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PreenFM2 / PCB ready
« Last post by zelea2 on November 23, 2017, 11:44:02 PM »
I've added capacitors to all encoders and switches to eliminate contact debouncing in hardware rather than software. Also one pull-down resistor on pin D2 which is not currently used will be able to distinguish this board from stock (enable port D clock, input with pull-up D2, after 1ms read pin2: 1-stock 0-mine, disable port D clock).

The board is now finished and I've published the Gerbers and all the design files. I'll send it tomorrow to be manufactured and maybe I'll even get a black Friday deal.

I can now turn my attention to firmware until the boards arrive in 3 weeks time.
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PreenFM2 / Hiss
« Last post by feijai on November 23, 2017, 03:23:41 PM »
I have noticed quite pronounced hiss which occurs *only* when notes are playing, and is clamped thereafter.  Thus this seems unlikely to be the DAC, but is more likely something internal: perhaps the waveform resolution?  Some sounds have a more pronounced hiss than others; sometimes it's very loud, sometimes not, but it's always there.  Does anyone have a similar experience?  Any suggestions for dealing with it?
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PreenFM2 / Re: PreenFM2 SMD version
« Last post by norbim1 on November 23, 2017, 03:09:57 PM »
Hi,
My fork on STM32F4Discovery uses 48k sampling rate with overclocked firmware. It runs without problem, since the I2S DMA also spares some CPU load. See my fork on Github. Actually the F4Discovery uses CS43L22 dac chip, but the I2S code part could be reused for PCM5102 too.

http://ixox.fr/forum/index.php?topic=63425.msg64969#msg64969
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PreenFM2 / Re: PreenFM2 SMD version
« Last post by lokki on November 23, 2017, 09:00:18 AM »
since a lot of cpu will be saved by the extra controller that handles encoder etc. 44.1khz seems doable...
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PreenFM2 / Re: PreenFM2 SMD version
« Last post by Xavier on November 22, 2017, 09:00:02 PM »
Is there any reason you've chosen a non standard sampling rate? Instead of 42031.52 (1142 ticks) you could have gone for 44117.65 with 1088 systicks.
In any case 42KHz is just 5% away from 44.1KHz so I expect the internal PCM5102 PLL to lock.

It's only a performance reason.
With those sample rates, the CPU is close to 100% in worse case scenario (full polyphony with the most demanding FM algo, FX, arpeggiator..).
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PreenFM2 / Re: Latest firmware : 2.08a
« Last post by lokki on November 21, 2017, 08:51:14 AM »
yeah i could live with that :) with 8timbres, i have everything i could wish for...

so the question remains how and where one could implement that transpose/offset? i think the combo preset would be a better place then the sound preset, because one may want to use the same sound in different combos. otoh if it is easier to implement in the sound presets, than that is ok as well. might as well save two versions of the same sound with different offset/transpose settings. but i think xavier is hesitant to change the preset file structure, because it will "break" all existing patches. so it should be easier to do in the combo file..
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PreenFM2 / Re: Latest firmware : 2.08a
« Last post by chaocrator on November 21, 2017, 08:45:12 AM »
but more importantly now (with the 8timbres version) is actually the offset of midi notes to me. so that i can play treble parts and bass parts on the same controller. let's say i1 has a bass part and i2 has a melody part loaded. i can then play both on my controller but i cannot switch octaves on the controller so fast. if i could adjust an offset for i2 i would set it to +24 and all incoming midi on i2 would be 2 octaves higher.
as for me, the best option would be keeping transpose value for an instrument somewhere in the preset if necessary, but leaving MIDI channels settings independent of used presets/combos. (this is how my Novation Nova handles this stuff, and i love it.)
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PreenFM2 / Re: PreenFM2 SMD version
« Last post by zelea2 on November 21, 2017, 01:45:25 AM »
With solution1 mono cable will be possible but we'll need 2 PCM5102 even for 2 mono channels, right ?
So the difference is small, i don't have a strong opinion.

True, but I'm leaning more to second case because then you can stop one PCM5102, save some power and CPU cycles.
The PCM5102 shuts the audio channel down when it detects several consecutive samples of 0 on both channels.
I'll probably split the SoftMute signal to each PCM5102 to have extra control. The XSMT input also monitors the 5V supply
through the R35/R37 divider and shuts the audio down when the 5V supply drops. This will prevent pop noises at power-down or power loss.

I don't know the PCM5102 so i don't know what is best for it.

Sample rates are here :
https://github.com/Ixox/preenfm2/blob/master/src/synth/Common.h#L43
I have a firmware (with o suffix) which overclock the F4 to 192Mhz which allows a higher sample rate.

Thanks for all the clarifications.

The reason I'd rather not send I2S MCK clocks to PCM5102 is to reduce EMI (those clocks are 256*fs so 11MHz traces on the board).
If the PCM5102 doesn't detect a system clock then it switches to its internal PLL which samples the BCK frequency and generates internal clocks for its miniDSP.
It is not clear from the documentation how wide is the capture range of this PLL but it will definitely work for standard sampling frequencies like 32, 44.1, 48KHz etc.

The F4 has its own PLL for the I2S interfaces and those can be configured with very fine grain to almost any sample rate with less than 1% error.

With the PCM5102 we don't need interrupts to send the samples; each time a couple of new samples become available we test the DMA in progress bit and if it's not set we just configure a new DMA transfer over all available samples. Another way of doing this is to get a interrupt at the end of a DMA transfer and set a new one with the available samples.

Is there any reason you've chosen a non standard sampling rate? Instead of 42031.52 (1142 ticks) you could have gone for 44117.65 with 1088 systicks.
In any case 42KHz is just 5% away from 44.1KHz so I expect the internal PCM5102 PLL to lock.
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PreenFM2 / Re: Latest firmware : 2.08a
« Last post by lokki on November 20, 2017, 11:27:24 PM »
well, with the 8timbres version of the firmware that feature is not so pressing to me, since i can have 8channels in each preset.
but let's assume we are on the 4timbres version...
for live performances i have a controller that can send on 8 channels, since i never use them all on one preset (and since the channels represent different modes of the controller) it would be nice to switch the channels with the combo-presets. that way i can send a program change to the preenfm and all is adjusted for the next song/part whatever. reaching down to the preenfm and adjusting in the menu is of course no option :-)

but more importantly now (with the 8timbres version) is actually the offset of midi notes to me. so that i can play treble parts and bass parts on the same controller. let's say i1 has a bass part and i2 has a melody part loaded. i can then play both on my controller but i cannot switch octaves on the controller so fast. if i could adjust an offset for i2 i would set it to +24 and all incoming midi on i2 would be 2 octaves higher.

these two features (midi channel and offset) are very common on many multitimbral synths, and are usually part of the combo/multi preset, hence my suggestions. i'm simply used to that workflow and the preenfm would integrate much smoother into my setup... :-)

thanks for taking the time
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PreenFM2 / Re: Latest firmware : 2.08a
« Last post by Xavier on November 20, 2017, 11:08:43 PM »
what about pressing the inst button and pressing an encoder down, or inst and menu?

Maybe you said it, i don't remember.
But why do yout think it's a good idea to have the midi channel in the preset ?
Don't you have your synth/sound module with a dedicated midi channel each ?
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