Blinkenlights?

On a sunny day (Mon, 16 Apr 2018 19:40:17 +0100) it happened Gareth's Downstairs Computer wrote in :

What do you nean by 'blinkenlights'? You can hang anything you like on GPIO (with proper hardware driver).

Was brought up on PDP11 and PDP8 and miss the ability, on the few occasions when necessary, to drill right down to the machine itself. Blinkenlights is a (fairly standard in alt.folklore.computers) reference to a front panel with binary lamps and switches.

What I anticipate is using one Pi to drive the JTAG on another.

Well, the Sense HAT has a well-supported set of switches and lights. There?s probably no general ?interface? you can build for it to access the entire complexity of the underlying Linux OS, but you could certainly use it as a base for some kinds of high level blinkenlights projects.

--
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A traditional set of blinkenlights is impossible, the bus lines aren't exposed where you could attach lights (and they switch a bit too fast).

That should be possible.

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Steve O'Hara-Smith                          |   Directable Mirror Arrays 
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You'd need over 2,000 LEDs to show all the registers of an ARM8

Disagree: at least one microcomputer (the IMSAI 8080, as seen in the "War Games" movie) had them way back in the mid-70s - and that was based on an Intel 8080, so it must have been possible to write a firmware monitor to emulate the effect of the handswitches and lamps on a PDP-8. However, the

8080 was an 8-bit chip with 8 nregisters and 16 bit addressing, so at least the number of switches and lights was manageable.

But do it on a 64 bit chip with 16 32 bit registers and a 32 bit address space? Some how I don't think so.

I have used hand switches to patch device drivers on 1900 mainframes (24 bit words, 22 bit address space) and that involved more than enough switches as far as I was concerned.

If the OP wants a real challenge, I suggest he builds something like the discrete transistor re-implementation of a 6502 that was recently donated to the NMOC. However, since that's been done, why not tackle something a little bigger and better, like a MC6809 MPU, but with at least one 6810 memory chip, 6820 PIA and 6850 UART. These would let the resulting wall of LEDs interact with its visitors via contemporary devices like a Wyse terminal and an Epson MX-80 printer.

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Depends on how hard-core you are. Remember the IBM 360/75?

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There are kits for PDP-8s and soon PDP-11s

There are others for Altair, etc.

Rob

Yes that processor had the address and data bus exposed on wires and ran at about 2MHz.

Yep but the registers weren't on disply only the address and data busses.

Especially since the address and data busses are not exposed on pins where you can connect to them but buried deep inside the SOC.

--
Steve O'Hara-Smith                          |   Directable Mirror Arrays 
C:\>WIN                                     | A better way to focus the sun 
The computer obeys and wins.                |    licences available see 
You lose and Bill collects.                 |    http://www.sohara.org/

On a sunny day (Mon, 16 Apr 2018 21:14:42 +0100) it happened Gareth's Downstairs Computer wrote in :

Ah, I remember the PDP11, was IIRC my first encounter with Unix. But the word 'blinkenlights' is new to me, I am in different language country. Seems to be German-English ?? 'blinken' and 'lights'.

That is simple to realize, connect some LEDs (via series resistor) to GPIO pins, you got at least a byte, and use the other pins to multiplex. Maybe if you want to do it the big way with hundreds of LEDs:

I bought that display in the army surplus, basically shift registers and LED drivers... Had to modify it a bit... to connect to GPIO.

Pi has JTAG? I must be getting rusty. On my site you find a raspi JTAG driver for an FPGA proto board:

I would not have an "underlying Linux OS", for I'm very much a Not Invented Here kind of softy :-)

Follow the example of the PDP8 where a rotary switch selected which system registers are displayed, or else the PDP11 where the registers appeared as though memory addresses.

Certainly hard core here; I have 7 4K core memory planes remaining from my first attempt at building a computer (TTL, own instruction set)

45 years ago?

Started out with 96 of them in two blocks of 48 from a Marconi Leo, reduced to only 8, then someone in Didcot wanted a plane to experiment with, so just keep the remaining 7 in my mini museum.

I never used them anyway! Got hold of 4 off 256 by 1 static rams and frigged a 128 by 8 bit memory; 128 bytes more than sufficient to satisfy the excitement of having your own computer back in 1973!

You can get kits of look a like switches, lights, etc to emulate a PDP11 control panel, the LEDs are even driven to emulate filament bulbs. But I guess this isn't what you want.

--
Cheers 
Dave.

I have one of these kits, awaiting assembly ...

But wnat I wish is to educate myself with an in-depth knowledge of the ARM8 instruction set, including its binary encodings for when I pick up the threads of an of-interest-to-me language development that I put to bed 30 years ago, now that I'm retired with nothing to do, and all day to do it in!

The world of 64 bit has arrived in the home laboratory, and I feel it to be time to do away with all computers where you have to spend some time programming your way around the limitations of them; including

32bit ARM with its 4GB address limitations!

(The worst cases in my experience being the 8051 and the 6303; both encountered during my professional life as a real-time softy!)

With 4 processing units, and oodles of cache levels, not to mention pipelined processing, that wouldn't be feasible anyway. I had one of John Miller Kirkpatrick's (RIP) SCAMP kits based upon the SC/MP processor which used clever tricks to give a memory blinkenlights approach, but that was only feasible with a single processing unit with a static processor whereby the memory cycle could be extended indefinitely. (Not possible with the Motorola chips which were dynamic)

It's Dog German as practised in Britain, similar in principle to Dog Latin where what is written bears a passing resemblance to the language being dogged but is not part of that language.

eg, in Dog French, "Pas deux leur Rhone que nous" a homophone for, "Paddle your own canoe", ie, "Mind your own business" :)

Thanks for that, a much simpler approach to getting a large number of LEDs, already laid out in nice straight lines!

I hope so, the ARM A53 certainly has then in its spec.

I've already obtained 100 lever operated microswitches and when I resurrect the 3D printer from 3 years ago, will be set up to make the toggles.

But no, I don't want a PDP11, just its style, to give me low level access to the Pi3.

On a sunny day (Tue, 17 Apr 2018 10:07:03 +0100 (BST)) it happened "Dave Liquorice" wrote in :

Yes, hard to tell what he wants, if he wants to set registers and the program counter by hand... I did it with dip switches once on a Z80 system, programming in binary. To me asm is a high level language.... C is one level higher, and C++ is a crime against humanity. The whole old Z80 system circuit diagrams and CP/M clone I wrote is still on my site:

However, since things simply move on, it all went with the garbage one day. Some people like old cars, I am not one of those. And I do not design tube amps anymore either :-)

The fun was in the doing it at that time, repeating the same thing over and over again is a no no for me.

If he really wants to see registers etc in ARM then there are cool disassemblers, you can get gcc to output asm too.

I still program a lot in asm for small micros like PIC micro controllers:

There is a lot you can do with 256 bytes of ram and a few kB FLASH:

These days for the simplest things bloated code is written using bloated languages by people that have no clue of the hardware, or even how a computer works.

I really do think some ASM hardware embedded programming should be required for programmers. It would save a lot of energy consumption and cost, reduce glowballworming. :-)