Putting My Foot Down

I can’t say I’m a kean games player exactly, but after receiving Call of Duty: Black Ops 4 free with my new PC’s processor, I thought I’d give the game a go. I did enjoy it for a while but I got introduced to Battlefield 5 by a friend. When I managed to take advantage of a special offer, I started to play and I found that Battlefield 5 suited my play style lots more than Call of Duty, good though it was.

Having said that, I have found that I have difficulty with certain key presses mid-battle. I needed a way that I could press a key utilising a foot switch to augment my control. I did some research and discovered that the Arduino Leonardo (or Pro Micro) had a USB interface built in and there is an Arduino library to take advantage of this, providing a way of emulating any HID input device.

I’m not the greatest of programmers, so I asked my friend Russ to help out. I showed him my code and he tided it up a bit and optimised it.

Programmable USB Foot Switch Prototype

The original prototype had four DIP switches on it to program one of four memories but I found, once the board was fabricated, that I’d made a massive error and managed to parallel all the DIPs meaning they would act in unison to produce the character code. I redesigned the board and included just one DIP switch.

The memories are saved by selecting a position with the rotary switch, setting the DIP switch with the binary value of the ASCII character you want in that memory position and pressing the ‘Program’ button. The LED flashes three times to confirm successful programming.

Once one of the four memories have been programmed, the foot switch can be depressed and the programmed ASCII character is sent to the device connected via USB. It acts like a general keyboard in that it auto repeats if you hold the foot switch down.

KiCad display of USB Programmable Foot Switch PCB

Getting the code to work correctly was a little painful, but between us, Russ and I have usable code. As with all projects on this site, after the design has been completely tested, the design files will be available for anyone’s use.

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A Real Groaner

Today, I got a chance to build up the latest version of the Morse Code Practice Oscillator, version 2.04. I had hoped that this would be the final one and I could publish all the files associated with it. But no, a mistake was made. To be honest, it was a really easy one to miss but none the less, it is there.

Micro Switch Not Connected

Micro Switch Not Connected

I had thought that I’d managed to get everything connected, and indeed, KiCad reported that there were no other connections to make. Unfortunately, I’d missed an error on importing the ratsnest that showed that a connection on the micro switch wasn’t named correctly. The DRC missed this completely, why would it spot it at all?

I will re-label the component footprint, but not until I have created a custom symbol with the usual micro switch labels, C, NO and NC for Common, Normally Open and Normally Closed. It turns out that the center pin isn’t the common connection either. The common is the contact nearest the hinge of the device. This wouldn’t have been a problem had the connections been made. However, in the interests of accuracy, I will resolve this. Lesson learned yet again, checking things over is never a waste of time!

Since this is a non-AVR project, it will appear in the non-AVR Projects section once finalised, however, I have started a new site www.ProjectVIR.com for projects that aren’t based around AVRs specifically. It will also appear there.

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It’s The Final Countdown (I Hope)

The last version of the Morse Practice Oscillator has arrived. v2.04 StAR Edition (St Richards Amateur Radio club). They look really nice, and because I took the opportunity to panelise them, I got 20 of each board.

CW Practice Oscillator v2.04 StAR Edition PCBs

CW Practice Oscillator v2.04 StAR Edition PCBs

They snap off really easily, although the corners may need a minor bit of sanding, just to finish them off to a good standard. I was pleased to find that I’d reconfigured the micro switch footprint correctly! The base boards look much better with a single pin header on each side rather than a transistor.

For these boards, I chose the more expensive DHL shipping option on the JLCPCB website. I wanted the peace of mind of knowing I would definitely recieve the boards and it wouldn’t take weeks. As it was, I waited exactly a week, and that included the fabrication time.

I will be building one up over the weekend and testing all the features in preparation to publishing the design files as an update to the project previously published on the non-avr page.

 

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More Oscillations

The Morse Practice Oscillator boards finally arrived! Sometimes I dispair my orders will ever get from China to the UK without incident. I think I may use the DHL option more often.

Anyway, having unpacked the new boards, I built the Oscillator up. No hitches, just the usual technique. Start with the low profile components first, resistors, dodes etc. And work up from there. This time, I had the base plate board to add.

