RC2014 a simple ROM/RAM card

July 12, 2020

It’s been a while since we published any thing new for the RC2014 architecture.

This is a simple combined ROM and RAM card designed to work with the RC2014 bus. This is an experimenters board. There is no fancy memory paging etc., it’s simple memory architecture was designed to be flexible and allow the user to experiment with other CPU architectures on the RC2014 bus. It was originally designed to work with our 8052 CPU.

It features

  • enhanced RC2014 bus
  • Selectable memory* options 8K, 16K or 32K
  • Board can be used as RAM only or ROM only or both.
  • Options for nMRD/nMWR or nRD/nWR signals
  • Option for 27C512 with Hi/Lo ROM (A15) select
  • IC Decoder 74xx138 using A15/A14/A13 (with extra options for A13 & A14)
    8 or 16-bit wide data bus**
  • moveable memory positions (i.e. ROM can be at top or bottom memory space)

A couple of important notes:
* Both ROM and RAM memories must be the same size.
** see explanation below

The option for either nMRD and nMWR (nRD and nWR or’ed with nMREQ) signals or nRD and nWR only signals when IC3 (74xx32) is fitted or not fitted allows for experimenting with other CPU Read/Write architectures.

Notably, the enhanced RC2014 bus features a 16-bit data bus. The card can use this enhancement by allowing the selection of the high or low 8-bit portion of 16-bit data bus. This allows the user to experiment with 16-bit CPU’s such as 68000 or 8086 when two cards are used together.

It’s schematic is here

RC14_MEM_RAM_ROM_PCB1RC14_MEM_8052_RAM_Module_smRC14_MEM_RAM_ROM_Module_sm

 


Microchip Power Electronics Application Notes

June 25, 2020

I’ve always found application notes to be great places to expand your knowledge and understanding. Microchip have released or rather re-released a handful of power electronics related notes this month:

Advanced IGBT Driver Application Manual
https://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en1002313

High Frequency Resonant Half Bridge
https://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en1002291

IGBT Tutorial
https://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en1002315

Introduction to MOSFETs
https://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en1002293

Introduction to Rectifier Bridges and Dual Diodes
https://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en1002781

Introduction to Rectifiers
https://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en1002294

Latest Technology PT IGBTs vs. Power MOSFETs
https://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en1002316


Coronavirus and the Maker Community – a small update

May 11, 2020

A short, if belated update to how the maker community is helping tackle to Coronavirus. Again these are just some links that I spotted during normal web browsing.

The Big List: Make These Projects to Fight COVID-19 Right Now

Can You Really Sterilize A 3D Print? Real Answers From Actual Studies

The Big List: Make These Projects to Fight COVID-19 Right Now

Click to access Guide_to_Local_Production.pdf

https://www.rs-online.com/designspark/do-you-have-a-3d-printer-you-can-help-to-fight-covid-19

https://www.rs-online.com/designspark/medtronic-shares-pb560-ventilator-specifications-design-files-bom-and-cad

Makers Wanted: Fix These Medtronic Ventilator Schematics

https://gitlab.com/sethhillbrand/openventilator

https://gitlab.com/openventilator

https://www.tomshardware.com/news/raspberry-pi-ventilators

MIT Emergency Ventilator (E-Vent) Project

Raspberry Pi powered Ventilators and 80+ Open Source Ventilators Listed & Ranked

https://forum.arduino.cc/index.php?board=144.0

https://www.rs-online.com/designspark/ventilator-solutions-from-stmicroelectronics


Coronavirus and the Maker Community

April 3, 2020

It’s not very often that I comment on current events but the Coronavirus or COVID-19 or SARS-Cor-19 is too big a world event not to have some views about. As a maker and also a professional (cough) engineer I’ve been intrigued by the maker community’s response to these events. We’ve seen makers use their faculties to make face masks and face shields using 3D printers, sewing machines etc. not for themselves but for their wider local community and their local health professionals to help protect others against the spread of the virus.

