrow spiked bases don’t offer much resistance against toppling. Sully, 6+ kilos .. no contest How are the steel spikes meant to “isolate” speaker cabinets from the floor, i.e. what’s the physics behind this hi-fi orthodoxy? Steel conducts sound quite well.

December 30, 2020

Amazon "Polly"

The voices (and tech) used in Amazon Alexa, are available for anyone to play with, free of charge - search for Amazon Polly. Update: Here’s the voice of “Brian” (British English) reading Lewis Carroll with the “Neural” engine setting eanbled. Jabberwocky Poem. Try Polly yourself here.

March 15, 2020

BBC Micro repairs

I seem to have collected a few old BBC Micros - approx 1983 vintage, so coming up to 40 years old. Before powering them up, I took the advice of Retroclinic and replaced the power supply X2 capacitors that are known to fail (damaging the power supply in the process). Retroclinic can also be found on eBay. Rather than use an old-style CRT, a Samsung LCD TV provides a much steadier picture, using an RGB to SCART lead such as this.

April 1, 2018

Epic Number Battles of History: Swift 3 vs Python

Swift 3 has a “decimal” number type that can represent values such as 0.3 that are inexactly represented in Double or Float types. According to this article: An instance can represent any number that can be expressed as mantissa x 10^exponent where mantissa is a decimal integer up to 38 digits long, and exponent is an integer from –128 through 127. Note this is not the same as Python’s arbitrary-precision integer arithmetic.

October 10, 2017

Windows 10 Settings - which one?

If you go to the search bar in Windows 10, and type “settings” - there are now at least three different places you might end up: The one on the left is “System Information”. It’s been around a while. You’ll notice it reports “version” as 10.0.15063. Top right, you get to from the classic Windows control panel / System. It shows we are version 10, but gives no other information.

October 12, 2016

Shure wireless in-ear monitoring system

A friend lent me their Shure PSM300 P3T in-ear monitoring system today. This is a top-of-the-line piece of kit for weekend-warrior type bands, costing over £600 for just one monitor mix. http://www.shure.com/americas/products/personal-monitor-systems/psm-300-stereo-personal-monitor-system/p3t-half-rack-single-channel-wireless-transmitter Turns out that the actual RF signal being transmitted is straightforward analog FM. A £10 USB TV stick and the free SDR# software http://www.rtl-sdr.com/rtl-sdr-quick-start-guide/ can decode the signal and play it out of the sound card output in stereo.

November 23, 2015

Differential line receiver for Behringer Ultranet

Prototype receiver circuit based on AM26LV32 chip: The MagJack - a Bel Stewart SI-52008-F has datasheet here: http://www.farnell.com/datasheets/1731561.pdf The IC cleans up the edges of the incoming signals. With some level-shifting and AC coupling, the signals are OK to pass into an SPDIF receiver.

September 7, 2015

XMOS StartKit - write performance of Sandisk memory card

Here’s a graph showing the write performance to a Sandisk Class 10 memory card. The reason for the sharp dips in performance, are that the FAT filing system has to go off and allocate a new cluster every N writes. For example 512 byte sectors, 32Kbyte clusters, means a new cluster is needed every 64 writes. Another factor on the XMOS board is whether the code is running in ‘debug’ or ‘release’ mode.

August 31, 2015

XMOS StartKit - reading and writing to SD card

Being able to read/write information from an SD card is probably the easiest way to get large amounts of non-volatile storage into an embedded project. I’m using XMOS StartKit, with the code from here The card reader is a part from Wurth Elektronik, Farnell / CPC part number CN18143 available here. The data and clock lines have 120 ohm series resistors, as this can help to absorb transmission-line reflections on the connecting wires (even though they are fairly short).