SuburbanBoy

understanding Wilba's panel pcb

11 posts in this topic

i intend to design a pcb for a mbseq.

i have some trouble understandung the following:

acccording to this schematic (mbseq_v4_din.pdf) i would need 7 serial registers (74HC165) for 54 buttons, but wilba's pcb (wilba_mbseq_pcb.pdf) uses only 2 of them for 58 buttons.

as i have problems to read the layout well, i can only see that 4 switches are connected parallel per shift register's pin.

i guess there is some trick done with the diodes and the 74HC595 on the other side of the switch to achieve some kind of multiplexing, but i can't follow that path in the layout.

is there some documentation on that? or can someone put it in easy words for the noobs.

i haven't yet looked the source code about it. i just don't want to get lost looking for something that isn't there. so any feedback if i should follow that path is welcome.

and: if i end up having enough space for 11 74HC165s to connect 53 knobs and 17 encoders on the pcb, would multiplexing be worth the effort, except for the gain of endorphines, serotoines etc. in the engineer's brain parts? (that's more or less a metaphorical question.)

have a nice day!

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is there some documentation on that? or can someone put it in easy words for the noobs.

If you are able to understand German look at and the two subsequent ones.

And yes, "multiplexing" is worth the effort, because it saves a lot of hardware and real estate on the PCB. And the software for this has already been implemented, so it comes for free. Why don't you simply order a PCB from SmashTV?

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If you are able to understand German look at and the two subsequent ones.

och, ich schau da immer nicht rein. aus gründen. vielleicht sollte ich die überdenken.

And yes, "multiplexing" is worth the effort, because it saves a lot of hardware and real estate on the PCB. And the software for this has already been implemented, so it comes for free. Why don't you simply order a PCB from SmashTV?

weren't you the one who designed a custom panel, too? ah, i see.

simple answer: it's a matter of design.

many thanks, i will study the source code and then have a further look onto the hardware design.

btw, i noticed on the sammichFM it's the other way 'round. ten LEDs controlled by one of each chips.

Edited by SuburbanBoy

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I'd suggest you look at the schematic, not the board layout. That is much easier to grasp :smile:.

Edit: Sorry, I just realized that this schematic is for the MB-6582, not the MB-SEQ.

Edited by ilmenator

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I'd suggest you look at the schematic, not the board layout. That is much easier to grasp :smile:.

Cool and useful schematic. Thread hijack: is a similar schematic available for the MB6582? I could use it :whistle:

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Cool and useful schematic. Thread hijack: is a similar schematic available for the MB6582? I could use it :whistle:

Well, my bad - the schematic I linked above is actually for the MB-6582, and not for the MB-SEQ. :whistle:

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My MB-SEQ PCB is basically a combined switch/LED matrix for all the LEDs and switches (1x 74HC165 for inputs, 74HC595 for LED outputs, 74HC595 for matrix "column" sinks), plus dedicated 74HC165 for the encoders, since MIOS doesn't (didn't?) support encoders in a switch matrix, and even if they did, the routing would have been insane... it is actually a lot neater by having the 74HC165 close to the four encoders it is handling.

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I'd suggest you look at the schematic, not the board layout. That is much easier to grasp :smile:.

nah, i owe you at least one nervous breakdown i'll miss while re-engineering. thumbsup.png

and thanks for the additional info, wilba.

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i just realised that i shouldn't have stopped reading after "MIDIO 128 and MIDIBox " here. whistle.png

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i just realised that i shouldn't have stopped reading after "MIDIO 128 and MIDIBox " here. whistle.png

That is actually kind of the MIDIbox mantra: read, read, read, then read some more... not always easy to convey to newbies without sounding bigheaded, though :whistle: .

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That is actually kind of the MIDIbox mantra: read, read, read, then read some more...

i know that. and there's definately hardly any blind spot in the documentation. but we all know (i guess there is a common sense about it) that the huge amount of data is not well structured. i don't blame anyone for that, i know how time-consuming such a task is.

but you somehow have to cope with that fact, and leaving stuff out is an option. sometimes with unwanted side-effects. logik.png

not always easy to convey to newbies without sounding bigheaded, though :whistle: .

don't worry. i actually find the communication in the forums here to be very civilized.

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