An Emulator of the Busch 2090 Microtronic Computer System for Arduino Uno and Arduino Mega 2560
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… and discussion of Busch Microtronic 2090. Courtesy of Barbara Nostheide, Nostheide-Verlag (Publisher and Copyright Holder).
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README.md

README.md

Busch-2090

An emulator of the Busch 2090 Microtronic Computer System for Arduino Uno R3 and Arduino Mega 2560

Author: Michael Wessel

License: GPL 3

Hompage: Author's Homepage

Contributer: Martin Sauter (PGM 7 Code)

Version: 3.2

YouTube Videos

Abstract

This is an emulator of the Busch 2090 Microtronic Computer System for the Arduino Uno R3 and Arduino Mega 2560.

The Busch 2090 was an educational 4bit single-board computer system of the early 1980s, manufactured by the company Busch Modellbau in Germany. There is some information about the Busch 2090 Microtronic available here, including PDFs of the original manuals in German.

The designer of the original Busch Microtronic, Mr. Jörg Vallen of Busch, was also so kind to grant permission to include a full copy of the manual set in the manuals directory of this project.

Busch 2090 Microtronic Emulator for Arduino Mega 2560 Version 3

Busch 2090 Microtronic Emulator for Arduino Mega 2560 Version 3

Busch 2090 Microtronic Emulator for Arduino Uno

Busch 2090 Microtronic Emulator for Arduino Mega

Busch 2090 Microtronic Emulator for Arduino Mega

See busch2090.ino or busch2090-mega.ino, or busch2090-mega-v3.inosketch for further instructions, and see the emulator in action here.

This project consists of two sketches. The main emulator code is in busch2090.ino for the Uno, and busch2090-mega.ino or busch2090-mega-v3.ino for the Mega 2560. The EEPROM has to be initialized properly before running the emulator. Please load and run PGM-EEPROM.ino for the Uno version, and PGM-EEPROM-MEGA.ino for the Mega version(s) first. The EEPROM is loaded with example ROM programs to be loaded into the emulator via the PGM key.

The busch2090-mega-v3.ino is the Busch Microtronic Mega emulator version 3. This version uses different hardware, and it is meant to be housed in a case. In addition, it supports the Emic 2 TTS Speech Synthesizer module. The Emic 2 module is optional, as is the SDCard shield. However, Mega version 1 currently requires the SDCard shield (will be updated soon).

Also, you will find some programs in the software directory. See below for instructions how to use them, and for a brief explanation of the .MIC file format.

Acknowledgements

Many thanks to Martin Sauter for retrieving and entering the original code of PGM 7, the Nim game. It works!

Hardware Requirements

For the Uno version, busch2090.ino:

  • An Arduino Uno R3
  • A TM1638 module with 8 7segment digits, 8 push buttons, and 8 LEDs
  • A 4x4 keypad with matrix encoding for hexadecimal input

For the Mega 2560 version, busch2090-mega.ino, you will need

  • An Arduino Mega 2560 R3
  • A TM1638 module with 8 7segment digits, 8 push buttons, and 8 LEDs
  • A 4x4 keypad with matrix encoding for hexadecimal input
  • An LCD+Keypad shield
  • An optional Ethernet+SDCard shield

For the Mega 2560 version 3, busch2090-mega-v3.ino, which is meant to be housed in a case, you will need

  • An Arduino Mega 2560 R3
  • A 4x4 keypad with matrix encoding for hexadecimal input
  • A 3x4 telephone keypad, for function buttons and DIN input, NOT matrix encoded
  • 8 LEDs and matching resistors (for 5 V)
  • 4 pull-down resistors for DIN digital inputs (typical 10 kOhms)
  • 4 standard signal diodes for DOT digital outputs to prevent leakage currents from external electronic circuits / experiments connected to the outputs
  • 8 N.O. momentary push buttons
  • A power switch
  • 2 Adafruit 7Segment LED backpacks
  • 2 potentiometer, one for LCD contrast (100 Ohms), one for CPU speed (200 Ohms)
  • A 4x20 LCD display, standard Hitachi HD44780
  • A laser-cut (or laser-printed?) face place. The blueprint / layout is in the faceplate directory of this project.

