More Blinkenlights

[Anthony Cunningham]

Before I commit to soldering the switches on to my PCB I have one question about the pattern of lights that is displayed when I'm running the Pidp8 simulator. As you can see from the attached picture the lights that come on are mostly in the top right-hand corner of the main group of leds. These lights flicker while the four to the left and the one in the bottom left-hand corner are on continuously. The lights in the right-hand section flicker.

Is this what should be displayed?

Thanks,

Tony

[Steve Tockey]

Tony,

What you are seeing is the light pattern for OS/8’s idle loop while it is waiting for user input from the console. So, congratulations, if it’s not exact then it’s very, very close. To be 100% sure, you should stop SIMH and run pidp8i-test:

From whatever terminal is the console for the PiDP-8/I, you should at this point be seeing OS/8s user command prompt, a period in the far left column. Type control-e (hold down control, type e while control is still down, release e, release control).. this should take you to the simh prompt:

simh>

Type exit at the prompt and hit return. This should take you to the prompt of Raspberry Pi OS which should be something like

home/pi/ $

At this prompt you can type pidp8i-test then hit return. This runs the full blinkenlight test program. You’ll see on the screen what it says it’s showing on the front panel. Something like

All lights on

All lights off

Row 1 on

Row 2 on

Row 3 on

…

Column 1 on

Column 2 on

Column 3 on

After that, it will go into a kind of race track pattern where only one light will be lit but it starts in the upper left and sequentially goes through every light. During this test, look for LEDs that are either always on or never on.

Also, after the switches are all soldered in, at this same point in the test program you can test the switches. Flipping a switch will cause an octal pattern to be printed out, one bit in the pattern should change according to the switch that got hit.

In fact you can test this without the switches by shorting the middle hole of a switch to the top hole of a switch using a bent piece of wire, like what you cut off from the resistors or diodes after you soldered them in.

When you are done with pidp8i-test, just control-c out of it back to the Raspberry Pi OS prompt. From there, you can do a normal shutdown of the Pi to solder the switches. From the Pi OS a prompt, you can also type pidp8i start followed by return. After 20-30 seconds you should see the OS/8 idle loop appear. After pidp8i start, then just type pidp8i then return and you should now see the OS/8 start up dialog on the terminal.

I hope this helps,

— steve

[Anthony Cunningham]

Thanks, Steve. All good now.

Tony