<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">I think the tonewheel "n/m" thing is actually quite a bit harder to do. The obvious way would be an NCO, since that gives you the fractional divider structure, the n/m, but then you have a problem with jitter, which is not something the gearwheels in the original generator have to deal with. With rotating gears, you can multiply a frequency *up* or *down* by whatever tooth-ratio you like, within reason. Since in that situation you might be after sinewaves instead of squares, perhaps some kind of pulse-density-modulated sine output would be ok. Yes, there'd be some small amount of jitter, but after the PDM is filtered, it might well be inaudible.<div class="">It's actually a situation where DSP with a fairly low sample rate is more than acceptable, since we're only producing sinewaves and the highest sine frequency in the Hammond organ isn't that high - just under 6KHz. Hence a fairly modest DSP running at even a 20KHz sample rate could generate the sines with no aliasing.<br class=""><div class=""><br class=""></div><div class="">The classic divide-down TOG can be done without jitter since it's always a whole number of master clock pulses. With the original chips running at about 2MHz, there's enough time to calculate the outputs on a basic processor going somewhat faster (20MHz, 32MHz, whatever).</div><div class=""><br class=""></div><div class="">I completely agree that RPi2040 is massive overkill even for a 12-note TOG, let alone six. It's been done on an AVR, so there's really no need for such heavy firepower!</div><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 27 Dec 2024, at 14:06, Roman via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">Following that route - why not make TOG replacement which produses exact frequencies of tonewheels, or better yet, switchable frequencies of every historical or another weird scales?</div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">Frankly, using RP2040 for 6 tone TOG is not so impressive to make video about it. Microcontroller based TOG replacements are available for decades now.<span class="Apple-converted-space"> </span></div><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">Roman<span class="Apple-converted-space"> </span></div><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">---- Użytkownik Tom Wiltshire napisał ----</div><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">.</div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">><span class="Apple-converted-space"> </span></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">><span class="Apple-converted-space"> </span></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">> I agree that it does seem a bit crazy to replace some basic logic with a whole uP, but the arguments for doing it are pretty convincing. Doing twelve 9-bit dividers in hardware is going to be a lot of chips, whereas the uP is only one. That makes it much easier to fit inside whatever it is you're fixing. And it's cheaper - a boardful of simple logic costs *more* than a processor these days because of the economies of scale. It *is* crazy to use a million transistors when 10,000 would do, but when they all come on one chip and costs pennies, it starts to make a lot of sense.</div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">><span class="Apple-converted-space"> </span></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">><span class="Apple-converted-space"> </span></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">> It terms of the technological limitations, all of the uP-based divider solutions I've seen are pretty much exact clones and just as limited as the original chips! They certainly keep the original division ratios and consequent frequency error.</div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">><span class="Apple-converted-space"> </span></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">><span class="Apple-converted-space"> </span></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin-top: 0px; margin-bottom: 0px;" class="">> There are a few original divider chips out there, but the people that have them want $30 a chip or worse for them. $1 processor wins over that every time.</div><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">________________________________________________________</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; 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