The following components are optional for the Mega version 3:

  • Ethernet+SDCard shield (see #define SDCARD)
  • Emic 2 TTS Speech Synthesizer module (see #define SPEECH)

Please refer to this image for an explanations of the layout and functionality of the front panel:

Mega Emulator V3 Front Panel Explanation

Wiring

For the Uno version:

TM1638 module(14, 15, 16);

byte colPins[COLS] = {5, 6, 7, 8};
byte rowPins[ROWS] = {9, 10, 11, 12}; 

#define DIN_PIN_1 1
#define DIN_PIN_2 2
#define DIN_PIN_3 3
#define DIN_PIN_4 4

#define RESET_PIN 0

#define CPU_THROTTLE_ANALOG_PIN 5 // connect a potentiometer here for CPU speed throttle control
#define CPU_THROTTLE_DIVISOR 10 // potentiometer dependent 
#define CPU_MIN_THRESHOLD 10 // if smaller than this, delay = 0

For the Mega 2560 version 1:

LiquidCrystal lcd(8, 9, 4, 5, 6, 7);

TM1638 module(49, 47, 45);

byte rowPins[ROWS] = {37, 35, 33, 31}; 
byte colPins[COLS] = {36, 34, 32, 30}; 

#define DIN_PIN_1 22 // digital input pins read by DIN instruction 
#define DIN_PIN_2 24
#define DIN_PIN_3 26
#define DIN_PIN_4 28

#define RESET_PIN 53

#define CPU_THROTTLE_ANALOG_PIN 15 // connect a potentiometer here for CPU speed throttle control
#define CPU_THROTTLE_DIVISOR 10 // potentiometer dependent 
#define CPU_MIN_THRESHOLD 10 // if smaller than this, delay = 0

// these are analog values read from the LCD+Keypad shield, adjust if necessary 
// the read analog values must be greater than these, they are lower bounds: 
#define NOTHING_KEY 1000
#define SELECT_KEY  770
#define LEFT_KEY    540
#define DOWN_KEY    360
#define UP_KEY      160

For the Mega version 1, please note that you will have to clip or disconnect PIN 10 from the LCD+Keypad, otherwise the SDCard will not function properly. I am using extension headers for this (just bent PIN 10 out of the way such it doesn't make contact). See this image:

Bent Pin 10 of LCD+Keypad Shield

For the Mega 2560 version 3 - there is more freedom how to set up the hardware, but I did it as follows:

 // 
 // optional components
 //

 #define SPEECH // comment out if no Emic 2 present
 #define SDCARD // comment out if no SDCard shield present 

 //
 // SDCard chip select pin 4 
 // 

 #if defined (SDCARD)
   #define SDCARD_CHIP_SELECT 4
 #endif
 
 //
 // serial interface Emic 2 TTS module
 //

 #if defined (SPEECH)
    #define RX_SPEECH A8
    #define TX_SPEECH 53
 #endif
 
 //
 //   
 //

 #define RESET  47 // soft reset 

 #define BACK   63
 #define RIGHT  64
 #define UP     65
 #define DOWN   66
 #define LEFT   67
 #define CANCEL 68
 #define ENTER  69

 //
 // status LEDs
 //

 #define DOT_LED_1 55
 #define DOT_LED_2 56
 #define DOT_LED_3 57
 #define DOT_LED_4 58

 #define CLOCK_LED     39
 #define CLOCK_1HZ_LED 41
 #define CARRY_LED     43
 #define ZERO_LED      45

 //
 // 1 Hz clock digital output
 // 

 #define CLOCK_OUT 6

 //
 // DOT digital output
 //

 #define DOT_1 5
 #define DOT_2 3
 #define DOT_3 2  // we need pin 4 for SD card!
 #define DOT_4 18 // PIN 1 didn't work for hardware experiments, probably serial 

