ChanServ changed the topic of ##yamahasynths to: Channel dedicated to questions and discussion of Yamaha FM Synthesizer internals and corresponding REing. Discussion of synthesis methods similar to the Yamaha line of chips, Sound Blasters + clones, PCM chips like RF5C68, and CD theory of operation are also on-topic. Channel logs: https://freenode.irclog.whitequark.org/~h~yamahasynths
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<andlabs>
update: knob tweaking an analogue synth is good stuff
<Xyz_39808>
expert knob twiddlers
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<andlabs>
that was the word I was looking for
<cr1901_modern>
I have a MIDI demo working on STM32. Might as well attach it to YM215- damnit, I don't have the DAC for it
<cr1901_modern>
well I can steal an FPGA one
<andlabs>
STM32?
<cr1901_modern>
ST Microelectronics microcontroller
<cr1901_modern>
They have a bunch of cheap dev kits with user USB on them
<Lord_Nightmare>
cr1901 cant you use one of those greenchip mini-cpld things as a ym2151 dac? iirc they are 5v tolerant
<Lord_Nightmare>
they have a built in dac too, but iirc its only 10 bits (I may be wrong)
<cr1901_modern>
Not enough state to hold the DAC
<Lord_Nightmare>
really?
<cr1901_modern>
Well, there's 16-bits
<cr1901_modern>
but I had trouble creating verilog small enough to emulate the exp2lin conversion
<cr1901_modern>
not to mention that indeed the built-in DAC is only 10 bits and 1v
<Lord_Nightmare>
sounds like you'd need two greenchips
<Lord_Nightmare>
one for L and one for R
<cr1901_modern>
greenpaks :P
<Lord_Nightmare>
er yeah
<Lord_Nightmare>
greenpaks
<Lord_Nightmare>
one for the L and R dacs... the log-lin thing could be an issue indeed
<Lord_Nightmare>
if it was a linear dac you could maybe fit something in to do dithering of the lowest dac bit to emulate a 16 bit dac?
<cr1901_modern>
ehh I could use a pass transistor for L and R and skip that emulation
<cr1901_modern>
IIRC the same circuit is used for L and R output
<Lord_Nightmare>
ah so sample+hold for l and r
<Lord_Nightmare>
using one dac
<Lord_Nightmare>
that would work
<Lord_Nightmare>
i'm curious if the ym3012 doesn't do that internally
<cr1901_modern>
ym3012, AIUI, uses a single exp2lin circuit
<cr1901_modern>
single shift reg
<cr1901_modern>
and it uses the L/R control signals to mux to two outputs
<Lord_Nightmare>
aha, so basically yes
<cr1901_modern>
clk, data, l, r
<Lord_Nightmare>
does it have internal analog filtering so the L and R outs don't look like a squarewave signal?
<Lord_Nightmare>
with opposite phase
<cr1901_modern>
I don't believe so, and not sure what you mean
<cr1901_modern>
from the patent the exp2lin phase is a bunch of pass transistors (but not an R2R dac- I don't remember the details)
<Lord_Nightmare>
oh
<Lord_Nightmare>
i mean, the log2lin thing isn't a dac, but how does it 'hold' the L or R pins at a voltage when they're not being driven (when the other channel is 'using' the log2lin circuit)
<cr1901_modern>
Hmmm, don't remember
<cr1901_modern>
On an FPGA I cheat and use sigma-delta of course