Agon Light

Any stories, collections or recollections of the earliest days of computers
or related projects
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Martin
Posts: 744
Joined: 16 Feb 2018, 14:11
Location: Warwickshire

Agon Light

Post by Martin »

It's not really retro, in that it's a new design, but it's basically a Z80 8-bit micro with a VGA output to a monitor, a PS2 keyboard connector, an audio output via a 3.5mm jack, a micro SD card slot for storage, 0.5 MB RAM, and a GPIO connector for connecting things like you would to an Arduino.
AgonLight.png
Out of the box, it runs BBC BASIC at power-on, but you can also run (or set it up to auto-run) CPM, or Forth.

The Z80 is a modern variant that runs at 18.432 MHz, and has pipelined operation so that many instructions run in a single clock cycle. It's blazing fast compared to the original Z80, and can optionally be switched into an enhanced mode with a 24-bit address bus and a 16 MB address space. It does only run at 3.3V though.

The video and keyboard are handled by an on-board ESP32. But the ESP32 doesn't have an antenna wired to it, so you can't use its WiFi and Bluetooth capabilities. Some people have complained about this being an 8-bit processor, with a 32-bit coprocessor, but it's better to think of the ESP32 as just a cheap video driver.

Olimex are now selling a clone for only €50, but if you're in the UK, you need to buy four of them (or some other gear) because Olimex won't despatch orders to the UK under €200.

I chose to buy the original board, which cost me £75 for the 'kit' version, which has all the surface-mount stuff already fitted, so only the through-hole stuff to solder myself. For £10 extra you can get the original board complete and tested.

I 3D-printed a case for mine (not my design, I used the 'official' case design, which is very neat).
AgonLightCase.jpg
All details and downloads here: https://github.com/TheByteAttic/AgonLight There are also a few interesting YouTube videos by the designer explaining this board and some of his other retro computer designs.
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Phil_G
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Re: Agon Light

Post by Phil_G »

Interesting. I had a quick read through and it's really impressive. Where did you buy the kit please Martin?
The O/S looks to be a halfway house between CP/M and MS-DOS... uses the familiar CPMTools to transfer files from a PC... but it looks like 'real' CP/M isn't quite ready yet.
It's a lovely neat board with pretty much everything you'd need, if they can get CP/M sorted..
The designer is a modest chap isn't he? ;) :
Agon light™ is the fastest and cheapest 8-bit microcomputer ever made.
(its neither the cheapest or the fastest... cheapest BASIC computer is the 'Poundshop Basic' and the MIC80 for example is nearly 3x faster)
Cheers
Phil
Martin
Posts: 744
Joined: 16 Feb 2018, 14:11
Location: Warwickshire

Re: Agon Light

Post by Martin »

I got mine from Reinhard Schu (UK). Visit this page, https://www.thebyteattic.com/p/agon.html and click on his name in the 'Get an Agon Light' section. I had to transfer the money to a bank account - which was a bit worrying - but once I had done that, the kit arrived quickly.

Reinhard was very helpful via email when initially my board didn't work properly - it was booting up, but not reading the SD card. I tried several different SD cards, all of which worked okay in cameras, Raspberry Pi, and such, so I thought there was a problem with the SD card reader (which is surface mounted, so not soldered by me). Reinhard offered to post me an SD card that he knew worked, and if that wouldn't work either, then he would replace the Agon Light. However, once I knew that the device is fussy about its SD cards, I tried some different ones, and found three that work absolutely fine. Maybe this SD card fussiness will be fixed in a future firmware upgrade: Reinhard told me that some of his other customers have experienced SD card incompatibility, and that he's considering supplying a known working SD card along with his boards.

The other option is if we could find several people who want one, we could do a bulk UK purchase from Olimex. Maybe some UK resellers will already be doing this by now, but at the time I ordered mine, the Olimex version was still not available. The Olimex version of the board is in some ways inferior (less protection on the GPIO connector, and fewer noise-reducing components on the PCB layout), but apparently it works just the same, and perhaps has a more sensible USB connector - with the original board you need a type A to type A USB lead to flash the firmware to the ESP32, or to power the Agon Light from a standard USB power supply. Most people won't have such a USB lead to hand (they are non-standard) but you can easily buy one from the usual places, or make your own by chopping and soldering together two "ordinary" USB leads.

So far, I've only run BBC Basic (Z80 version) on mine. A very impressive BASIC that has an assembler built-in. You just put the assembler instructions anywhere in your BASIC program between square brackets - and you can use labels and most other Assembler features there too. Then you can call the Assembler routines from basic with CALL or DEF FN statements. You can also use an external (PC) assembler to create programs and put the resulting files on the SD card. Of course, you could also use a C compiler to create your Z80 code.

I've been meaning to try the Forths that are available for the Agon Light, but I've not got around to it yet. I never learned CPM, but I suppose I may eventually try that too.
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Mike_K
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Location: Hertfordshire

Re: Agon Light

Post by Mike_K »

Hi Martin,

The problem you had with the MIcroSD card could have been caused by how it was formatted. I'm slowly trying to port my encoder project to STM32 and one thing I've tried to add to the prototype is a MicroSD card reader. Initially, I could not get it to work until I stumbled on a card that just worked as expected. I posted on an STM32 forum asking why this would be and was told to try formatting the cards with the official SD card formatting utility. I didn't know there was an SD card organisation, let alone a utility! After using it, most of my SD cards could be read/written to (though not all). After further reading, it seems that most "hobby level" programmers use SPI to communicate with the card readers, whereas phones, cameras, PC card readers etc use a different SDIO interface that doesn't always suffer in the same way. I guess the Agon will have used the ESP32 (or Z80) SPI interface to the SD card reader, so would suffer similar problems to me with the STM32. It's probably worth a try to re-format a card you couldn't read to see if it fixes the problem.

https://www.sdcard.org/downloads/formatter/

Mike
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