PiDP-1 - addendum 2026

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The standoffs from Mark arrived today (3!), so I wasted no time removing the electronics from the console case to solder in the last LED. I was careful to ensure placement of the last LED as well as lead orientation, then taped it in place and soldered it into position.

A final confirmation was done by powering up the Raspberry Pi and running '/opt/pidp1/test.sh' to see all LEDs working with the electronics sitting bare on the desk.

Then the electronics were installed in the rack operator panel and final assembly of the rack was completed.

I received an email from Oscar today, detailing the use of the speaker tabs and correct placement. I looked at my rack and saw the tabs were not in the correct place at all.

With care I removed the backing nuts from the top back of the speaker panel, then removed the tabs and buttoned up the top of the panel again. I then removed the two bottom back nuts and installed the two tabs in the correct location, ensuring they interlocked with the slots in the operator panel.

The finished assembly looks good and the tabs work as designed.

At the moment I have nowhere handy to mount the PiDP-1 rack. I can't mount it on a wall as I do need to access the switches on the operator panel, and this can't be done with any current wall mount. I hope to eventually mount it on the front of my 19in music synthesizer rack, but the PiDP-1 is narrower than a 19in rack and so must be attached some other way. The music rack is also full of synths, so I need to mount the PiDP-1 in front of the synths. At the moment it's not clear how I can do this, but I'm certain it will require fabrication of some type of mounting system.

In the meantime, I attached the frame standoffs to the rack in order to create a flat sitting 'test bed' for the PiDP-1. This allows it to sit flat on my work table so that I can finish final testing and configuration of the PiDP-1, incuding testing the I/O panel and getting the speakers working and configured, and testing the USB paper tape panel functions.

Ever since building the frame of the PiDP-1, I knew that finding a home for the finished kit would be a challenge. As stated before, it can't really be mounted on a wall because I need to access the switches, and this isn't possible with wall mounting in my office. I thought about mounting it on my existing music (synth) rack, floating in front of the synths, but that is a 19in rack and the PiDP-1 is narrow enough that fitting it poses several challenges, each inviting some type of rube-goldberg construction.

One thought I had early on was something I've seen but never owned - a rolling mid-height rack with tilting upper frame. These were often used for mult-track mixers or reel-to-reel tape decks. I even thought about buying one several years ago when I was playing with an 8-track 1/2in multi-track reel-to-reel tape recorder, but the cost was too high (over $200 for most options).

Yesterday in marketplace I saw an ad for the exact rolling 'mixer rack' I had wanted, and the asking price was $30. It was too good to pass up, so I messaged the owner today and then drove over and picked it up. It's used but in good shape, and perfect as a mobile home for the PiDP-1!

I found my 19in 1U spacer pieces yesterday, but could not find any of my hardware (clips or bolts), so I ordered some.

Today I fixed one caster that was loose, and then attached the 19in rack spacers to the rack using twist ties, which turns out to be quite solid, then placed the PiDP-1 rack onto the music rack, using the 1U spacers to support top and bottom, and finally twist-tying the mounting lugs on the PiDP-1 frame to the cross-bar at the top of the music rack.

I am very happy with this display/operation arrangement. It looks really nice, and is portable which is important in this room. It's not powered on at the moment, but almost compete and ready to go.

I've also ordered a 7in HDMI screen that I plan to mount on the surface of the paper tape panel, and that should come this week.

For some time now I've experienced an issue with the PiDP-1 related to power. I am using a CanaKit 27W PD power supply that I bought in 2024 when I purchased this Raspberry Pi-5, and which has worked without issue until now. The same Pi-5 and supply has worked perfectly without issue on the PiDP-10 I built in the summer of 2024.

The problem occurs with the rack PiDP-1. Whenever I turn on the sound amplifier which is connected to the Pi via USB dongle, I get a dreaded 'lightning bolt' icon with a warning indicating low power has been detected by the Pi-5. After much testing, it only occurs if I turn on the amplifier, and always occurs shortly after I turn on the amplifier. It's worst if I'm running the blinky lights demo program as that exercises the most lights, but it will always turn up no matter what program I'm running.

The solution according to the PiDP-1 forum is to buy a newer 'official' 45W Raspberry Pi power supply. They aren't all that expensive, but shipping from some places is almost as much as the cost of the supply! Fortunatley Digikey has reasonable shipping, so I ordered one tonight and switch when it arrives.

I am also having a sound issue, which may or may not be related to the power supply issue. Essentially, I have not been able to get sound at all from the audio dongle sound to work at all. Although diagnostics clearly show the audio dongle is plugged in and functional, it will not produce sound no matter how I try and enable it. Only the HDMI sound seems available.

Unfortunately, there is no actual HDMI monitor or sound on the Pi-5. Instead, to preserve screen resolution under VNC, I use an HDMI 'dummy plug' which fools the Pi-5 into thinking there's a hi-res HDMI monitor attached. I think this is also fooling the audio sub-system.

My solution is to add a 7in HDMI monitor to the rack. I have decided to purchse an Elecrow 7in HDMI monitor that features speakers, and will use that for my sound instead of the audio dongle.

It is possible that with a proper HDMI sound system, I will also be able to switch to the USB audio dongle and drive the panel speakers. That will be determined once I have the HDMI monitor working and also have the 45W power supply (so no low power warning!).

The Elecrow 7in HDMI monitor arrives tomorrow. I will mount it above the surface of the paper tape panel rather than cut into it as some have done. It has back mounting hardware so I should be able to drill small mounting holes in the paper tape panel to mount it securely.