 //
 // DIN digital input
 //

 #define DIN_1 17
 #define DIN_2 16
 #define DIN_3 15
 #define DIN_4 14

 //
 // telephone keypad buttons for DIN input
 //

 #define DIN_BUTTON_1 42 // telephone keypad # 
 #define DIN_BUTTON_2 44 // telephone keypad 9 
 #define DIN_BUTTON_3 46 // telephone keypad 6
 #define DIN_BUTTON_4 48 // telephone keypad 3 

 //
 // remaining telephone keypad buttons
 //

 #define CCE  26 // telephone keypad *
 #define RUN  28 // telephone keypad 7
 #define BKP  30 // telephone keypad 4
 #define NEXT 32 // telephone keypad 1
 #define PGM  34 // telephone keypad 0 
 #define HALT 36 // telephone keypad 8 
 #define STEP 38 // telephone keypad 5
 #define REG  40 // telephone keypad 2 

 //
 // CPU speed throttle potentiometer
 //

 #define CPU_THROTTLE_ANALOG_PIN A0
 #define CPU_THROTTLE_DIVISOR 10   // potentiometer dependent 
 #define CPU_MIN_THRESHOLD 5       // if smaller than this, CPU = max speed  
 #define CPU_MAX_THRESHOLD 99      // if higher than this, CPU = min speed 
 #define CPU_DELTA_DISP 3          // if analog value changes more than this, update CPU delay display 

 //
 // for initialization of random generator
 //

 #define RANDOM_ANALOG_PIN A5

 //
 // LCD panel pins
 //

 LiquidCrystal lcd(13, 12, 11, 7, 9, 8); // we need pin 10 for SD card!

 //
 // 2 Adafruit 7Segment LED backpacks
 //

 Adafruit_7segment right = Adafruit_7segment(); // at address 0x71
 Adafruit_7segment left  = Adafruit_7segment(); // at address 0x70 

 // right.begin(0x71);
 //  left.begin(0x70);

 //
 // HEX 4x4 matrix keypad
 //

 #define ROWS 4
 #define COLS 4

 char keys[ROWS][COLS] = { // plus one because 0 = no key pressed!
 {0xD, 0xE, 0xF, 0x10},
 {0x9, 0xA, 0xB, 0xC},
 {0x5, 0x6, 0x7, 0x8},
 {0x1, 0x2, 0x3, 0x4}
 };

 byte colPins[COLS] = {37, 35, 33, 31}; // columns
 byte rowPins[ROWS] = {29, 27, 25, 23}; // rows

 Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

This picture might provide some ideas how to set up / wire the hardware:

Busch 2090 Microtronic Emulator for Arduino Mega 2560 Version 3

Also notice that there is a blueprint of the faceplate in the faceplate directory of this project.

Description

For the Arduino Uno and Mega version 1, the TM1638 module is used. The push buttons of the TM1638 are the function keys of the Microtronic, in this order of sequence, from left to right: HALT, NEXT, RUN, CCE, REG, STEP, BKP, RUN:

#define HALT  1 
#define NEXT  2 
#define RUN   4
#define CCE   8
#define REG  16
#define STEP 32
#define BKP  64
#define PGM 128 

The 4x4 keypad keys are hex from 0 to F, in bottom-left to top-right order. You might consider to relabel the keys on the pad (I haven't done that):

7 8 9 A       C D E F 
4 5 6 B  ==>  8 9 A B
1 2 3 C  ==>  4 5 6 7
* 0 # D       0 1 2 3

For the Arduino Mega version 3, there is another (non-matrix encoded) telephone keypad being used, for function buttons. The mapping is as follows:

1 2 3       NEXT  REG DIN4
4 5 6  ==>   BKP STEP DIN3
7 8 9  ==>   RUN HALT DIN2
* 0 #       C/CE  PGM DIN1

Microtronic's Carry and Zero flag are the LEDs 1 and 2 of the TM1638, the 1 Hz clock LED is LED 3 (from left to right). The LEDs 5 to 8 are used as DOT outputs (set by the data out op-code FEx). On the Mega version 3, there is no TM1638, but discrete LEDs are used instead. See below.

