I’m a not a Zynthian owner. Not yet. New to this forum as a member. For the past weeks I have read several threads here. What a great project this is.
I found the Zyntian a while ago read quite some forum posts and now I’m ready to build a Zynthian. From scratch. I mean that I didn’t order the kit, because I’m forced to do it as cheap as possible. So no easy to use pcb as the kit offers, but regular prototype board. And a Pifi Dac+ instead of a HifiBerry (but I will create a Hifiberry account anyway, just to vote for Zynthian )
Which are the schematics I should use for my build? The schematics on the wiki don’t seem to be the same as used for the pcb’s in the kit. Or do I misunderstand?
These capacitors are not “critical” but “convenient”. They debounce the encoder/switch signal and avoid that software debouncing algorithm consumes “high priority” CPU cycles (ISR). I recommend to use some kind of hardware debouncing circuitry with the encoders and switches, but you can ignore my recommendation and your Zynthian probably will work without problems
Are schematics for a debouncing circuitry available? I can solder and sort of read schematics, but I can’t design them. Why are the schematics different from the PCB’s in the kit ?
How can I know how often the software debouncing algorithm is invoked? And how much CPU time is used by the algorithm?
I built my zynthian ‘classic’ with the larger debounce capacitor swapped with one of the smaller values and occasionally when turning that encoder fast there is a little hanging, I’ve also built a zynthian with no capacitors or ( the HIFI berry Amp + for zynthian spotters…) and I’ve had no problems. Might be different in a high electrical noise environment or with longer wires… .
Well, I almost never had to put hardware debounce on rotary encoders in my projects… just one time I needed a low pass filter (something like the second schematic on this page http://www.dream-dimensions.de/2015/10/using-rotary-encoders/ ) but just because the firmware reading the encoder was stupid enough to crash with signals too fast
The debouncing circuit in the kit’s PCb consist of 3 capacitor from the 3 signal encoder pins to ground. For the switch pin 100nF and for the 2 encoder pins, 10nF. I will fix the wikiw schematics ASAP
2 Observations, regarding the All in One schematic:
The encoder pin assignments seem to have changed from earlier versions,
old SW: pin 4, all in one SW: pin 2
old A: pin 2, all in one A : pin 4
(had an initial setback mixing old & new docs. re-implementing the circuit in my own layout)
High level signal levels of the MCP23017 I/O Expander are 4.3V (VDD – 0.7 min) with a 5V supply shown in the schematic, the SDA, INTA, INTB outputs seems to exceed Pi safety limits some have published. Short term encoder testing seems OK running the chip at 3.3V.
The pin numbering convention is reversed in the All-In-One schematic. It’s a convenience question, but not a “real” change This is addressed with the JST connectors, that enforce the right connection. Sorry for the confusion
Yes. I’ve thought about this before, but i preferred to maintain these voltage levels in the All-In-One circuit because it worked perfectly in the older 2in1 circuit (and certainly it works perfectly in the newer All-In-One). Anyway, if you can verify that it also works with the lower voltage levels, i will change it in future versions.
)
)
This is addressed with the JST connectors, that enforce the right connection. Sorry for the confusion 