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Tony Deff
Joined: May 25, 2008 Posts: 51 Location: Suffolk, UK
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Posted: Sun Mar 22, 2009 11:21 am Post subject:
Programmable Logic as Equal-Temperament generator Subject description: Suitable Devices (if any) |
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Since the demise of 16-pin Top-Octave Generators (TOGs) [or Top-Octave Synthesizer (TOS) in the USA — as though it were inferior to a real top-octave], many people have been nostalgically looking to re-create these within programmable logic or micro-controllers, and such wishful thinking can out-weigh real appreciation of the limitation of these devices.
Inevitably, the PIC series has been the subject of such debate, and intrigued by a claim that can be found on the web, I took a look at how an entire top-octave could possibly be output from the humble PIC. (See the thread in the Developer's Corner from last year).
When it comes to programmable logic, the Amateur faces the problems of acquiring suitable devices and the mountainous obstacle of programming the damn things. Programming algorithms are usually protected by the Official Secrets Act, and we can all guess the reasons behind (preventing the runaway success of a device by hoards of amateurs buying it, and somehow upsetting the market?)
Nobody wants to be abducted in the middle of the night through Extraordinary Rendition for having cracked the 22V10 algorithm.
But we need far greater resources than the 10 miserly flops of a 22V10. Twelve divisor outputs of 10 or 11-bit counters require some 120+ flops.
What devices are available to the amateur, have solderable pins, can be programmed by a home-built, or affordable, programmer and have more resources?
A medium-size programmable-array may suffice if they could be used in parallel. For example, suppose we could implement a 1-of-12 divider via a binary select code, so that a multiplexed system used just as many note-selectors as required, or if a similar single-note generator could be cascaded so that each generator produced the next semitone, and the whole set could be transposed?
Many years ago, when bored at work, I wrote a PALSAM code that generated 1-of-16 semitones using a 22V10. It was written especially considering the device's limitations (which involves unorthodox approach, minimization and pin-juggling), but I did it. (At least theoretically: it compiled without error, but I was never able to burn a device and try it). |
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JovianPyx
Joined: Nov 20, 2007 Posts: 1988 Location: West Red Spot, Jupiter
Audio files: 224
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Posted: Sun Mar 22, 2009 12:35 pm Post subject:
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Someone on Synth-DIY (email list) is making a TOG using a PIC. Not sure which model, but he's making them available. I think it is Tom Wiltshire, but I'm not sure. You can sub to the list if you're not already subbed and just ask the question there. Getting one of his units takes all the nasty programming bother out of it, assuming they are not all spoken for.
I hope this helps. _________________ FPGA, dsPIC and Fatman Synth Stuff
Time flies like a banana. Fruit flies when you're having fun. BTW, Do these genes make my ass look fat? corruptio optimi pessima
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yerpa58
Joined: Mar 08, 2008 Posts: 57 Location: Wisconsin
Audio files: 4
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Posted: Tue Mar 24, 2009 9:22 am Post subject:
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This subject has come up before:
http://electro-music.com/forum/post-188525.html
I can program PIC 16C54 chips from OldCrow's "oct54all.asm" code if anybody is interested, but there are also plenty of cheap PIC programmers out there. |
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skrasms
Joined: Feb 21, 2008 Posts: 121 Location: Portland, OR
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Posted: Tue Apr 07, 2009 5:49 pm Post subject:
Re: Programmable Logic as Equal-Temperament generator Subject description: Suitable Devices (if any) |
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Tone-Deaf wrote: |
What devices are available to the amateur, have solderable pins, can be programmed by a home-built, or affordable, programmer and have more resources?
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Altera has some really nice CPLDs in the one to two dollar range (through digikey) with 32 and 64 macrocells. I don't recall what that works out to in terms of actual usable gates, but it's a lot nicer than a 22V10. The only catch is that you have to buy PLCC adapters to give them solderable pins. It adds about $1 per chip.
Altera's programmer is prohibitively expensive, but Terasic and others make knockoff programmers for $150 and under. The software is free.
Look up the MAX3000 series if you're interested. _________________ Software and Hardware Design |
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slabman
Joined: Sep 01, 2005 Posts: 102 Location: UK
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Posted: Fri Apr 17, 2009 7:42 am Post subject:
Silicon Labs Si5334 |
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I just came across this - it could be a contender: https://www.silabs.com/products/clocksoscillators/anyrategeneratorsandbuffers/Pages/default.aspx
Quote:
The Si5334/38 any-rate, any-output quad clock generators are high performance, low jitter clock generators capable of synthesizing any frequency on each of the device’s four differential outputs. ... Each output clock can be individually programmed to generate any frequency from 0.16 to 350 MHz and select frequencies to 710 MHz at very low jitter (1 ps rms typical random jitter) and zero ppm frequency error.
End quote.
3 of those gives you an octave |
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urbanscallywag
Joined: Nov 30, 2007 Posts: 317 Location: sometimes
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Posted: Fri Apr 17, 2009 11:07 pm Post subject:
Re: Programmable Logic as Equal-Temperament generator Subject description: Suitable Devices (if any) |
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skrasms wrote: | Tone-Deaf wrote: |
What devices are available to the amateur, have solderable pins, can be programmed by a home-built, or affordable, programmer and have more resources?
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Altera has some really nice CPLDs in the one to two dollar range (through digikey) with 32 and 64 macrocells. I don't recall what that works out to in terms of actual usable gates, but it's a lot nicer than a 22V10. The only catch is that you have to buy PLCC adapters to give them solderable pins. It adds about $1 per chip.
Altera's programmer is prohibitively expensive, but Terasic and others make knockoff programmers for $150 and under. The software is free.
Look up the MAX3000 series if you're interested. |
Gates don't really matter in this case, its number of flip flops (which is equal to the number of Marocells).
If you're going Altera the smallest MAX II CPLD has 240 LEs, easily enough for a TOG. Cost is ~$6 in quantity 1, but it does have an on board oscillator that I think would work in this application.
There are knockoff programmers on eBay in the $30 range. A friend has the tiny one that looks like a thumb drive, it works well so far. |
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Gordon2
Joined: Apr 13, 2017 Posts: 2 Location: Ulm, Germany
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Posted: Thu Apr 13, 2017 8:06 am Post subject:
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It's quite easy to use a very cheap chinese altera CPLD board (eg EPM1270t144) to make a top octave generator. In fact you can get most of the lower octaves as well from one board, even all free phase if you want. The biggest difficulty is getting your head around the (free) 2GB Quartus II software for programming. I use schematic entry as opposed to Verilog or VHDL entry.
You don't even need to use optimised divider ratios as the clock frequency is so high - 48MHz - that practically any ratios are accurate enough (ie accuracy better than 1 cent). The main limitation is the number of I/P and O/P pins. Would be great if a midi decoder could be included in the design - a bit beyond me!
Gordon Nudd |
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