Notice that the Arduino reset button will erase the emulator's program memory. To only reset emulator while keeping the program in memory, connect Arduino pin D0 (RX) to ground (or D53 for the Mega version 1, or D47 for the Mega version 3, which also has N.O. push button for that purpose).

The Arduino Uno pins D1 to D4 (or D22, D24, D24 and D26 on the Arduino Mega version 1, or the telephone keypad keys #, 9, 6, 3 and pins D14 to D17 on the Mega version 3), are read by the Microtronic data in op-code FDx (DIN). Connecting them to ground will set the corresponding bit to

  1. See PGM D. On the Mega version 3, different pins are used, see below.

Analog pin A5 on the Uno (or A15 on the Mega version 1, or A0 on the Mega version 3), is used as a CPU speed throttle. Connect a potentiometer to adjust the speed of the CPU.

Unlike the original Microtronic, this emulator uses the leftmost digit of the 8digit FM1638 (or of the left Adafruit LEDs backpack display on the Mega version 3) to display the current system status (the original Microtronic only featured a 6digit display). Currently, the status codes are:

  • H: stopped
  • A: enter address
  • P: enter op-code
  • r: running program
  • ?: keypad input from user requested
  • i: entering / inspecting register via REG
  • t : entering clock time (PGM 3)
  • C : showing clock time (PGM 4)

Also unlike the original Microtronic, the emulator uses blinking digits to indicate cursor position. The CCE key works a little bit differently, but editing should be comfortable enough.

Typical operation sequences such as HALT-NEXT-00-RUN and HALT-NEXT-00-F10-NEXT-510-NEXT-C00-NEXT etc. will work as expected. Also, try to load a demo program: HALT-PGM-7-RUN.

On the Mega Version 3.2., also the single step execution and breakpoint functionalities are also implemented (function keys STEP and BKP). These functions are not yet implemented on the older Mega Version 1 and Uno version (I still have to sync back some changes from Mega Version 3 to these older code bases).

Note that programs can be entered manually, using the keypad and function keys, or you can load a fixed ROM program specified in the Arduino sketch via the PGM button. These ROM programs are defined in the busch2090.ino sketch as PGM7 to PGMD macros.

The Mega version 1 uses the select button (either the LCD+Keypad shield for Uno version and Mega version 1, or the discrete N.O. button with the Mega version 3) to toggle between PC + current op-code display, register display, extra-register display, and display off. Notice that the emulator slows down considerably with LCD being turned on.

Program Counter and Op-Code Display Register Content Display

For the Mega version 3, I have used a telephone keypad for the function buttons:

#define CCE  26 // telephone keypad *
#define RUN  28 // telephone keypad 7
#define BKP  30 // telephone keypad 4
#define NEXT 32 // telephone keypad 1
#define PGM  34 // telephone keypad 0 
#define HALT 36 // telephone keypad 8 
#define STEP 38 // telephone keypad 5
#define REG  40 // telephone keypad 2 

The remaining 4 buttons can be used to provide digital input to DIN command; in addition, there are also real digital inputs reserved for hardware experiments:

#define DIN_BUTTON_1 42 // telephone keypad # 
#define DIN_BUTTON_2 44 // telephone keypad 9 
#define DIN_BUTTON_3 46 // telephone keypad 6
#define DIN_BUTTON_4 48 // telephone keypad 3 

#define DIN_1 17
#define DIN_2 16
#define DIN_3 15
#define DIN_4 14

Note that on the Mega version 3, all digital inputs are set to INPUT_PULLUP, with the exception of these DIN_1 to DIN_4, for which external pull-down resistors have to be used:

pinMode(DIN_1, INPUT); 
pinMode(DIN_2, INPUT);
pinMode(DIN_3, INPUT);
pinMode(DIN_4, INPUT);

The DOT output LEDs are discrete LEDs, and so are carry and zero flags, 1 Hz clock, and CPU clock:

#define DOT_LED_1 55
#define DOT_LED_2 56
#define DOT_LED_3 57
#define DOT_LED_4 58

