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Acorn System 1 Memory Board and Dataman programmer update

10/6/2020

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Last week I'd had enough of that Dataman programmer. It would sometimes work but more often that not Windows would fail to recognise the programmer. I'd tried it on Windows XP and three different Windows 10 machines (one was a brand new out the box machine) and it was always the same. So I sent their tech support people an Email saying fix it, or they were getting it back. I got a lovely immediate reply suggesting I download the latest software from their site, which I did (even though the version I had was only two weeks old), and hey-presto, problem sorted. Have used the programmer several times and it's worked perfectly each time. 

I've also been working on my Acorn System 1 storage expansion card; and I needed a working EPROM/EEPROM programmer so I could flash an EEPROM that contains the boards memory map.
Picture
Whilst it looks like just a jumble of wires, it does work, so far, and I'm rather proud of it.
The CPU simulator on the right is designed to allow me to wiggle all the Address, Data and Control signals. It makes it really easy to set up known signal patterns to a project under test, and then poke around with a scope lead and see what's going on. It connects to the breadboard via a ribbon cable which can be removed, allowing the project to be hooked to a special expansion card that plugs into the computers backplane. 
There will be a full breakdown of how this board works (assuming it does work) soon, but in brief the board contains RAM and EEPROM which are both broken into pages. When completed the card will occupy around 56K of space in the memory map, but will contain around 8Mb of EEPROM/RAM that can be brought in and out of the map as pages.
The two, two digit LED displays on the left show the page numbers for the RAM and EEPROM. The Two digit display at the tope of the board shows the offset that is applied to the memory to allow access to the right page.
All the buffering and decoding logic, as well as some debugging displays/leds etc are on that breadboard including a flash memory that is used to calculate the offsets into the EEPROM/RAMs. The only two components that are missing are the actual EEPROM and RAM chips. They get added next and then I'll find out if this actually works. 
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Breadboard wiring aid tool

1/5/2015

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I received an Email from some kids at Stanford University in the USA about their Kickstarter project for a tool to aid with cutting wires and component leads to the right length when breadboarding.

I's a really nice, simple idea.
You can watch a short video presentation here.

https://www.kickstarter.com/projects/1094241997/ohmkara-breadboarding-multitool-electronics-protot

Good luck guys.


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Bat detector

25/4/2015

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I've added breadboard construction details for my bat detector mentioned some time ago. Breadboard documentation software is getting better all the time and after a recent search I found a pretty good one to play with, but it's far from perfect. It's a pig for example to create new parts and whilst the existing library is pretty good but it's by no means complete.


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Breadboards – Great, till they go wrong

16/5/2012

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Using breadboards, I often build project prototypes in stages as it makes sense to prove that each section works before moving on. I’ve just started another project and was confused as to why a part of it wouldn’t work. At first I suspected faulty components but ruled that out. After using my logic analyser to check the data flowing and convincing myself that the software was ok I was at a dead end. It was by pure accident that I found that one of the sockets on my breadboards is faulty.

This is one of my oldest breadboards and has given me many years of service, but it looks like it may be time for the scrap heap.

The video shows that the spring loaded contacts beneath the hole won’t grab a piece of wire.

I’ve never had a socket fail before like this, so, in future this is something that I will keep my eyes open for.
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Breadboard +5v PSU carrier PCB

15/1/2012

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I've added a new construction project for a plug-in PCB module for breadboards.
It allows one of those cheap and nasty plug-in mains transformer type PSU to be used as the power source for a +5v regulated PSU thats suitable for powering PIC, TTL/CMOS logic and other circuits.
Because there's no direct electrical connection to the mains, it's perfectly safe for beginners to create. You can also throw one of these together for less than £2.00

If anybody in the UK is interested, I've got a couple of blank, etched and drilled PCBs that I'll give away on a first come, first served bases. All I ask is for £1.00 to cover my postage and packing costs. All you need to find are the 13 components to assemble the thing.
Picture
Plug-in Breadboard regulated +5v PSU
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    A software and hardware engineer who loves retro computers.

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