There are many makers and maker companies that have been very proactive in this, just naming a few, companies like Adafruit have lead the way and their blog has many posts. Other useful sites I found are:

How to Make Plastic Face Shield with Household Materials

Face Mask Pattern (FREE) – How to Make Diy Mouth Mask

https://grabcad.com/library/coronavirus-flu-reusable-mask-1

NanoHack, an open-source 3D printed mask against COVID-19

NIH Approved 3D-Printed Face Shield Design For Hospitals Running Out Of PPE

Automating Hand Sanitizer — If You Can Find Any

Handwashing Timer Makes Sure the Suds Stay On Long Enough

https://www.deeplocal.com/scrubber

Maker communities such as Hackaday and Instructables also have many useful posts. As well as the blog entries themselves, the various comment section are full of very interesting points made by reverent professionals, as well as interesting details and suggestions by other interested parties. Below is a short list of some of the other links found:

Ventilators 101: What They Do and How They Work

Ultimate Medical Hackathon: How Fast Can We Design and Deploy an Open Source Ventilator?

https://www.opensourcemask.com/en

https://github.com/rune1234/DIY-respirator

Home

https://www.thingiverse.com/thing:4192643

http://forums.parallax.com/discussion/171398/coronavirus-open-source-ventilator-real-time-monitoring-system-p2-challenge

https://panvent.blogspot.com

https://www.instructables.com/id/The-Pandemic-Ventilator

Professional Ventilator Design Open Sourced Today by Medtronic

Makers Wanted: Fix These Medtronic Ventilator Schematics

Ultimate Medical Hackathon: How Fast Can We Design and Deploy an Open Source Ventilator?

https://edition.cnn.com/2020/03/23/us/coronavirus-3d-printed-medical-supplies-trnd/index.html

In addition, many universities and other groups have also proposed alternative equipment designs and builds:

https://oxvent.org

Open source medical ventilator for COVID-19 patients

http://news.mit.edu/2010/itw-ventilator-0715

MIT Develops Cheap, Open Source Ventilator for Coronavirus Treatment

MIT Emergency Ventilator (E-Vent) Project

Home-EN

Click to access DRM127.pdf

Scientic and Medical Journals and Articlas:

Click to access DMD_2010_Al_Husseini.pdf

https://journals.lww.com/ejanaesthesiology/fulltext/2008/02000/optimal_ventilator_settings_in_acute_lung_injury.1.aspx

Click to access 20190336713.pdf

Standards and Regulation

https://www.bsigroup.com/en-GB/topics/novel-coronavirus-covid-19/ventilators

https://www.cencenelec.eu/News/Press_Releases/Pages/PR-2020-003.aspx

And finally, its also the call to arms by many governments to their countries biggest or best industrial companies to help eleaviate their medical equipment shortages. The mainstream media have been quick to jump on these stories of Formula 1 teams, big defence and big consumer companies banding together to rapidily design and manufacture the much needed medical equipments. Others have asked why their countries are not doing the same or enacting war time or emergency powers to allow manufactures to quickly add their manufacturing might to the effort.

https://www.gov.uk/government/publications/specification-for-ventilators-to-be-used-in-uk-hospitals-during-the-coronavirus-covid-19-outbreak

https://www.fda.gov/medical-devices/letters-health-care-providers/ventilator-supply-mitigation-strategies-letter-health-care-providers

https://www.medtronic.com/us-en/e/open-files.html

https://github.com/abetusk/Medtronic-PB560-Ventilator-System

https://www.bbc.co.uk/news/health-52087002

https://www.cnet.com/roadshow/news/mercedes-amg-f1-ventilator-cpap-covid-19/

https://docs.google.com/spreadsheets/d/12IGXL9XweZImqYcS8V8zFWNDV50q5R0eZECRalwTo7E/edit#gid=0


Starting with Raspberry Pi Bluetooth & Python

March 25, 2020

I recently started doing a small fun project with a RPi and a BT enable remote controlled car. (Dagu Racer 1) when I hit some problems with writing Python code to connect to the RPi’s BT.