Oscillator and Base Boards

Oscillator and Base Boards

Completed Oscillator and Base Board

Completed Oscillator and Base Board

Two things I didn’t fully consider; One was to leave clearance for the nuts that hold the base plate on. It is obscured in the image above, but the left hand front nut can’t be added since the Pitch potentiometer is too close. Secondly, the on board Micro Switch Morse Key is just too close to the Volume potentiometer to be useful. It works fine but needs to be moved.

I also discovered, I’d made a mess of the micro switch footprint somehow. The pins were .5mm too close to the center. I did manage to force it in by bending the pins to test the board but I have since corrected the footprint.

As expected, the oscillator works perfectly, whether it be monitored with earphones via the socket, or have a speaker connected to the output header. The LED for visual comms is a little dim but I suspect that a regular LED (rather than right angled) might be a better bet. I’ve yet to test this.

Meanwhile, I’ve redesigned both boards. The base plate now has only two single pin headers. This is instead of the two transistor footprints. This provides a connection to create a ground copper pour. I have also shuffled the components around on the oscillator board to enable the micro switch to be placed on the far right, for unobstructed use. This required moving the key socket to the rear but also gives enough room to move the potentiometers, allowing room for the missing fixing nut.

CW Practice Oscillator v2.04 StAR Edition

CW Practice Oscillator v2.04 StAR Edition

Having now taken another stab at the design, I’ll get them fabricated and see if they are the final version!

As I was writing this entry, another board arrived; A 7 Decade Resistor Substitution Board. This is one of a few PCBs I have designed specifically for the students I help teach every week.

7 Decade Programmable Resistor Board v1.00

7 Decade Programmable Resistor Board v1.00

The idea is that the students get plenty of soldering practice and also end up with a useful item to take home and use in their own electronics experiments.

7 Decade Programmable Resistor PCB

7 Decade Programmable Resistor PCB

Another one of these simple PCBs is a 555 LED Flasher. This should redily be built in under an hour, even for a beginner.

Simple 555 LED Flasher and Panelised PCBs

Simple 555 LED Flasher and Panelised PCBs

Here seen operating along side the panelised PCB. All the boards in this post were fabricated by JLCPCB.com I recently discovered that not only do they supply 10x boards smaller than 100mm x 100mm for $2 (Plus Delivery)*, but if you can panelise the boards within 100mm x 100mm, including 10mm border for ‘V’ grooves, you end up with more boards for your buck. There is a function on the order screen for this avoinding having to do it manually.

*Make sure the one single PCB’s size bigger than 20mm x 20mm otherwise a surchage is added.

Note: 555 LED Flasher and 7 Decade Programmable Resistor Substitution Board design files are now available on Non-AVR Projects Page.

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Oscillator Update

I successfully completed the Twin ‘T’ Oscillator, original by Mike Maynard – K4ICY. It’s a great circuit and sounds really good. Much better than a raspy 555 version. Mike has been kind enough to put a link to my project on his website.

I showed my friend Phil G3MGQ who liked the design but suggested a couple of improvements to make it a good project for UK Foundation/Intermediate radio licence students. Phil requested the addition of an LED to facilitate sending Morse Code across a classroom and a microswitch to act as a minature Morse key on board. I have since added these features. I also had a think about how the board was to be used.

CW Practice Oscillator v2.02

CW Practice Oscillator v2.02

Because the boards may be left unboxed, I reasoned that a better placement of the controls and sockets would make for easier operation. I moved the pitch and volume controls over to the left of the board and the sockets to the right. I also added an on board switch on the power input. The microswitch Morse key is in the middle of the board on the front and the LED on the rear of the board with it’s contacts orientated across to facilitate bending over to the vertical. It can also accomodate right-angled LEDs too.

Because the board is intended to be used bare or cased, I also designed a base panel to add so that the contacts underneath are prevented from shorting on any surface it is used on. It’s a blank PCB but KiCad seems not to want to do a copper pour unless there are at least some connections in the design. I put a couple of transistor footprints on the board for this reason. They serve no purpose except to allow the copper pour.

