I have some of these regulators but I do not like them a lot because of its bulky potentiometer. I always find hard to have a reliable and stable voltage.
I prefer the one like this
@stojos, compared to the one you’ve linked, these regulators are adjustable, so you can give a little bit more than 5V (I use 5.15V)
And regarding keeping ZynthianMini cheap: you may consider using SMD components and PCB assembly service. They (at least JLCPCB, the one I really use) have usually have good prices on components, especially the basic resistors and cap. Components you won’t have to purchase from different sources with all the associated fees.
I had a quick look at mcp23017: they are cheaper in SSOP package at JLCPCB (1.31$) then on Aliexpress in DIP package (couldn’t find one less then 3.00$).
Anyway, for the integrated PSU I think a ready made module like above is the best way to go.
I have already spent a lot of time redesigning it with smd components. As soon as you go into smd design it would be stupid to not include dac from V5. In any case, you can not get switches and encoders soldered in factory cheaply - they are on the other side of PCB from smd components. So decision would need to be made either to leave them for manual soldering or separate them into different PCBs and get cables which I don’t like. I was also looking into option to not have switches at all - just encoders and their switches. Soldering just encoders is much easier then 20 buttons. All this is debatable.
I am also thinking is it worth adding PSU component and power switch and have option for people to use wide range of DC power supply (v5 approach) that they have at home or simple just add PSU connector and power switch but demand only to connect 5V 8A DC power supply that is less then 10£ on aliexpress.
I was even contemplating putting zynthian mini on top of Behringer 204HD. They have very similar dimensions. I like that front and back plate of Behringer are removable and can be attached to a zynthian mini 3d printed case.
All these option have their own pros and cons. Finding the best balance that will fit a need for many is very hard.
For riban modular I get PCBs with the SMD components fabricated then manually install and solder the switches and pots for the same reason that fabrication of these through-hole components is too expensive and relatively easy to manually do in the lab. It is the kind of thing you could let the hobbiest build.
For the prototype of riban modular I used a 5V PSU directly connected to the system but for the production model I will build a proper PSU section to decouple whatever crap someone plugs into it. Never trust your users to always act sensibly!
I use the self same Buck converter for all my Pi’s so far. Not tried it on a Zynth Pi5 yet.
Beware they arrive set to 9Volts which was directly responsible for the demise of a Pi Zero W on Saturday. Make sure to adjust them BEFORE plugging it all up. First Pi I’ve bricked since starting all this mucking around.
In terms of Zynth power supply. I’ve long lusted after a controlled Power off, so I actually know the last thing the zynth does after recieving a power off command is actually turn off the power with a high side P channel MOS-FET powering the Zynth. It obviously has to come up active as well. Battery supplies benefit from this and it allows a level of Power supply control the Pi itself doesn’t provide.
I also sling a decent sized diode in line with the Power line to prevent the inevitable barrel connector power and polarity misunderstandings. STTH5L06.pdf (560.2 KB)
Some kit ( I don’t know about Eurorack) can be very fussy about reverse polarity.
Maybe solution for this would be to add pcb mounted usb-c connector and switch. So the benefit is that it is very unlikely that something else than 5V will be supplied though usb-c and zynthian will have power switch compared to when using rpi’s usb-c connector that requires cable to be un-pluged and plugged again to start after shutdown.
Talking about this subject after shutting down zynthian my rpi 5 stays warm - led is switched from green to red . Power switch would definitely turn it off but is it normal for rpi to take so much energy when in shutdown state that it is still warm ?
a kernel patch (I didn’t investigate if this was merged in Raspi kernel or in mainline Linux), that add an extension called NUMA wich increase computing perfs
another patch for raspi 3 wich reduce power consumption when idle
This is not officialy supported by Raspberry pi but, from what I’ve read in different places, seems to be totaly functionnal. With a simple argument in config.txt, you can switch the PCIe lanes to operate in 3.0 mode vs 2.0 by default. This speed up SSD almost two time compared to the default setting.