After some web browsing and a bit of trial and error I found the following application updates and library installs got things working.


sudo apt-get update
sudo apt-get install bluetooth bluez libbluetooth-dev
sudo python3 -m pip install pybluez

For the Python code


import bluetooth

# Bluetooth stuff
bd_addr = “20:13:05:30:01:14”
port = 1
sock = bluetooth.BluetoothSocket( bluetooth.RFCOMM )
sock.connect((bd_addr, port))

# 0x1X for straight forward and 0x11 for very slow to 0x1F for fastest
sock.send(‘\x1A’)


P2 ES evaluation system prototype wings

February 26, 2020

Last year Parallax released their latest multicore processor, the Propeller2 or P2X8C4M64P to give it, its full name. It’s been a very long time coming and after a few setbacks it is finally here. It’s specs are very good, featuring 8x 32-bit cores (or cogs as Parallax likes to call them), 512K RAM and 64 GPIO with SmartPin features.

I got my P2 evaluation system (ES) board a few weeks back and designed a couple of P2 ES prototyping wings to go with it.

The first prototyping wing (on the right) is a classic proto board with I/O from two GPIO ports. The other prototyping wing is a breadboard design for faster circuit build and test and features a 3x LED’s and 2x switches

I’ve got a few spare PCB’s which I’ll put on my Tindie store.


Big box of PCB’s

January 30, 2020

This week saw the arrival of another big box of PCB’s. A lot of PCB’s. Some old but many new.

Arriving where some new stock of RC2014 prototype board, prototype plus boards and extender boards which I sell on Tindie.

Also in the box where some new board designs. No new RC2014 PCB’s this time but some boards for the ZX Spectrum and Commodore 64 computers. I’ll share more details of these in the coming days and weeks.

Time to break out the soldering iron 🙂

Here’s my Tindies store.


ZX Spectrum Projects – Data Storage

December 31, 2019

When the ZX Spectrum came out in 1982 the options for data storage on home computers were very limited. You usually had the choice of audio cassette tape or floppy disk. The ZX Spectrum initially came with audio cassette storage via an external cassette player/recorder. Sinclair Research would develop a variation of tape storage in their microdrive system via their Interface 1 add-on and it was only very much later that floppy disk storage would appear as a add-on option (i.e. DISCiPLE drive) or as a official computer model (the ZX Spectrum +3)

Now, lets fast forward to the present. Audio tape cassettes and floppy disks are very much a thing of the past and getting new blank tapes or disks is difficult to almost impossible.

However all is not lost as the retro community has been very busy in the intervening years and has come up with many alternatives to tape and disk storage. These alternatives are usually based on either Compact Flash or SD-Card. Below is a short list of some DIY projects:

“Everdrive”/DivMMC for Spectrum list
View at Medium.com

SD-Card interface round-up
http://www.retroisle.com/general/sdcard_roundup.php

ZXMMC+ (sd-card access, IF-1 – RS-232 and Network), 1MB ram/rom, Kempston joystick
http://www.probosci.de/zxbada/zxmmcp/index.html

ZXcard DIY SD/MMC interface

ZXcard DIY SD/MMC interface


https://easyeda.com/sundbyk/ZXcard_II-234ad2c853054ed68d318ca9ed6dcd9f

maxduino – Unified firmware for tzxduino and casduino
https://github.com/rcmolina/MaxDuino_v1.53

TZXDuino
http://arduitape.blogspot.com/

TZXDuino-Uploader
https://github.com/rickyelqasem/TZXDuino-Uploader

Tapuino-Reloaded – A reworked smd version of the Tapuino Mini Pro.
https://github.com/arananet/Tapuino-Reloaded

TzxDuino-Reloaded – A reloaded version of the TzxDuino
https://github.com/arananet/TzxDuino-Reloaded

TZXDuino Arduino based TZX
https://github.com/StormTrooper/TZXDuino


ZX Spectrum Projects – Diagnostic & Repair

November 1, 2019

Now I’m back on my retro computers I’ve put together this quick guide for those looking to diagnose and repair ZX Spectrum computers.

