As I have an audio adapter now I wanna get back to my dual ksoloti spi setup.
Ksoloti 1 will be getting 5v from an old recycled axoloti DC part. It should then power ksoloti 2 through 5v and gnd being interconnected. Do I have to interconnect the Vbusend pin too to make this work?
VBusEnd handles cutting off the USB power in case DC is connected from another source. What I would do is tie VBUSEND to 5V on the 2nd Ksoloti, and leave the 1st Ksoloti as is.
This way you don’t have to worry about USB power supplies fighting each other while both Ksolotis are connected via USB.
The second Ksoloti will simply not receive any power from the USB port since it is already getting power from the first Ksoloti anyway (and there is no scenario where the second Kso should be on but not the first Kso).
Ok that makes sense, thanks!
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Hey I gave this a second thought, and I was wondering if this USB power fighting is really such an issue?
If they are connected to the same computer / usb hub it will be on the same 5v line anyway right?
I’m mainly asking because making an adapter that connects all 5 pins to the midi breakout part will be much easier without this weird cross connection between 5v and vbusend.
Or could even cross connect the incoming 9v on the dc / midi part, instead of the 5v on the ksoloti boards.
- I am scared connecting 5v to any pins on ksoloti, as most pins are not 5v tolerant and I think this could fry the board.
Hey just for clarity: does the 5v bus have to be interconnected when I have 2 linked boards?
Or could they also be powered seperately, as I describe here?
You’re right, if they have a common 5V power source (or separate USB power) it seems easiest to just power them separately as you described (and not connect any of their 5V pins together).
Ok thanks for clarifying. I have power for each of them seperately from a recycled Axoloti DC part through a guitar pedal board supply (9v 500ma)
Both ksoloti’s are chronically underpowered, sometimes going in the >4.5v range. I measure full 5v on the dc part but then 4.x on the ksoloti.
Any Idea why this could be?
I have a midi fighter twister and a novation launchpad attached to each of them. But I think the 9v supply should be plenty.
9v 500ma sounds a bit risky given that four “mini-computers” are powered by it.
Pedal power supplies are fine with multiple analog-style guitar pedals (those usually draw a few tens of mA) but digital stuff draws more. Also those midi controllers have lots of LEDs judging from online pictures.
Often power supplies do not deliver what is written on the specs. It might refer to a maximum/peak draw or it simply is a cheap supply that can’t be trusted. It is usually recommended to have a power supply that can deliver at least twice of the current you expect.
Ksoloti/Axoloti Core drew up to 90mA when I measured, and if the MIDI controllers draw anything similar you’re already at 90*4 = 360 mA. Much more if lots of LEDs are on.
This is a rough estimate, mind you, and should be taken with a grain of salt.
Fun fact: there is a way to measure rough current consumption on Ksoloti Core: Measure power draw of Ksoloti
Thanks for the answer.
This is PER board. I also power the launchpad seperately through an usb isolator (that is speced with 500ma at 5v), so that one doesn’t go into the equation.
So I think I’m well within the specs. If we do 390ma = 270ma and I have 1A supply. That is almost 3 times of what I need.
Also I have used the same setup for 2 axolotis for years.
I was wondering, could these jumper wires be a problem? Impedance?
I believe those shouldn’t be a problem. Hard to guess what is going on and what the exact power scheme is, if some power sources are shorted or any connection is draining the power supply …
The USB isolator has its own power supply?
How do you get 500mA per board, are you using more than one salvaged Axoloti power board? (Though it looks like the regulator on the Axoloti power board can supply up to 1.2A)
Yes I use 2 salvaged axoloti DC parts. You can see there is actually 2 stacked on top of each other.
Actually I just noticed that one of the jumpers was not fully in. No making sure it is plugged, Ksoloti says it’s on 4.8V. is that fine?
Tbh I don’t really love this shield/jumper wire combination. I think there is still room for improvement swapping out the pin headers for JST connectors. I just had to wait till the angled ones I ordered arrived.
But on the long run I would prefer a shield that directly attaches to the board. I’m going to a weekly synth DIY meetup to learn KICAD.