PiDP-8/I Software

Changes To Incandescent Thought
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Changes to "Incandescent Thought" between 2017-08-02 05:15:28 and 2017-10-15 00:38:26

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# The Situation

In February 2016, Norman Davie released a program he called [Deeper Thought](https://groups.google.com/forum/#!msg/pidp-8/tbciVNoZJbw/AMjywRKLAwAJ), after an earlier program by Steve Gibson called [Deep Thought](https://www.grc.com/pdp-8/deepthought-sbc.htm). The most important difference between these two programs for our purposes here is that instead of running as PDP-8 code within the simulator, as Gibson's program does, Davie's Deeper Thought runs as a native program on the Raspberry Pi, using a version of Oscar Vermeulen's original `gpio.c` module to manipulate the LEDs on the PiDP-8/I's front panel and read its switches.
In February 2016, Norman Davie released a program he called [Deeper Thought](https://groups.google.com/forum/#!msg/pidp-8/tbciVNoZJbw/AMjywRKLAwAJ) after an earlier program by Steve Gibson called [Deep Thought](https://www.grc.com/pdp-8/deepthought-sbc.htm). The most important difference between these two programs for our purposes here is that instead of running as PDP-8 code within the simulator, as Gibson's program does, Davie's Deeper Thought runs as a native program on the Raspberry Pi, using a version of Oscar Vermeulen's original `gpio.c` module to manipulate the LEDs on the PiDP-8/I's front panel and read its switches.

Davie's program has been [forked several times](https://github.com/timdawg/Deeper-Tought-2/network), but this mode of operation remains in all of the versions I've tried.

When Ian Schofield created the [incandescent lamp simulator](/wiki?name=Incandescent+Lamp+Simulator) for the PiDP-8/I, he changed the external interface in a couple of ways which prevented it from being used with any of these versions of Deeper Thought.

Now, about a year after the initial release of Deeper Thought, we finally have a version of the ILS that works with Deeper Thought.


# Modifying `deeper.c`

The first thing you have to do to build any version of Deeper Thought against the current version of the PiDP-8/I software is copy its `deeper.c` file into the PiDP-8/I software's `src` subdirectory.
The first thing you have to do to build any version of Deeper Thought against the current version of the PiDP-8/I software is copy its `deeper.c` file into the PiDP-8/I software's `src` subdirectory:

    $ cd ~/pidp8i                  ⇠ or wherever the PiDP-8/I source code is
    $ cp /path/to/deeper/thought/deeper.c src
You need to make a few adjustments to `deeper.c` to get it to build:

Use your favorite Linux text editor to make a few adjustments to `src/deeper.c` to get it to build:

1. Add the following line between the big block comment at the top of the file and the `#include` lines following it, at line 156 or so:

        #include "gpio-common.h"

2. Remove the these lines, found up among the `#include` lines:
2. Remove these lines, found up among the `#include` lines:

        extern void *blink(void *ptr); // the real-time multiplexing process to start up
        extern uint32 ledstatus[8];     // bitfields: 8 ledrows of up to 12 LEDs
        extern uint32 switchstatus[3];  // bitfields: 3 rows of up to 12 switches

3. Replace the block of code beginning with the `pthread_create()` call and ending with `sleep(2)`, inclusive, with the following:
3. Replace the block of code beginning with the `pthread_create()` call and ending with `sleep(2)` — inclusive — with the following:

        pidp8i_simple_gpio_mode = 1;
        if (start_pidp8i_gpio_thread ("Deeper Thought 2") != 0) exit (EXIT_FAILURE);

With that done, you must reconfigure the software to get it to recognize that `deeper.c` has been added to the `src` subdirectory. If you reconfigure it on a multi-core Pi such as the Pi 2 or Pi 3, it will build against the ILS; otherwise, it will build against the NLS, which may look slightly different from the appearance you get from the old `gpio.c` module, but it probably isn't worth continuing unless you're simply curious.
With that done, you must reconfigure the software to get it to recognize that `deeper.c` has been added to the `src` subdirectory. If you're happy with your current configuration, this will do the trick:

    $ make reconfig

Otherwise, re-read `README.md` and run `configure` manually:

    $ ./configure --with-your-new-option-set

Either way, among the lines in the `configure` script output should be this one:

    Found Deeper Thought; building it against ILS GPIO module

If you reconfigure it on a multi-core Pi such as the Pi 2 or Pi 3, it will build against the ILS; otherwise, it will build against the NLS, which may look slightly different from the appearance you get from the old `gpio.c` module, but it probably isn't worth continuing unless you're simply curious.

Now you can try saying `make`. If the software builds, you can now run it as `sudo bin/deeper`.

If you want to install it, I recommend that you build and install Deeper Thought in the normal way, then copy the `bin/deeper` executable you built above over the top of the normal one. This lets you leverage the rest of the installation process shipped with Deeper Thought, such as installing the `deeper` system service.


# Why Not Make This Easy?
︙