CW Practice Oscillator v2.02 Base Panel

CW Practice Oscillator v2.02 Base Panel

This panel can be added to the oscillator board with standard M3 bolts, with a single nut to separate them. Then four rubber stick on feet can be attached to prevent movement.

This updated design with be added to the Non-AVR Project page once built and proved.

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Radio Network

I’ve been a licenced radio amateur since 1993. My callsign is G0TDJ. Morse was always my first love in radio although I have tried many other modes. Recently, ‘Network Radio’ was drawn to my attention by an article in a UK magazine called Practical Wireless by my friend Tim Kirby G4VXE. In the article, Tim explained the basic concept of network radio and mentioned devices that you could use. Included with these were smartphones paired with an app called Zello. I loaded up the app on my iPhone and discovered that I already had a contact. Another of my friends, Ian G7PHD. Then I remembered that Ian and I had tried out Zello a few years back and found it laclustre in performance.

It appears that Zello has now grown up as an app and works very well. At around the same time, within part of my research, I came across the ‘Network Radios‘ Facebook page. Originally, this was a single channel on Zello created by Karl G1YPQ, but has now grown to several other channels, plus a few in reserve.

It didn’t take me long to want to do some CW (Morse) on a zello channel but the devices that Zello runs on, be they smartphones or dedicated, don’t give provision for CW in any way. I sought to fix this deficiency. To this end, I designed an adaptor for my Inrico TM-7 to enable other audio sources to be fed into the microphone input. This uses the popular computer networking connector, the RJ45.

TM-7 Audio Switch v1.01

TM-7 Audio Switch v1.01

The standard microphone is fed into socket J1 and a straight through network cable is used to connect J2 to the TM-7 microphone socket. The radio can then be switched between the standard microphone or an external audio source fed into the jack socket on the back of the pcb. There is a further jack socket to provide facility for a footswitch. The pcb illustrated is the second version of the board with added screening connections on the RJ45 sockets and a breakout header for the signals. This board is currently being fabricated.

Meanwhile, I needed a method to get some Morse tones into the radio. I found a nice Twin ‘T’ oscillator on Michael Maynard K4ICY’s website. I wanted to make an oscillator that could be used for practice, as well as an audio source, so I modified Michael’s design slightly by changing the transistor amplifier to an LM386. I have published the details for this on the Non-AVR Projects page.

There is a current issue with the use of the first version of the audio switch and the oscillator. The signal is very noisy. I believe it is because the devices aren’t screened. Further testing will be done when the new boards arrive.

Another, more traditional radio, project I have been working on is a Morse Code Decoder. Although I am reasonably profficient in Morse and have many ‘normal’ contacts, I find it difficult, at least time consuming, to read callsigns in contests. The idea I had was to build a Morse decoder to catch the very fast callsigns and enable me to give more points away! I came a cross many designs online, but the one I chose to replicate I found on Hjalmar OZ1JHM‘s website. It is an ATMEGA326 with a potential divider and LED. Hjalmar provides the circuit in Fritzing style and conventional schematic and the code to drive it. I designed a PCB and modified the code to use a 2×24 line LCD display.

CW Decoder v1.01

CW Decoder v1.01

I had a few issues with the first PCB I had fabricated. For some reason, I had put the LCD pins in the wrong place for a straight through ribbon connector. I obviously didn’t check the design enough before I sent it. Coupled with this, on the first PCB I built, there was a problem with the clock oscillator. I attempted to fix this but the tracks on the PCB started to lift. I cut my losses and built a new one. This one, as you can see in the image above, worked fine. The newer version of the board, yet to be fabricated, includes the display pins wired correctly.

 

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You’re just Multi-faced

A lot has been going on lately so I thought I’d update the blog with some of it. Starting with a small announcement. I secured the domain www.ProjectSPECCY.com It currently re-directs here. I am unsure as yet whether I will have a separate site or combine ProjectAVR and ProjectSPECCY here. Stay tuned.

