The Raspberry Pi +

November 2019

THIS PAGE IS OBSOLETE

(Building the Bare Metal version of Memu-Pi)

See this page for the current version of Memu-Pi

MEMU-Pi  : Now with Joystick Support

MEMU-Pi is Bill Brendling's idea for implementation of Andy Key's Memotech Emulator, MEMU, on a Raspberry Pi (RPi).

For a complete description of the functionality of MEMU, refer to the MEMU page on Andy's site.

Introduction

Bill's first MEMU-PI implementations were based on building the system on top of a base Linux (Raspbian) operating system. Restrictions of the Raspbian GPL License meant that a pre-built MEMU-PI system could not be distributed without breaching the Raspbian license terms; the procedure for building a system of your own was quite involved but full instructions for building MEMU-PI on Raspbian are archived on this page.

Making matters much simpler, Bill has now released a bare metal version of MEMU-PI. This does not require an operating system to be preinstalled on the PI, but, as with the GPL terms mentioned below for the Raspbian implementation, Bill's distribution includes some source files as he describes below in the bare metal MEMU-PI section.

Now that a bare metal version is available, most users are unlikely to want to run MEMU on top of a Raspbian installation, but the facility is there if needed. I have archived the original Raspbian page here. That page describes how to build Bill's MEMU-Pi from scratch, before the bare metal version was released.

Bare Metal MEMU-PI

(Description by Bill Brendling - February 2019)

I now have a genuinely bare-metal version of MEMU for the Raspberry Pi.   I can't claim any credit for the bare-metal part. I just took the "Circle" bare-metal environment produced by R. Stange:

• https://github.com/rsta2/circle
• https://www.raspberrypi.org/forums/viewtopic.php?f=72&t=90130  

 and ported MEMU to run in this environment.  

Since Circle is GPL licensed, to comply with GPL terms, the Zip file (see below) contains a cut down copy of the Circle distribution (missing all the samples and those add-on libraries which I did not use). MEMU is Public Domain software and as such, is compatible with GPL.

To run this version of MEMU, copy the contents of the "boot" folder onto a FAT formatted SD card, insert into RPi, connect keyboard and monitor and power up.

• To switch between the different MEMU windows press <Ctrll> plus a Function Key :

• The <SysRq> key brings up the configuration dialog

The equivalent of the MEMU command line is "/memu.cfg" (on the SD card). Note that the configuration dialog overwrites this file. I might add a second configuration file that is not overwritten for things like diagnostic switches.  

This version of MEMU can be compiled on Raspbian on a RPi. The "build" script in the top folder compiles everything three times to produce versions optimised for the different RPi processors. The actual MEMU source is in the "app/menu" folder. It could also be cross-compiled on an x86 Linux machine. See the Circle "README.md" file in the top folder.  

This is still a work in progress.

Running on Raspbian

Should you want to run MEMU-Pi on a Raspbian system, installation from the Circle distribution is pretty straightforward too :-

There are five different Raspbian executables. Simplest solution for these is to unzip the whole lot in a user home folder. The executables are then in the "memu-circle/app/memu" folder.

However, another option (if you don't want all the source), would be to first extract just the boot folder (and its sub-folders), then extract the five executables ("memu", "memu-cfg", "memy-fb", "memu-cfb", "memu-pi") from the "memu-circle/app/memu" folder into the already extracted "boot" folder.

Building The System (Optional)

The source code there will build six versions of MEMU on a Raspberry Pi. The first four versions will also build on x86 Linux. These versions are:

memu-circle/app/memu/memu:

This is the classic command line version of MEMU, but with additional features (see below). It requires XWindows, and is configured using the command line.

memu-circle/app/memu/memu-cfg:

This version also requires XWindows. Configuration is specified by a configuration file "-config-file memu.cfg" and a configuration dialog. Try <SysRq>, <Windows> or <Windows Menu> keys to open the dialog (not all environments pass all keys).

memu-circle/app/memu/memu-fb:

Command line version that does not require XWindows. Instead each window is shown full screen (using frame buffer). Use <Ctrl> plus function keys to switch between windows.

memu-circle/app/memu/memu-cfb:

Configuration dialog version that does not require XWindows.

memu-circle/app/memu/memu-pi:

Configuration dialog version that does not require XWindows. Uses GPU to display. Can use RPi GPIO to attach: MTX keyboard, Atari style joysticks, printer, PIO (Note only 3.3v not 5v). Specify hardware as "-hw-config hardware.cfg". Example file for MTX keyboard included.

memu-circle/boot/kernel*.img:

The bare metal versions for the different RPi processors. This version uses two configuration files "memu0.cfg" (static) and "memu.cfg" (changed by the configuration dialog). It supports use of GPIO to attach hardware (specify "-hw-config hardware.cfg" in "memu0.cfg"). At present this version does not use the GPU, nor does it provide DART emulation. More work to do. However it is currently the best one to use for MTX-Pi.

Functionality

All of these versions include:

CFX-II Emulation:

Enable this with "-cfx2 rom_file". The rom_file should be 16KB as Martin produces, it is automatically split into ROM 4 and ROM 5. CF partitions are specified as separate files, which means that the same files can be used as either SID drives or CF partitions. Specify the partitions as -cf-image c:p image_file", where "c" is card number (0 or 1) and "p" is partition number on the card (0-7).

 There is a technique to getting into CFX CP/M mode. First press and hold both the keys. Then press and hold the "C" key. Release the keys. Continue to hold the "C" key long enough for the CFX ROM to recognise CP/M mode required. This order is necessary because XWindows will not report the second key if the "C" is already down.

Enhanced keyboard re-mapping:

Enable this with "-kbd-remap". This now works as per the Propeller hardware interface. By default Andy's original mapping. Hit to make use of the three "missing" keys to match the shift state of most characters. to turn on so that keypad keys produce the digits as labelled. The "-kbd-remap" switch also applies the ROM patches to support the three extra keys.

Load and save audio (*.wav) files:

Enable this with "-cassette-in file" or "-cassette-out file". The files may be either *.wav or *.mtx. *.mtx files are converted to/from audio during load/save. Clearly this is much slower than the usual way of loading *.mtx files. To keep the file size down the attached Zip file only contains a couple of examples in the "tapes" folder.

Slightly improved usage message:

If there is an issue with the command line, it tells you which switch is causing the problem.

MEMU-Pi Operation

The image at the top of the page shows the screen output when MEMU-Pi boots in colour CP/M mode.

Note: when running CP/M, many of the programs available write to the emulated 40 Column MTX VDP screen, to switch between the 40 column and 80 column screen to be displayed on the RPi monitor, use "<ctrl> + <F1>" and "<ctrl>" + "F2" key combinations (it must be the left <ctrl> key).

MEMU-Pi Configuration Menu

The system can be configured using a configuration menu, invoked by either the "Sys Req" key or "Scroll Lock" (this alternative is required as X-Windows masks "Sys Req").

The menu is navigated with the cursor keys and the options selected with the <Space> bar.

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