Hi !
First of all, I let something in the code that you can delete :
between line 79 & 84
//I inverted pin 6 and 5 ... shame on me
if (n == 6) {
n = 5;
} else if (n == 5) {
n = 6;
}
Because I inverted my pins 5 & 6 so …
About your issue, you can replace the code line 77 by
int n = i - 2;
This should work fine!
It works! Thanks for the quick and concise reply! 
If CV_IN is coming off a jack that might be disconnected and you want to be able to read it as off if it is, then yes, you’d need a pulldown. 10k would work.
If you want to read an absent CV as on, you could use the internal pullup.
Thanks! 
I tested with 100K and seems to work with all the clock generator I have around.
Hi everyone.
Wanna inform everybody that I updated my code and schematics following all the valuable feedback I’ve got here : https://github.com/alexiszbik/arduinoarp_1.1
Thanks again ! 
Forgive my ignorance.
Why is there no switch in the schematic for the note B.
B is on pin D13, over on the upper left.
Doh!
I thought I was looking at an UNO.
Thank you.
Another project i need to revisit…
What is the reason for the protection using the two diodes? Is it to protect against reverse polarity from the clock signal?
Overvoltage protection, D5 from input to VCC prevents the pin from going above VCC+0.5 V and D6 from input to ground prevents it from going below -0.5 V. (Where ±0.5 is approximate.)
R22 because the diodes can’t clamp the voltage if CV_IN connects directly to a voltage source, and it limits diode current so a short doesn’t blow a diode out.
Thank you, always learning. This makes sense.
I built the current version of the arpeggiator with the internal resistors, only note B doesn’t work at all for me, I checked everything several times, all connections are correct! I think there is something wrong with the Arduino code for D13! Anyone else having problems with this?
You can test D13 by writing a simple sketch that sends a high followed by delay and a low to that pin (or some other pattern) and measure the output voltage change on the pin.
Hi everyone.
I am working on a revision for my schematic.
The current is here :
I would like to protect the pitch output with a buf op-amp.
I tested to put a TL071 as a buffer on a different project using a MCP4725 (following @twinturbo
circuits ) but there’s some drops in the voltage sometimes … Right now, it’s really unpredictable so I don’t know if it really comes from my circuits or from the eurorack power.
But I didn’t connect the floating pins of the TL071 to the ground. Might it correct the problem?
On the Texas Instrument datasheet, the NC pins are noted as “Not To Be Connected”. But I don’t know if it should remain unconnected or not.
If I play a little with the TL071 (pushing it a little bit right or left) I am able to reproduce the voltage drops.
Thanks for your help 
Hey, when you say drop in the voltage, are we talking slow or fast ones ? Slow ones for me would suggest power supply stability issue, fast one could be noise.
On the buffered amp, did you use small resistors, 100r, and decoupling capacitors ?
Thanks for your answer @Bpbby
I tend to forget to put decoupling capacitors and small resistors around my op-amp buffers … Is it really a bad thing?
Drops are slow … I think I might put to much modules on my eurorack power ( 3 arduinos & 1 daisy seed might be too much ?). Maybe I should test with less modules to see if the drops are constant …
The decoupling helps removing electronic noise, but i am not sure it would help in your case.
You seem to be good at coding arduino, you could use another one to record the voltage over a period of time. You would see how big are the drops and if they have some patterns (frequency, etc…)
You could maybe try powering the arduino with another psu (phone charger style)
I have a big module (my clone of the DFAM) that is not great at keeping the pitch stable. I am sure it is because of my psu not being great for that one, plus some voltage leakages here and there… gives some uniqueness and character
When the datasheet says not to connect them, you don’t connect them.
Bypass caps probably will have minimal effect, but might help keep high frequency noise from being a problem. But should not affect the behavior you are describing.
Sounds like a bad DIP socket.
@Bpbby haha, yes the arpeggiator tends to fluctuate a bit but it sounds more like an old analog synth, which is fine. In this case the voltage drops is like 1,2 or even 3 semitones, which is huge !
@analogoutput I will try to change the DIP socket then. The ones I use are really (too) cheap, I think some could be bad …
Getting rid of the TL071 have the effect of stabilize the voltage out from the DAC. One last field of exploration might be the position of the module in the power rack. I use the last socket on the rack, might it affect the power distributed to the module ?