On to the Multiface 128 recreation project. I have been attempting to find a source for an AT&Y SPEC-MATE which is a lesser known snapshot interface for the earlier Sinclair Spectrums. I used to use one back in the Spectrum’s heyday for hacking. Try as I might, I can’t find one for sale. I do know somone who has kindly sent me images of the device, including some good internal shots. This has proved difficult to copy however.

AT&Y SPEC-MATE

AT&Y SPEC-MATE

Whilst I continue my quest to find a SPEC-MATE of my own, I thought I’d investigate other snapshot interfaces. I have prototyped the Spanish Phoenix III (Phoenix IV) and added 8K of RAM to it in it’s second iteration, making it a Phoenix V for me. Both these devices appear to run the original Phoenix ROM and also the SPEC-MATE ROM but neither will return to the program called when the NMI button was pressed. I’m still investigating. The problem may be that I am working from someone elses tracing of the Phoenix III circuit. I can’t be sure it’s accurate.

Still wishing to investigate these interfaces, I chose to work with the Romantic Robot Multiface 128. The Multifaces were probably the highest profile snapshot devices around for the Spectrum (and Amstrad & Atari ST). At the time, they were always a bit too expensive for me. Now as an adult, I have managed to collect three different models, one each of Multiface 1, 128 and 3. I also purchased a MultiPrint which is a similar interface but based around printing rather than snapshots.

Tracing the Multiface 128 circuit was quite a long drawn out procedure. First physically following each connection and matching them to a circuit I drew in KiCad and then designing a PCB. However, I did so and the results are a working recreation of the device. Details and Gerber files are available on the Non-AVR Projects page. Anyone can download the gerbers and use their favorite fabricator to manufacture a PCB and build their own. I am not distributing the ROM image since it’s copyright status is unknown, however a quick search for ‘Multiface 128 ROM version 87.12’ should turn up a useful image. This will need to be programmed into a 2764 EPROM for use on the interface.

Recreated Multiface 128 in situ.

Recreated Multiface 128 in situ.

I am pleased to say that with the UK school term well and truly re-started, I have again been asked to help teach some of the students at St. Richards Catholic College I help a fellow Radio Amateur, Phil G3MGQ, teach radio at the Foundation level. The college was one of the few chosen to contact Tim Peake when he was aboard the International Space Station and some of the students at the college have been inspired to obtain their radio licences as a direct result.

I was extremely lucky in bagging one of the new vDriveZXs (review) from the first batch sold. I have a ZX Interface One and two Microdrives but the drives are faulty. I was looking into repairing the drives but now, one of them at least, will become a vDrive. I will retain the internals though, for study and spares. The vDrive is a module that fits inside an original Microdrive case and emulates the original using an SD Card. This enables up to eight virtual drives to be seen by the Interface One and, of course, since the SD Card has a much higher capacity, you can have multiple sets of virtual drives available. I am looking forward to receiving my unit and fitting it in one of my old drive cases. QDos to Charles Ingley, the creator.

Just to whet your appitite, I have a few other things up and coming in the Spectrum arena but at this time, I can’t say anything. Full details will be published here in due course.

 

 

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Refurbishing a 48K Rubber Keyed Sinclair ZX Spectrum – Pt.6 Reassembly

It was finally time to reassemble the machine. I had one last cursory check of both sides of the board, just to make sure it hadn’t picked anything up that may cause an issue and placed the board in the lower case tray. I fixed it in with it’s single screw near the center.

ZX Spectrum PCB Back in the case lower half

ZX Spectrum PCB Back in the case lower half

One more check to see that the Upper RAM module was OK and then to plug the keyboard ribbons in. Typically, the keyboard ribbons are quite delicate so a lighter touch is required but in this case, the after-market membrane had slightly more substantial ribbons. I still took my time and made sure not to put too much pressure on them. Once the ribbons were in place, I placed the halves of the case together and inverted the machine to screw in the brand new set of screws I got from Retroleum.

New Screws In Place

New Screws In Place

It is important not to overtighten the screws, especially on an old case. When you are getting to the point where the screw is tightening, slow down and just tighten it enough to hold the case securely shut. Old plastic, especially if it has been left for years in a loft, will go brittle and it is really easy to break the screw colums or to strip the threads.

