Back panel questions

[terry-...@glaver.org]

Now that I have my PiDP-11 going (aside from the Examine switch, which is trivial) I'm working on "buttoning up" the case. I ordered the Ethernet, HDMI, and USB power extension cables from the Adafruit links on the project page, and they arrived today. The USB to TTL serial adapters are on back-order with no ETA. I have a few questions and observations:

1) What is the suggested orientation of the back panel on the PiDP? White or blue protective film face on the outside? Orientation of the panel?

2) Presumably the panel is plastic due to the ease of getting it laser cut. That does mean there's a pretty thick piece of plastic keeping the connectors from seating fully - I'm having some issues with the HDMI extension, presumably because of an incomplete connection due to this. It would be great if there were some front-mount extensions instead of rear-mount, so the connector faces would be flush with the outside face of the panel.

3) The suggested micro USB power extension doesn't line up with the mounting holes in the back panel - you may want to check this for future orders and adjust the spacing. Perhaps Adafruit is using a slightly different connector now? Alternatively, if you used a different extension, can you let me know what it is so I can order one?

4) Who would you suggest as a reliable alternate supplier for the USB to TTL adapters, if Adafruit doesn't restock soon?

5) Can you post a parts list for the optional quad serial TTL to RS-232 option? I assume it is a regular MAX232 and the stock charge pump caps. but would like to be sure before I order them.

I'm thinking of routing the TTL serial console (P5) into one of the MAX232 channels to get a true RS-232 serial VT102 console, then using 2 of the Adafruit USB to TTL adapters (if they get back in stock) on two of the other MAX232 channels for 2 more VT102 terminals. I'll extend the remaining 2 Pi USB ports to the back panel for keyboard + mouse. 

[oscarv]

Terry,

On Friday, July 6, 2018 at 3:27:13 AM UTC+2, terry-...@glaver.org wrote:

1) What is the suggested orientation of the back panel on the PiDP? White or blue protective film face on the outside? Orientation of the panel?

The block of serial ports should be on the right side, looking from the back.

 

2) Presumably the panel is plastic due to the ease of getting it laser cut. That does mean there's a pretty thick piece of plastic keeping the connectors from seating fully - I'm having some issues with the HDMI extension, presumably because of an incomplete connection due to this. It would be great if there were some front-mount extensions instead of rear-mount, so the connector faces would be flush with the outside face of the panel.

Yes, but then the connector blocks would stick out a bit. It should not be too hard to cut the slots wider if you need them to be, it's just (white) perspex.

3) The suggested micro USB power extension doesn't line up with the mounting holes in the back panel - you may want to check this for future orders and adjust the spacing. Perhaps Adafruit is using a slightly different connector now?

I need to check, I got the official dimensions from Datapro (https://www.datapro.net/products/hdmi-panel-mount-extension-cable.html?utm_campaign=relprods&utm_source=hdmi-dual-panel-mount-f-f-cable&utm_medium=product). They have a whole range of panel-mount connectors, and as far as I know the dimensions should be standard. But 'as far as I know' might be incorrect. I was not too worried as cutting a bit off the plastic would always be feasible.

5) Can you post a parts list for the optional quad serial TTL to RS-232 option? I assume it is a regular MAX232 and the stock charge pump caps. but would like to be sure before I order them.

You need the chip plus five capacitors. Best order the newer MAX202. It has the same pinout but needs smaller caps. Although it does not really matter much, a MAX232 is fine too. Just check the data sheet of whatever MAX you buy for the right capacitor values. 

I'm thinking of routing the TTL serial console (P5) into one of the MAX232 channels to get a true RS-232 serial VT102 console, then using 2 of the Adafruit USB to TTL adapters (if they get back in stock) on two of the other MAX232 channels for 2 more VT102 terminals. I'll extend the remaining 2 Pi USB ports to the back panel for keyboard + mouse. 

Makes sense, that was my idea! Sadly, I only have one proper VT series terminal...

Note that Aliexpress carries these PL2303HX cables, often for $1.80 including shipping. They are the exact same units.

Kind regards,

Oscar.

[Mark Matlock]

   I bought a number of the Adafruit extender cables but found that the depth of the case was not quite deep enough so I built a case extender from a shelf board made of particle board material. (see attached photos). I used the plastic back panel as a template and extended the depth 40 mm. I was able to drill holes matching the back panel and then use 3 inch long size 10-24 screws that screw into the plastic case and hold things together quite well.

   One positive aspect of this modification is that the weight of the extension makes it easy to flip switches firmly to insure the switch internal mechanism actually flips as well, without having to hold the case with my other hand. Also, I no longer need the wooden base, but I did attach three small stick on rubber feet to the bottom of the injection molded case to be sure it would not get scratched or damaged.

The current back panel fits on the case fine but the ethernet cut-out and the power cord hole are a bit low and are partially blocked. In the past I had a plastic panel laser cut to fit my full-size BlinkenBoned PDP-11/70 console and am thinking about having a custom panel cut. Oscar, if the design for the back panel were available I'd love to take the current cut-outs and move them around a bit. If I had used a thinner wood this would not be necessary but I wanted the thickness so the screw holes did not weaken the corners. Super glue was used to stick it the extender together.

Best Regards,
Mark

[Jodie Hobson]

I also purchased the Adafruit extender cables. My solution to the case not being deep enough to mount the USB and Ethernet cables on the back panel was to modify the cables. I cut the strain reliefs off the back of the bulkhead connectors which allowed me to bend the cable at a sharp 90 degree angle at the back of the connector. I then wrapped some electrical tape over the cable to act as a bit of strain relief.  The network cable also required a bit of the cable sheathing to be removed to get a tight enough bend. The photos below are of the network connector.

The connector on the micro USB extender cable is small enough that it does not require modification. The connector on the HDMI extender cable is so large that removing the strain relief would not provide sufficient clearance. 

I have ordered  a version B right angle HDMI connector from bluejeanscable.com. If it fits between the Raspberry Pi and the top of the PiDP11/70 case I may modify the back panel to accommodate it. 

[oscarv]

Mark,

On Friday, July 13, 2018 at 3:19:06 PM UTC+2, Mark Matlock wrote:

Oscar, if the design for the back panel were available I'd love to take the current cut-outs and move them around a bit. If I had used a thinner wood this would not be necessary but I wanted the thickness so the screw holes did not weaken the corners. Super glue was used to stick it the extender together.

Here are the latest files. If you want I can ask my laser cutter to make a custom one, should not be too expensive (guess $20 for a one-off, now he gets regular orders...). 

Kind regards,

Oscar