QL IO board?

[Pr0f]

Sterling work Martin - so in fact not even registered GAL needed - clever use of OE Tristate feature on the SDA line to allow it to drive or be driven!

I2C typically has pull up resistors on the bus, and devices are expected to pull down the lines when they need to change the state of them. As the MKII I2C driver was always going to be a single master on the bus - this helps reduce any complexity around SCL line.

So looking at the original ROMOEL equation you commented out - was i7 acting as a switchable input?

[martyn_hill]

Hi Prof!

So looking at the original ROMOEL equation you commented out - was i7 acting as a switchable input?

That was my guess, though on the Minne Mk2 board it is tied to 5V.

[dilwyn]

As a little aside to this discussion, I was doing a nostalgic search for the Elektor serial I/O board I built some years ago (failed to find that), and something that came up was that they have published a circuit for an I2C interface that works via RS232. It was in issue 7/2001. I failed to find a copy of that issue online - if anyone has a copy or access to a PDF, it might be interesting to see if it would be a simple and practical project for a QL.

Elektor do publish back issues, but I could only see that they are all on a USB stick which costs about €100 or £85 (and that's on half price special offer!). Some issues are available on some websites such as archive.org of course. Haven't got an account on Elektor's site to know if individual issues are available or not on there.

[ones' complement]

Incredibly simple circuit, just a MAX232 and 74LS06

hint: archive.org have Spanish copy (Sept 2001 page 30)

[Derek_Stewart]

As a little aside to this discussion, I was doing a nostalgic search for the Elektor serial I/O board I built some years ago (failed to find that), and something that came up was that they have published a circuit for an I2C interface that works via RS232. It was in issue 7/2001. I failed to find a copy of that issue online - if anyone has a copy or access to a PDF, it might be interesting to see if it would be a simple and practical project for a QL.

Elektor do publish back issues, but I could only see that they are all on a USB stick which costs about €100 or £85 (and that's on half price special offer!). Some issues are available on some websites such as archive.org of course. Haven't got an account on Elektor's site to know if individual issues are available or not on there.

Hi Dilwyn,

I have Elektor Magazines 1974 to 2019, about 23.5Gb of data.

The Serial I/O board doe not feature. I think you need to look into Every Day Practical Electronics August, September 2007 & January 2008.

QL Today March-May 2008 :

Serial IO Controller.pdf

(218.05 KiB) Downloaded 37 times

update in QL Today Vol 14, Issue 4, June-August 2010:

Oscilloscope.pdf

(93.12 KiB) Downloaded 35 times

I have made a PDF copy of the PCB overlay for the Serial I/O board, I was going to make one, but needed to produce a PCB file to get the PCB manufacturers to make a PCB.

Not sure about the copyright of the EPE magazines, I could email them if requied.

[dilwyn]

I have Elektor Magazines 1974 to 2019, about 23.5Gb of data.

The Serial I/O board doe not feature. I think you need to look into Every Day Practical Electronics August, September 2007 & January 2008.

I used to subscribe to a few electronics mags back then (I was a broadcast sound technician in those days before redundancy kicked in). So you are probably right, could have been any of the electronics mags which published computer-related projects in those days.
Thanks for the PDF - from memory, it's not that one, but that looks useful too.
I do remember they published a PCB layout, but as they wouldn't let me make a personal PCB at work (I didn't want the chemicals at home to do PCBs myself) the project I did was simple enough to build on veroboard. Me being me, I made a few simple and basic mistakes, although amazingly the board worked after correcting the mistakes without blowing anything up. I remember hunting for a dry joint for a while, and also not having fully cut a strip on the veroboard with a drill bit. Those were the days.

Speaking of Veroboard, one of the silly things I did was a "rain detector" for the clothes drying line in the back garden. Which was just a veroboard clipped to the washing line with a length of wire running through the window, and the board waited for a change of resistance when rain fell on the copper strips then we'd get some beeping noises indoors to alert us. Overkill of course, would have been far easier to do a simple self-contained circuit with a piezo speaker and a transistor or two. But I was into computers and software by then... Not long after the QL came along, I took less and less interest in electronics as time went by. Seems so long ago now.

[Pr0f]

Elektor did produce a range of I2C boards that linked together by 6 pin mini din connectors - with some sort of hub board as the main controller - I've used these with Minerva I2C.

But these days with Arduino being so well supported - there are literally dozens of interesting boards on ebay - that include the 8 port I/O using the 8574, the larger 16 channel MCP23017, the PC8591 - A/D and D/A and a host of other boards that do I2C as well (temp sensors, gyro, touch screen) - you name it, it's probably on a little module board.

[Derek_Stewart]

Hi,

The Elektor Serial I/O port was featured in Elektor November 1996, here is an extract from the magazine:

Elektor Serial IO Port.pdf

(2.65 MiB) Downloaded 40 times

I am not sure that a QL Serial port can be used like in the article, but you never know.

[Pr0f]

Those Elektor articles for I2C interface boards:

[Pepperm]

As a little aside to this discussion, I was doing a nostalgic search for the Elektor serial I/O board I built some years ago (failed to find that), and something that came up was that they have published a circuit for an I2C interface that works via RS232. It was in issue 7/2001. I failed to find a copy of that issue online - if anyone has a copy or access to a PDF, it might be interesting to see if it would be a simple and practical project for a QL.

Elektor do publish back issues, but I could only see that they are all on a USB stick which costs about €100 or £85 (and that's on half price special offer!). Some issues are available on some websites such as archive.org of course. Haven't got an account on Elektor's site to know if individual issues are available or not on there.

I have the article and the schematic is simple, however, the interface requires some DLLs that are available for Windows, PERL or Linux. Not the QL. So really just a level converter.