Also, from Retroleum, I purchased a brand new set of feet to really finish the job off.

Fitting New Feet

Fitting New Feet

At last, a fully refurbished 48K Rubber Keyed Sinclair ZX Spectrum!

Fully Refurbished 48K Rubber Keyed Sinclair ZX Spectrum

Fully Refurbished 48K Rubber Keyed Sinclair ZX Spectrum

The last step in this long process was to give the machine a test with one of my favourite games. I plugged in the ZX-HD and divMMC Future interfaces and fired up the Dell monitor. I loaded Batty and played a few rounds, all was well.

Testing the Refurbished Machine

Testing the Refurbished Machine

I hope this series has been helpful and enables collectors of older ZX Spectrums to maintain them in working order. Help in reparing these machines can be sought in two great Facebook groups, Spectrum4Ever and Spectrum For Everyone.

Series Index: Refurbishing a 48K Rubber Keyed Sinclair ZX Spectrum

 

 

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Refurbishing a 48K Rubber Keyed Sinclair ZX Spectrum – Pt.5 Case Cosmetics

Now the Spectrum’s board was fully refurbed and tested working, it was time to turn my attention to the case, keyboard and fascia. The original fascia looked a little tired and was dented so I had ordered a replacement from ZXRenew It arrived well packed and in good time.

I found it quite easy to remove the old fascia which gave me access to the keyboard mat and membrane. The membrane looked as if it had already been replaced at some point and was still fully working. I put that aside for reseating later on.

Case and Keyboard Mat Cleaned

Case and Keyboard Mat Cleaned

It was then down to washing the keyboard mat and case, carefully in mild soapy water and rinsing off. I took my time, trying to rid the keyboard mat of accumulated dirt. The bottom of the case was quite easy but, on the top half, I found the glue that held the old fascia on to be a real problem. I tried various substances but in the end, I pretty much used my nails and fingers to rub it off. Not a pleasent job. Perhaps I should have waited until I had a suitable substance available but I was keen to finish the refurb.

After drying it all off, the next step was to re-ink the ‘ZX Spectrum’ text in white. I had managed to get the remnants of the old ink off and I now used a Extra Fine Tip White Ink Pen from Mutant Caterpillar to carefully re-ink the letters. It was no easy job. Because the letters had been worn over the years, the edges were not very defined. It took me several attempts. I am happy with the outcome, although I need a lot of practice if I’m to get results like @ZX_Priestess seems to manage!

Once I was sure the ink had dried, I replaced the membrane, keyboard mat and prepared to fix the new fascia on.

Keyboard Membrane Back In Place

Keyboard Membrane Back In Place

ZX Renew had kindly included some 3M branded fixing strips to use with the fascia. I applied these one at time and cut a shorter length to fill the gap on the front.

Fixing Strips Applied

Fixing Strips Applied

Getting the backing off of the strips proved to be challenging. Patience required! Once I had all the strips in place, I checked over the new fascia and prepared it to be fixed. I then removed the other side of backing from the fixing strips.

Ready to Fix On the New Fascia

Ready to Fix On the New Fascia

To avoid marks on the new fascia, I used a pair of cotten gloves I have lying around. The fascia fitted perfectly and I went around the edges checking it had made contact with the fixing strips. The left and right sides required a little extra persuasion.

New Fascia in Place

New Fascia in Place

I then moved straight on to the next step, the final assembly.

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Refurbishing a 48K Rubber Keyed Sinclair ZX Spectrum – Pt.4 Custom Composite Video Mod

Now I had the Spectrum PCB fully working, I wanted to add a Composite Video modification to round off all the refurbishments. I had already used a neat circuit advised by Andrew Gostling when I repaired a previous machine.

Inverted Emitter Follower Composite Mod

Inverted Emitter Follower Composite Mod

Although that mod works fine, I wasn’t happy with the components being self-suspending. So I set about designing a PCB to house Andrew’s version of the mod, the more usual transistor mod and the simple capacitor mod.

