EPROM Xplorer

[PHOBoS]

Last year a huge box full of EPROMS arrived at the moon base. I didn't have a way to program them so I first made a programmer using an arduino to
solve that problem. It's a bit more complicated than using EEPROMS because you need a couple of different voltages but with the help of a couple of
LM317 variable regulators and some extra logic I got that working. So now what to do with them ?

One of the things they are very suitable for is storing sequences so with that in mind I got thinking about what kind of sequences and a circuit to make
use of them. At the very least it needs a counter to control the address lines and the 8 data lines could then be used as gate outouts. I also happen
to have some very nice 8-bit parallel input CMOS DACs to use the data outputs as a CV source. After some calculations I figured out that it is pretty
easy to make a V/Oct output which can be set to semitones by using only 6 bits.

Initially I thought about using discrete logic but with the features I wanted to add that started to get quite complex so I'll be using an arduino instead.
One of the things I had quicky decided on is that I wanted some 7-segment LED displays for a bit of retro look to go with the EPROMS. I do have a lot
of displays (also arrived with the EPROMS) but I'd need 3x 5 digits so 15 displays with at least 7 segments (8 including the dot) each to connect and
that's already 105 connections to wire up, so unless I'd design a PCB for it that's quite a tedious job. Also the easiest way to drive them is with the
help of a special driver chip like the MAX7219 which would only require 3 lines of the arduino. The same could be achieved using shiftregsiters but
that requires 1 chip for each digit while an MAX7219 can drive 8 digits at once and it takes care of multiplexing internally (+ has brightness control).

Looking online I found the chips for about 1,50 but also complete modules incl 8 digits for 2,- so that seemed like a better options. It saves me a lot of
time not having to solder them all and the displays are also much smaller then the ones I have so it saves space aswell. I don't really need 8 digits
though but they come in handy for displaying some extra info. They are soldered a bit crooked but for what I paid I can live with that. On a side note
the ones I have came with a protection diode in series with the V+ line which is great but the V+ output (for linking more modules) is connected
after this diode, so if you link more of them the voltage gets lower for every added module. Easy solution is to remove the diode and link the pads
together at least for every module added after the first one.

so why 3 displays you might ask ?
I mentioned it needs a counter and the idea is to be able to set both the start and end position of this counter for which I'll be using rotary encoders.
Both need to be displayed to be able to see what they are set to which could be done in binary with LEDs but using 7-segment displays makes it a
bit more practical in use. The 3rd display is for showing the current address (position of the counter). Note that I'm designing it for 256/512K EPROMS
the latter having 16 address lines so requires a 16 bit counter to count through every address, hence 5 digits (max value is 65535). Besides the LED
displays I am also using some vintage 5 mm red LEDs for displaying the 8 data outputs.

After doing some tests I found out that having a start + range (number of steps) setting is more practical than a start + end setting which brings me to
the reason for calling it an Xplorer. I could deliberately create gate sequences and since it has a CV output also musical scales which I will probably do
but it is more appealing to me to put all kinds of data in the EPROMS without thinking about how it will sound. This data can come from anywhere for
example I might convert some images or just use a semi-random generator or mathematical function. And then the fun begins of exploring what kind
of music is hidden inside. For me this is a great way to get some inspiration to use as a starting point. Also because I can set the start position to any
point I could still get some suprises if I would deliberately choose certain patterns (I can also scroll from one into another). I think pretty much all the
EPROMS I have are empty btw so I don't have any unknown data to explore.

some other features:
as mentioned I can choose between start+end or start+range
it has a normal/alternate (up<>down)/random option
direction can be inverted with a toggle switch and the counter can be halted if that switch is in the center position
an internal oscillator and external CLK input to set the tempo.
a reset button to restart the counter
a midi output which can output the same notes as the CV output but I could program different functions.
a connection for my serial patchbay which has 32 inputs and 32 outputs with 6.3mm jack connectors (could be used to add some extra controls).
Of course it is also useful without an EPROM as another arduino based controller.

If I can run it fast enough it could be used to create audio waveforms directly (as grumble is doing here) but I haven't tested that yet.
I also posted this photo there of the xplorer in progress:



I am currently working on the hardware and will post a bit more about that later.

[PHOBoS]

btw, an earlier xploration resulted in Reconstruction Of Matter.
You can't hear much of it in the actual track but it did work as intended

[PHOBoS]

One thing I don't like about the display modules is that the displays aren't centered on the PCB and as a result not centered between
the mounting holes. So I made an aluminium bracket to take care of that which also helps to make it a bit sturdier.

For the frontpanel I am using a piece of copper clad board which had been collecting dust for 20 years or so. I did consider etching it
and use the copper side for the labeling but that can be a bit difficult to read (without a backlight) and I might screw up the process.
So I am just doing the usual and will add a paper front to it. The copper does add a nice groundplane to it though.

The panel has been drilled and cut and I also soldered the circuit on a piece of perfboard. Now I need to do some wiring and then
I'll have to make a case for it. I am not entirely sure yet if I have enough crimp connectors but I think I'll just make it. I also don't
know if I have the correct pot for the internal oscillator and I certainly don't have the knobs I want for the encoders but that is of
less importance.

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[Grumble]

Nice PHOBos!

How do you plan to generate the clock frequency? You know I'm a big fan of the AD9833 from Analog devices, (just 4.21€ @ Alieexpress)

[PHOBoS]

Just a standard inverter based oscillator which could go into the MHz range but Iĺl keep it much slower. I might do some test to see how fast I can run it
with the current code but as a start I could just disable the CLK and let it run free to see what it gets up to. Wavegeneration isn't really the purpose of
this circuit anyway but it would be a nice bonus.

Interesting chip that AD9833, could be useful for something else I want to try but I'd need a bunch of them which would get too expensive.

[blue hell]

Nicely weird project!

[PHOBoS]

Did some wiring and a quick test and it seems to work ok sofar. The 5V regulator is getting toasty but since I tested with a 12V
wallwart which I measured to be 14V once connected to the ciruit that's not really surprising. I will put a heatsink on it just in case
but I'll probably use it with a lower supply voltage anyway.

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[PHOBoS]

done a bit of woodworking, if you can even call it that.

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[PHOBoS]

I don't have the right knobs yet and the pot for the internal clock generator needs to be replaced, but this is how it looks now.

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[gabbagabi]

looks great!
well done,
as always!

[gabbagabi]

Segor is selling programmed eproms
https://www.segor.de/#Q=27C1001-120%252Fprogrammiert&M=1

[PHOBoS]

interesting, although it would be a bit silly for me to buy EPROMS with the amount I already have. Shipping costs also seem to be a bit high
and they are too large but they could still be used. However, that does make me think that I might be able to find some EPROM images for all
kinds of things online. I've only looked for musical applications in the past (like drums or waves) but anything that fits in a 256K/512K EPROM
could be used. Actually smaller of larger could be used as well just have to adjust them a bit. There should be archives with ROM images for
games available I think.

[gasboss775]

Hi Phobos, nice idea! 😀

Are your eproms blank or do they have random stuff on them?
If they do you could try random eproms and see what patterns or waves come out of them instead of specifically programming them.

[PHOBoS]

I am pretty sure the ones I have are all empty, at least I didn't notice any with stickers on them and the ones I tested were empty.
But yeah, exploring random data was the initial idea behind it