pidp8i-test "Reading the switches"

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Thomas Runge

Feb 8, 2022, 3:24:56 AM2/8/22
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I'm currently assembling my pidp8i kit.

The board is populated without the switches and I'm running the pidp8i-test program. All LEDs are fine, but coming to the "Reading the switches" part, I see following pattern from the start:

0037 0037 0037

The assembly guide says: "Temporary at December 2019: if the switch values come out as 0037 0037 0037: are you using a Pi 4? Not a hardware problem. You didn't add the Pi 4 software patch. See the linked page in section 1, it tells about installing the Pi 4 patch from the Fossil repository. Please email me if you're confused about how to do it!"

I'm actually using a Pi 4. Wondering if the above is still valid in 2022? Also, I haven't been able to find a link to the proposed "Pi 4 software patch".

Can anybody help out here, please?

Thomas Runge

Feb 8, 2022, 10:39:08 AM2/8/22
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Just soldered on the switches, and apart from seeing the above mentioned pattern with no switches enabled, I receive some kind of feedback from all switches,

BUT activating switches SR8 - SR12 and SING_INST does not give any feedback.

Steve Tockey

Feb 8, 2022, 4:31:07 PM2/8/22
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"I'm actually using a Pi 4. Wondering if the above is still valid in 2022?"

Yes, it is still valid today. The root issue has to do with the GPIO header and how it works differently between the Pi 4 and all of the other versions. This thread of messages should be the starting point for getting the background info:

"Also, I haven't been able to find a link to the proposed "Pi 4 software patch"."

Hopefully this thread should be able to at least get you started:

Apparently the trick is to just use a different version of I thought that the standard install process now automatically addresses this. Are you installing the latest version of PiDP-8/I tagged v20210214?

I hope this helps,

-- steve

Thomas Runge

Feb 9, 2022, 3:16:06 AM2/9/22
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Hello Steve,

Thanks for your valuable feedback. Highly appreciated!

With the second link I was able to resolve the issue. pidp8i-test and (more important) pidp8i seem to work as expected after running the described procedure there.

Still, I'm somewhat astonished that this is not highlighted anywhere on (or am I missing something?). Actually, from what I read there, it seems the multi-core version V2021.02.14 (which I have installed over here) should work on a Pi 4: "1. Multi-core version, v2021.02.14 — This OS image is built with the incandescent lamp simulator which only works properly on the multi-core Raspberry Pi 2, 3, and 4 boards. (All models.)".

Given that this is a known issue for more than two years, and that it is documented everywhere that pidp8i is working on "[...] any version from Pi Zero to Pi 4 [...]" this was quite some surprise...

Thanks again for pointing me into the right direction,
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