[IC] PRIZMA - 2 channel, 16 step sequencer with rainbow

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Mugsy1999
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Post by Mugsy1999 » Mon Jul 23, 2018 2:02 am

Following up on my Prizma+ build as I've got it working now.

I had a lot of trouble with this module. It was probably the most difficult I had attempted if only for the size of IC1 and the number of small pads on the LEDs where the chip legs don't extend past the LED ( what is the name of that chip style i dunno ). It started with the LEDs, I had to replace 4 or 5 of them. Not sure if it was bad chips, or my soldering was damaging the very fine internals of those things. Finally I got 16 working LEDs.

When I got it all built and ready to test, to my dismay I got bad voltages at both the outputs. Reading through the calibration instructions, it seemed to me that I should be seeing 0V for each calibration octave, and then I'd adjust them down, ( which is a misread ) but my voltages were a constant 0.185V. Testing the output as I moved between octaves I was seeing no change. After lots of measuring voltages and continuity testing I determined that it could only be a problem with the IC1 DAC chip. The Opamps following it were fine and the Teensy was probably ok, though I didn't have an oscilloscope to test the output to the DAC.

So, I re-ordered a DAC, removed that chip and put the new one in. Phew. Turned it on and - sadness - the same output. I can write code though, so I wrote a simple program to make the DAC output ever increasing notes on the red output. That worked! So now I was very confused, and back to being suspicious of the DAC calibration. Careful reading of the calibration text says that you should tune each octave to it's own voltage - 0v, 1v, 2v, etc. but my outputs are are all at a constant 0.185V! I painstakingly turned them down to 0v, up to 1v and running sample sequences in chroma mode made at least some different notes. But the prospect of the number of turns it would take to get up to 7V made me think the process was crazy.

Well I guess it was, and the default state is not supposed to put you in a constant 0.185V on all octaves, it's supposed to get you close to each of the target voltages. I heard back from Szabó ( from Doboz ) on the Doboz Builder's Aid facebook group and he gave me a secret combo to reset the calibration ( it's something like hold the lower encoder and press upper? I never quite nailed it down and it's finicky. holding lower without upper exits calibration, so you have to hold upper soon after depressing lower. )

That worked for red channel. I suppose in all my debugging, I had loosened the thonk jack for blue channel cv, so I was still getting nonsense values there, but intermittently the correct notes. Reflowing all solder pads on the thonk jacks solved that.

My suggestion if anyone from Doboz reads this is to clarify the calibration text a little bit to make clear what values you should expect, and including the shortcut to reset the calibration in the case where the default calibration does not initialize properly. I take blame for misreading, but the text could be clearer.

Hopefully this is helpful to someone else building a Prizma+. I didn't find a whole lot of discussion on issues with the module and I'm happy to share any advice I learned along the way.

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auxren
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Post by auxren » Mon Jul 23, 2018 4:17 am

I built one and it worked right away with no problem using the supplied DOBOZ instructions. :nana:

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av500
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Post by av500 » Sun Jul 29, 2018 11:43 am

it seems that you need to perform the calibration procure after flashing the firmware in order to get the DAC to output correct voltages

that was suggested by Doboz.audio and fixed the prizma+ for my friend

elodin
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Post by elodin » Fri Aug 24, 2018 10:29 am

Are pcbs and panels available anymore?

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khyber
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Post by khyber » Tue Nov 13, 2018 10:09 am

I might have a panel/PCB set available for sale if anyone wants to purchase one. Not sure if I will get around to building this project anytime soon

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muted
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Post by muted » Sun Jan 20, 2019 1:52 pm

I have an issue that seems to be relatively common: Most times i start my Eurorack system, the Prizma is just giving me all blue (and powerful) LEDs, however once in a while it starts up and functions.

I have the Pusherman version of the board, so... not the latest one I suppose.

Is there an official fix for this issue? I have seen some say that they mod the board to accept the 5V line from the busboard, but it would be nice with an official guide or something before I mess everything up.

Update: I removed the voltage limiter and hooked up 5V directly to the limiters old output from the busboard. I now have a higher succesrate for switching it on, but its still only every 4th time or the like.

lasoie
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Post by lasoie » Tue Jan 29, 2019 10:53 am

muted wrote:I have an issue that seems to be relatively common: Most times i start my Eurorack system, the Prizma is just giving me all blue (and powerful) LEDs, however once in a while it starts up and functions.

I have the Pusherman version of the board, so... not the latest one I suppose.

Is there an official fix for this issue? I have seen some say that they mod the board to accept the 5V line from the busboard, but it would be nice with an official guide or something before I mess everything up.

Update: I removed the voltage limiter and hooked up 5V directly to the limiters old output from the busboard. I now have a higher succesrate for switching it on, but its still only every 4th time or the like.
I've got the same problem here. Each time I reboot my system, the firmware looks like it has gone from the chip. Tried it with different chips with same result…
Anyone has a clue on this ? i'd really like to have a working module…

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dooj88
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Re: [IC] PRIZMA - 2 channel, 16 step sequencer with rainbow

Post by dooj88 » Sat Jan 18, 2020 1:22 pm

nevermind, brain fart. still loving mine of course.

snowtires
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Re: [IC] PRIZMA - 2 channel, 16 step sequencer with rainbow

Post by snowtires » Wed Jul 22, 2020 9:00 pm

Is there a working link to calibration instructions for Prizma v3? I just finished building one and can't find anything.

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robduarte
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Re:

Post by robduarte » Wed Sep 16, 2020 7:01 am

lasoie wrote:
Tue Jan 29, 2019 10:53 am
muted wrote:I have an issue that seems to be relatively common: Most times i start my Eurorack system, the Prizma is just giving me all blue (and powerful) LEDs, however once in a while it starts up and functions.

I have the Pusherman version of the board, so... not the latest one I suppose.

Is there an official fix for this issue? I have seen some say that they mod the board to accept the 5V line from the busboard, but it would be nice with an official guide or something before I mess everything up.

Update: I removed the voltage limiter and hooked up 5V directly to the limiters old output from the busboard. I now have a higher succesrate for switching it on, but its still only every 4th time or the like.
I've got the same problem here. Each time I reboot my system, the firmware looks like it has gone from the chip. Tried it with different chips with same result…
Anyone has a clue on this ? i'd really like to have a working module…
Same here. It's definitely software related. I can program the atmega with anything else (like the neopixel test programs from adafruit) and it works fine. I 'm hoping they will just open-source the firmware for this old version so I can fix it. Otherwise, I have ideas for several alternative firmwares - just not the time right now to make them happen! I'm emailing doboz again right now to beg them to open source the code.

Rob

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