Schematics and Service Manuals:

Having a set of schematics or even better a full service manual is the good thing to have before starting any repair. Fortunately for us, full schematics and service manuals for the all ZX Spectrum models are available on the web. I have my Speccy schematics printed out on the biggest paper size I’ve got access to, namely A3. The service manuals are a great place to start when looking to diagnose a fault.

Schematics and Service manuals can be found at:

World of Spectrum

Spectrum for Everyone

IC Data sheets

wikipedia
7400 series
4000 series
Zilog Z80

Diagnostic Software Tools:

Happily the ZX Spectrum has quite a few diagnostic software tools to help the would be fixer in his fault diagnostics. Most of these are based on external ROM device which avoids the need to have a fully working Speccy or the problem of loading diagnostic software from tape.

Here’s a few ROM based diagnostic tools

Brendan Alford on github has “ZX Diagnostic”

Paul Farrow of fruitcake has the following ROM tools: 128K RAM Tester & ROM Tester
he also has the official Sinclair Test ROM as well
Phil Ruston of Retroleum has the following “ZX Spectrum Diagnostic ROM”

Tools needed:

Hand tools
Side cutters
Pliers
Screw Drivers: Philips and flat blade
IC extraction tool

Soldering Iron
De-soldering tool

Multimeter

Advanced
Oscilloscope
Power Supply (Adjustable/current limited)

Diagnostic software tools (see above)

TV Monitor/Screen (or car reversing monitor for composite video)

Repair mat
Anti static wrist or foot strap
IPA Wipes (no not the beer) – Isopropyl alcohol to clean edge connectors and contacts

Good web sites:

If the your own best efforts have not yet found the problem then there several good web sites that share their repair achievements where you can search. I like the following sites:

Dave Currah of Tynemouth Software

nightfallcrew

If you’re still no wiser, then try asking on one of the various Retro Computing Forums or general electronic forums in their repair section if they have one.

Remember to share as much information about the Speccy model, what it is not doing and what you have tried so far. Avoid simple statements like “Speccy not working please help”. It goes without saying that following the forums etiquette for posting will usually get you a more productive and polite response.

World of Spectrum forums
https://www.worldofspectrum.org/forums/

These are more general forums:
atariage forums

EEV Blog fourms


ZX Spectrum Projects – HD Video output

October 28, 2019

I’ve neglected my retro computer collection for a while now, so recently I’ve been dusting off my collection, starting with the ZX Spectrum to start some new projects with them. Whilst I have a few that need repairing I quickly got distracted into wanting to make a cool project for them.

Getting the Speccy to work with modern TV’s is becoming more of a problem. I’ve made composite video modifications to my Speccys in the past, I even made a small PCB that fits into space where the existing video modulator sits. But I want to see if HD / High Definition video was possible. By HD video I mean either VGA, DVI, DisplayPort or HDMI.

A quick web search found me Victor Trucco’s TK Pie. This is an interesting way of using a Raspberry Pi Zero to provide a High Definition (HDMI) video interface to the Speccy. It uses a mix of external hardware (CPLD) and the processing power of a Raspberry Pi Zero to capture writes to the Speccy’s video RAM and convert the pixel data into HD video via the Pi’s HDMI. There’s a similar project for the BBC Micro called RGDtoHDMI.

Here’s a link Victor’s web site and TK-Pie source code files

There are couple of useful reviews of TK Pie by GozdniJezek, Building TK-Pie by Victor Trucco

and martin@8bity, HDMI output for Sinclair ZX Spectrum – TK-Pie

Some more searching found me the next two devices. They don’t seem to be DIY projects but I thought they looked interesting.
Ben Versteeg at ByteDelight has ZX-HD: The story of the ZX-HD

and also Goran Radan with his ZX-VGA-JOY