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Re: Yoshimi on the Raspberry Pi

Postby Martin Walker » Fri Nov 01, 2019 10:44 pm

Folderol wrote:The Pi itself does have insulated mounting holes. Also, the Audio out is on a fully insulated socket, and the USB and Ethernet sockets have clear space round them, so I can hard earth the case, but still float the Pi and all the attachments.

Sounds like a good plan again, and a common scenario in today's electronics - a decent screened enclosure, but no ground loop problems.

Are you going to fit a ground lift switch Will, for those whose remaining gear has two-wire mains cables and therefore no direct earth connection?


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Re: Yoshimi on the Raspberry Pi

Postby Folderol » Sat Nov 02, 2019 7:33 pm

Martin Walker wrote:Are you going to fit a ground lift switch Will, for those whose remaining gear has two-wire mains cables and therefore no direct earth connection?


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Prolly not. I don't think there would be any benefit, and because of the size and shape of the unit, if one was fitted it would have to be a slide switch - a small toggle is too easy to snap off.
Slides are a pig to make apertures for and fit :(
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Re: Yoshimi on the Raspberry Pi

Postby The Elf » Sat Nov 02, 2019 7:58 pm

I've ordered a Raspberry Pi 3 kit from Amazon that I intend to build with nephew over Christmas (it's our tradition to do a Christmas build). I intend to turn it into a Commodore 64, at least for a days' gaming fun!
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Re: Yoshimi on the Raspberry Pi

Postby Folderol » Sun Nov 03, 2019 8:24 am

The Pi 3 should handle that with room to spare - in fact it's a better choice than the Pi 4, as you can use a standard HDMI lead.
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Re: Yoshimi on the Raspberry Pi

Postby Folderol » Tue Nov 05, 2019 11:13 am

Hit a bit of a speedbump :(

I failed to allow for the height of the relay on the power control PCB, then Murphy saw his chance, when I reached up to get a ruler off the shelf, and accidentally nudged a full reel of solder. This fell off and (with great precision) landed directly on said relay, snapping its pins off.

I bodged it to continue tests on the design - all OK - but obviously need to rebuild with a different board layout and new relay. Of course, I didn't have enough stripboard for a new larger board, so more stuff ordered {sigh}.
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Re: Yoshimi on the Raspberry Pi

Postby Eddy Deegan » Tue Nov 05, 2019 11:49 am

Phew, I was worried for a brief moment that it was the Pi itself that was going to get damaged by the solder falling while reading that!

When I saw it was a relay I breathed a sign of relief, and although it's a bit of a setback it could have been worse!

Go go Will :-)
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Re: Yoshimi on the Raspberry Pi

Postby Folderol » Tue Nov 05, 2019 7:30 pm

Wounds licked, and a first pic with a paper template in the exact position of the revised PCB will be. The components shown on this are actually the other side of the board.

The white lead is the 12V supply for the monitor. It's sitting in a groove in the box. You can see the HDMI lead for it coming out from under the 'PCB' and that will sit in the other grove. The two small LEDs will indicate 'power applied', and 'running'. The USB audio module is glued to the case and when the Box is closed up plugs into one of the sockets on the Pi.

The lid is the right size - parallax :)
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Re: Yoshimi on the Raspberry Pi

Postby BJG145 » Wed Nov 06, 2019 9:21 am

Looking good! :thumbup:
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Re: Yoshimi on the Raspberry Pi

Postby Wonks » Wed Nov 06, 2019 9:58 am

Don't forget to leave some room to put the music in. ;)
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Re: Yoshimi on the Raspberry Pi

Postby Folderol » Wed Nov 06, 2019 7:01 pm

Wonks wrote:Don't forget to leave some room to put the music in. ;)
Now he tells me.
It's a bit late now, and unfortunately Yoshimi doesn't have a compressor.
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Re: Yoshimi on the Raspberry Pi

Postby Folderol » Wed Nov 06, 2019 9:25 pm

Progress :D
We now have the new control board which fits correctly and is fully tested.

As you can see I had to lie one cap on its side, otherwise it hit the (unused) USB C power socket. I normally put ICs in sockets, but if I had done that then it would also foul the stuff underneath - there really isn't a lot of space. In future I'll probably see if I can find a deeper 20 way socket, as that's what decides it.

The slit in the board is to ensure the mains pins of the relay are completely isolated from everything else. Also, on the underside, the tracks between the pins have all been removed. I'll probably glue a bit of plastic over the top of this, to provide a little protection for straying fingers.

Some final wiring tomorrow, then hopefully is software funtime :tongue:
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Re: Yoshimi on the Raspberry Pi

Postby Eddy Deegan » Wed Nov 06, 2019 11:05 pm

The package looks really tidy!

The form factor is perfect for desktop use and such a small package should be accommodatable in a workspace of any size.

Really impressed so far and looking forward to subsequent developments. As a synth man I'm relishing the prospect of Yoshimi goodness in my setup and I anticipate doing some lovely stuff with this :-)

Great work Will :clap:
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Re: Yoshimi on the Raspberry Pi

Postby Folderol » Fri Nov 08, 2019 7:05 pm

Another speedbump :(

The problem with emulation is that you need to be sure that what you're emulating really is equivalent to the real thing.

Up till now, I've been powering the unit from a bench power supply rather than the one installed in the unit. This is so that I can keep a watch on current levels while testing, and also stop the shutdown from actually shutting things down - in case I'd got it wrong and it tried to shutdown while the Pi was running full tilt.

It seemed to be working fine. That was until I watched the current demand while it was going through the emulated shutdown. The power control module was supposed to wait 7 seconds after the Pi itself had gone into standby before disconnecting the supply, but was actually doing so about a second afterwards - and not always quite the same time! I was using one of the GPIO lines to trigger shutdown, setting it 'high' in the knowledge it had to go low when the Pi had stopped - and this had worked perfectly every time when my emulated Pi stopped.

It turns out that the GPIO lines 'disconnect' a long (and variable) time before the Pi completes its tidying up :( However, the good news is that in the process, I discovered that the internal 3.3V supply does drop when the Pi goes into standby, reliably at that exact point. The result is my nice new PCB is no longer quite so pristine as it was before :tongue:

It all does work correctly now. The red power light comes on immediately the start button is pressed, and the green 'ready' light only comes on once the desktop is showing. When shutting down, the green light goes off immediately the process starts. Actual power off is 7 seconds after the Pi is completely dormant - at which point the red light goes out.

This delay is to ensure that the Pi and any attachments are all completely settled before being robbed of power.

It's all software from here on. In order to keep background services to the absolute minimum, automounting USB drives is not enabled, nor is networking. However I'm setting up a couple of basic Apps, to enable these when needed.

P.S.
Being in a metal box, wireless and bluetooth wouldn't work anyway.!
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Re: Yoshimi on the Raspberry Pi

Postby Martin Walker » Fri Nov 08, 2019 7:24 pm

Power down and up cycles can be notoriously difficult to second guess, so bravo Will :clap:

Don't get too complacent about the software side though - have a read of Eddy's latest bug-hunting post so you can feel the fear and do it anyway :beamup:


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Re: Yoshimi on the Raspberry Pi

Postby The Elf » Fri Nov 08, 2019 7:34 pm

:clap: :thumbup:
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