Spectrum 48K Composite Video Mod PCB

Spectrum 48K Composite Video Mod PCB

The above image is the result. This PCB is made the same size as the one inside the modulator so it can replace the original completely. This is quite involved but I believe it to be very worthwhile. Now I have built one up and found Andrew’s mod to work just as it did self-suspending, I have published the design files for the board on a separate page. I did have a conversation with Andrew around the preservation of the original modulator PCBs. Andrew advocated a mod to be done retaining the circuit board inside the modulator, however, I see no issue with removing the internal PCB, so long as it is kept in a state with which it could be re-installed at any time. As long as the original PCB is removed carefully and without undue force, it can be put into storage for such an eventuality. I will leave it to the reader to decide which option suits them.

The first step in fitting this new board into the modulator is to carefully extract the modulator from the Spectrum’s PCB. First I de-soldered both the 5V input and Video Input leads from the Spectrum’s PCB.

Disconnected Video and +5V Leads

Disconnected Video and +5V Leads

Then it was onto the back to de-solder the large tags on either side of the modulator. These can be a little stubborn and, being heatsinked to the body of the modulator, they do drain the soldering iorn’s heat quickly. A good wattage iron and persistence is the key. When I finally freed the modulator, it came away quite easily and I cleaned the holes left on the board in preparation to replace the modulator box later on. Next, carefully solder in your choice of components to the new pcb. You need only choose one option. In this instance I used Option 1 which is Andrew’s Inverted Emitter Follower design.

Modulator Removed and New Board Soldered Up

Modulator Removed and New Board Soldered Up

Next I needed to remove the old pcb from the modulator. This is held in by several solder spots and the two leads coming in through the side of the case. First I de-soldered the solder spots underneath. this requires a freshly cleaned out de-solder pump. With patience, you can get the desolder pump in place and bring the soldering iron carefully in to melt the solder and trigger the de-soldering pump. I took me a few tries but because there is a defined gap between the PCB and the modulator case, it creates a definite separation when the PCB finally becomes free of the box.

De-Soldering the Modulator's PCB

De-Soldering the Modulator’s PCB

You may find that the screen that goes down the center of the PCB is also soldered to the inside of the Modulator. In this case, just de-solder as you have been doing. This particular one was only secured on the PCB but the previous scrap one I had practiced on was soldered on both sides to the inside of the modulator box. Once I had de-soldered the points underneath, I de-soldered the 5V line and the PCB came out with a bit of gentle persuasion. I boxed the old PCB up in a box, labeled it and placed it into my ‘stock’.

Modulator's PCB Removed

Modulator’s PCB Removed

Next on the agenda was to fit the new PCB. I used Blu-Tack once more, to support the board whilst I got it going. I removed it as soon as two opposing points were soldered.

If I had known how difficult hooking up the video socket to the PCB was going to be, I’d have done that first. If you are carrying this mod out, I’d urge you to save yourself 20 minutes of frustration by connecting the video output point on the PCB to the Spectrum’s output socket before you begin to solder the board into place!

I recycled one of the old wires for the video feed and used a new insulated lead for the +5V. Simply maintain enough length for fitting into the Spectrum PCB once the Modulator box is refitted if you are doing this yourself.

New PCB In Place and Connecting Leads Attached.

New PCB In Place and Connecting Leads Attached.

I could now refit the Modulator box to the Spectrum’s PCB. This was pretty straightforward having prepared the tag holes earlier. Once the box was in place, I soldered the flying leads in place too.

Modulator Box In Place and Connections Made

Modulator Box In Place and Connections Made

Now I’d got the Modulator box back in place with all the connections made (The ground being connected via the Modulator case), it was time to test the Composite Output. Unfortunately, as regular readers will know, I haven’t got a large Composite Monitor. However, I have got one of the small 7in models meant for installing in cars. This makes a reasonable test monitor, although would be a little difficult to use for any length of time.

Composite Video Test

Composite Video Test

The image above, shot on my iPhone, shows the board with Composite Output working on the bench. After testing this, I gently pulled the slack cable on the +5V lead into the Modulator box and replaced the Modulator’s cap.

Next, I turned my attention to the cosmetics of the Spectrum’s Case.

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