#define CLOCK_LED     39
#define CLOCK_1HZ_LED 41
#define CARRY_LED     43
#define ZERO_LED      45

For hardware experiments, there are additional outputs for DOT as well:

#define DOT_1 5
#define DOT_2 3
#define DOT_3 2  // we need pin 4 for SD card!
#define DOT_4 18 // PIN 1 didn't work for hardware experiments, probably serial 

and there is an additional output for clock 1 Hz:

#define CLOCK_OUT 6

The faceplate has four holes under the DOT LEDs for one pair of DIN-DOT input-output cables, and three more holes to the right, for 9 V VCC, GND, and 1 Hz clock cables.

Since there is no LCD+Keypad shield being used, there are discrete N.O. buttons that take on these functions (SD card):

#define BACK   63
#define RIGHT  64
#define UP     65
#define DOWN   66
#define LEFT   67
#define CANCEL 68
#define ENTER  69

Load and Save Files to SDCard (Mega versions only)

The Mega version supports saving a memory dump to SDCard via PGM 2. Currently, the SDCard+Ethernet card shield is mandatory in Mega version 1, but optional in Mega version 3. The LCD+Keypad shield offers a primitive file name editor. Use Select key to confirm current file name; Left and Right keys to move cursor, Up and Down keys to change character at cursor position.

With the Mega version 3, there is no keypad, but discrete N.O. buttons (see above) take on the functions for SD card operations.

Files are loaded from SDCard via PGM 1. Here, the LCD+Keypad shield is used to browse through the directory of files. Use Select key to confirm selection, and Left key to abort loading.

Load Program from SDCard Save Program to SDCard

The .MIC File Format and Example Programs

The software directory contains some programs from the Microtronic manuals and from the book "Computer Games (2094)". With the Mega version, you can put these files on a FAT16 formatted SDCard, and load them via PGM1. Please refer to the original manuals on how to use these programs.

In .MIC file, in addition to hexadecimal instructions, you can find comments (a line starting with #), as well as the origin address instruction @ xx. This means that the instructions following @ xx will be stored from address xx on. Most of the time, you will find @ 00 at the beginning of the file. If a .MIC file does not contain a @ xx, then the program will be loaded at the current PC. That way, programs could be relocatable (e.g., for subroutines). Also, a .MIC can contain more than one @ xx. An example is the DAYS.MIC program.

There are a couple of programs in the Microtronic Manual Vol. 2 which require incremental loading of parts, i.e., first load DAYS.MIC, and then additionally load WEEKDAY.MIC. The programs automatically load at the correct addresses.

The example programs in the software directory have been automatically converted from the above linked PDFs with the help of an OCR (Optical Character Recognition) program, so they may contain some strange characters and OCR artifacts and errors. Not all programs have been tested by the author yet. Programs which have been successfully tested contain a # tested comment. To compensate for OCR artifacts, the .MIC loader recognizes an extended character set for hexadecimal input, e.g., not only 1, but also I and l are accepted for 1, the O character is accepted for 0, etc.

PGM Demo Programs are Stored in EEPROM

For the Uno version, please run the PGM-EEPROM.ino sketch first, and use PGM-EEPROM-MEGA.ino for the Mega versions. This will load example programs into the Arduino's EEPROM. The emulator won't initialize correctly otherwise.

The programs stored into and loaded from the EEPROM are PGM 7 to PGM C:

  • PGM 0 : self-test not yet implemented.
  • PGM 1 : on Mega, this loads a program memory dump from SDCard. Use LCD+Keypad shield to select file via Select key, Left key to abort loading.
  • PGM 2 : on Mega, this saves a complete memory dump to SDCard (.MIC file extension is used). The LCD+Keypad shield offers a simple filename editor. Use Left and Right to change cursor position, Up and Down to change character at cursor position, and Select to confirm and save. The files are stored as text. You can also use a simple text editor to create files (CR+LF end of line coding), and load them back via PGM 2. Whitespace is ignored.
  • PGM 3 : set time / clock (not a real program, i.e., nothing is loaded into program memory for this function)
  • PGM 4 : show time / clock (not a real program, i.e., nothing is loaded into program memory for this function)
  • PGM 5 : clear memory
  • PGM 6 : load F01 (NOPs) into memory
  • PGM 7 : the Nim game as documented in the Microtronic Manual Vol. 1, page 7. Many thanks to Martin Sauter for retrieving the code from an original Busch Microtronic and contributing it to this project!
  • PGM 8 : crazy counter
  • PGM 9 : the electronic die, from Microtronic Manual Vol. 1, page 10
  • PGM A : the three digit counter from Microtronic Manual Vol. 1, page 19
  • PGM B : moving LED light from Manul Vol. 1, page 48
  • PGM C : digitial input DIN test (port input output echo)

Optional Emic 2 TTS Speech Module for Mega Version 3

If enabled, the Emic 2 speech module will echo back and confirm function and HEX keypad presses. In addition, the navigation buttons of the file browser trigger the following functions:

  • Left : describe current system status.
  • Right : describe content of 7segment display
  • Up : general Microtronic emulator information
  • Down : emulator software version
  • Cancel : get an answer from the Magic 8-Ball
  • Back: listen to HAL 9000

Also, activities such as loading a PGM or SDCard program, clearing the program memory, displaying or setting the time, are spoken.

Emic 2 Built-In TTS Module / Mega Version 3

Occasionally, the Emic 2 crashes and simply stops talking. Then, only a full power-cycle will revive it.

The built-in Emic can also be accessed programmatically be means of Microtronic machine instructions, and hence be made to speak arbitrary sentences. The MOV xx / code 0xx instructions are being used for this purpose. The effect of a MOV xx instruction is to copy the contents of register x onto itself, so these instructions are basically vacuous, redundant NO-OPs. An extra meaning / extra effect is given to them in the Mega version 3. Here, a MOV xx sends a (high- or low) nibble x to the built-in Emic 2. A full ASCII character with decimal code xy (e.g., 65 for character A) is thus sent via 0xx, 0yy (e.g., 066, 055 for character A), in "most significant nibble first" order. Notice that these nibbles are decimal nibbles though, not hexadecimal nibbles. Hence, x can take values from 0 to C (ASCII goes from 0 to 127, and 12 = C - not all ASCII characters are speakable, of course - in fact, all characters below 32 are ignored, with the exception of carriage return, ASCII code 13). Decimal coding is used in order to make entry of ASCII character codes more convenient. Notice that Emic requires a heading S as well as a trailing carriage return (ASCII code 13). An ABC from the Emic 2 hence takes the program 088 033 066 055 066 066 066 077 011 0033. Consequently, the Microtronic program memory can store 126 characters max.

Required Third-Party Libraries

The emulator requires the following libraries, which are the work of others, and which are included in the library subdirectory:

  • Keypad library
  • TM1638 library - note that this is a modified version of the original one
  • TM16XXFonts for alphanumeric 7segment display fonts
  • EEPROM library

For the Mega version 1, the following standard libraries are used, and already part of the Arduino distribution (version 1.6.6):

  • TM16XXFonts from the TM1638 library
  • LiquidCrystal library
  • SPI library
  • SD library
  • String library

The SD and String libraries were responsible for memory leaks and terrible system instability. I hence removed them in Mega version 3, and switched to the fabulous SdFat library which works much more reliably.

For the Mega version 3, the following standard libraries are used, and already part of the Arduino distribution (version 1.6.6):

  • TM16XXFonts from the TM1638 library
  • LiquidCrystal library
  • SPI library
  • SoftwareSerial to talk to the Emic 2 TTS module

These additional Adafruit libraries are required to drive the 7Segment LED SPI backpack displays. They are available from the Adafruit homepage:

  • Adafruit_LEDBackpacklibrary
  • Adafruit_GFX library

In addition, instead of the SD card library, the

  • SdFat library.

Future Work

  1. Sync back latest changes from Mega version 3 into Mega version 1 and Uno version.