๐ฌ๐ง Minstrel 4th (Jupiter Ace Clone): Part 2 (SD Card Interface) [TCE #0602]
26Let's build the Jester Ace, an SD card interface for the Minstrel 4th, designed by Ian Johnson. It will allow us to load TAP files (see note below) from an SD card rather than having to convert them to WAV and load them like a cassette.
I got it a few years ago - mine is a v1.1 board with v2.2.4 firmware.
They were available from Ian's Tindie store but are unfortunately out of stock at the moment (8-May-2025):
https://www.tindie.com/products/dr_ian_johnson/jester-ace/
It was pretty easy to build and worked without hassle - once I'd inserted a micro SD card ... won't do nuthin' if one isn't inserted.
As my Minstrel 4th has stand-offs, the Jester Ace felt a bit wobbly - I solved this by drilling a 3.5mm hole in a track-free part of the board and installing its own stand-off. Now nice and stable.
It requires the TAP files to have a v2 header that is 27 bytes in length - this includes an additional "program type" byte that 26-byte TAP file headers don't include. If the TAP file has a 26 byte header you'll get an "error 10" when trying to load, even though the TAPLS.PY script doesn't flag a problem.
This meant that programs I got from George's repository (link below) like Tut-Tut, Valkyr and 3D Monster Maze wouldn't work initially.
I solved the issue by using some of Ian's Python scripts on his Github to convert the TAP file to TZX format, and then back to TAP format ... now with a 27 byte header.
Ian also has a Github repository related to the Jester Ace:
https://github.com/ianjohnson/jesterace
00:00 ... Intro
02:35 ... Board is built
05:20 ... Adding extra stand-off
06:38 ... First test
14:45 ... TAP file header problem
17:45 ... Loading Valkyr
24:54 ... Loading 3D Monster Maze
30:20 ... Changing directory on the SD card
33:35 ... Loading Tut-Tut
38:36 ... Channel thanks & Outro
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From Part 1:
The Minstrel 4th is a Jupiter Ace compatible computer from Dave Curran at Tynemouth Software. It's part of a series of computers that Dave has designed and refined over the years, including the Minstrel 2 (ZX80), Minstrel 3 (ZX81) and MiniPET.
As it's a Jupiter Ace it runs Forth natively, something that has always intrigued me. It also has an RC2014 interface which gives it a lot of expandability.
Dave co-incidentally re-launched this machine today - check out all the details on his blog post:
http://blog.tynemouthsoftware.co.uk/2025/05/minstrel-4th-returns.html
I got the kit a few years ago - mine is v4.28.
It only took a few hours to build and worked straight away. The power connection is a little flaky but that's my fault - rather than using the dependable 2.1mm DC jack that Dave included in the kit I decided to use a fancy one with built-in ON/OFF switch. I shall be switching to the simpler jack.
Loading software via the tape interface wasn't too difficult but required a few tweaks for it to work for me using my 2012-era Mac mini server as the "cassette player":
[1] Use the mame-castool with "jupiter" format to convert TAP files to WAV, and then, using Audacity,
[2] Apply an 8kHz LPF to the audio, and
[3] Bump the volume up by +10dB
Not surprisingly, there is a post on Dave's blog about this:
http://blog.tynemouthsoftware.co.uk/2020/05/loading-programs-on-minstrel-4th-or-jupiter-ace.html
Dave's Tindie store:
https://www.tindie.com/stores/tynemouth/
George's Jupiter Ace repository:
https://github.com/markgbeckett/jupiter_ace
New software on tape for the Ace/Minstrel 4th from Cronosoft - 3DMM (3D Monster Maze) and Tut-Tut:
https://cronosoft.fwscart.com/
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https://karlcasey.bandcamp.com/
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