Z80 CPU Card for RC2014 (with clock and reset)

January 21, 2019

This is the Z80 CPU module I demonstrated a few months ago. It is designed to work with the RC2014 bus.

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So what makes it special? Well, the module includes a number of extra features and enhancements designed to simplify a system build. These include:

It will work with either the standard RC2014 bus or the latest enhanced bus where all the Z80 CPU signals are available.

It includes several options for generating a signal clock: Crystal, Oscillator or taken from RC2014 back plane.

A reset circuit is included.

And the signals INT, NMI, BUSRQ and WAIT feature 10K pull-up resistors.

The schematic is here:

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and you can find it on Tindie here:

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8052 CPU card for RC2014 Bus part 2

December 31, 2018

It’s been a while since I posted about the 8052 CPU card for RC2014 Bus and heres a update to where i got to with this interesting RC2014 project.

The original 8052’s are still available but originally used UV erasable EPROM or OTP PROM for their program memory. So instead I’ve been using a modern FLASH memory version of the 8052, a AT89C5252 with great success.

The original 8052-BASIC has was good but had a number of software bugs. Fortunately, there had been a number of improvements over the years and the version I’ve been using is V1.31 which can be found here:

8052-BASIC needs a couple of K’s of RAM to operate. For this I’ve been using a standalone 32K-byte SRAM card.


Common TTL and CMOS Logic Gates

November 26, 2018

I been using a lot of TTL and CMOS logic gates in my recent RC2014 circuits and after realising that I had loaned out my much used copies of TI’s TTL Logic data books some time again and never got them back so to help me I created this quick comparison table for the common TTL and CMOS logic gates.

For completeness here’s a logic truth table:


eDay7

October 31, 2018

We were at eDay again earlier in the month (Saturday 6th October 2018) as part of Newcastle Maker Space. This is the seventh year its been going and as usually we had a great time showing off various projects.

We had the following R-Kade and PiZythn and Rc2014 projects on show.

For those who don’t know what eDay is: eDay is a local digital skills day where various digital technologies are demonstrated to an enquiring general public. A sort-of geeky show and tell where local groups and individuals meet at Gateshead Central Library and show off their projects or what interests them.


No more Maker Faire UK

October 3, 2018

It was with great sadness that I read that Maker Faire UK will not be coming back next year.

The venue Centre for Life in Newcastle has hosted the maker event since 2009 and was the very first venue to host a Maker Faire outside of the United States.

I’ve been a regular visitor and exhibitor since 2010 and enjoyed every moment of my time at it.

Fortunately, there are still plenty of other Mini Maker Faire’s in the UK and I’ll hopefully be visiting some of them next year instead.

 

So a final thank you to Maker Faire UK, to the people who organised it, to the exhibitors who showed off many great projects and to the many visitors who came to see what it was all about.

 

Here’s the message from Maker Faire UK web site:

Important news

In 2009, Life Science Centre brought Maker Faire to the UK and has hosted the country’s flagship event ever since. Over that time, the popularity of making activities in the UK has sky-rocketed.

Life is proud to have been pioneers in this growing Maker movement, but we feel the time is right to make a change and to bid a fond farewell to Maker Faire UK. Lovers of all things making needn’t fear, as we’re opening a new space in Life Science Centre dedicated to crafting, tinkering and creativity in the spring of 2019.


Raspberry Pi Hardware GPIO Shutdown

September 12, 2018

I found this snippet of knowledge from the Raspberry Pi forum the other day when searching for a easy way to shutdown a RPi from a simple push button.

Open /boot/config.txt in your favorite Raspbian editor and add the following line:

dtoverlay=gpio-shutdown,gpio_pin=7

You may need to add a pull-up resistor to the GPIO pin or add the instruction gpio_pull=up to the instruction. You can also leave out the gpio_pin and the system will default to GPIO3.

You can also monitor the RPi’s status by adding this line to config.txt:

dtoverlay=gpio-poweroff,gpiopin=27,active_low=1

GPIO27 will be high to indicate when the RPI is running or low when it is shut down.

There is more detailed information here:
https://www.raspberrypi.org/forums/viewtopic.php?t=221997
https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README


8052 CPU card for RC2014 Bus

August 31, 2018

A few months ago I mentioned a 8031/8052 CPU card I had designed for the RC2014 bus. Here’s a couple of pictures for an assembled card. I’m just starting to test it out so I will post results shortly.