The Microwriter MW4 was an innovative early hand held computing device with a chording keyboard, first demonstrated in the late 1970's.
Manuals for this device may be found here:
- https://www.microsoft.com/buxtoncollection/a/pdf/microwriter%20new%20users%20guide.pdf
- https://www.microsoft.com/buxtoncollection/a/pdf/Microwriter%20General%20Systems%20Manual.pdf
I own one of these devices and extracted the EPROM contents. This repository contains a simple emulator for the Microwriter MW4 and some additional tools. If you have, or are able to construct, a Microwriter keyboard then you may connect that via a serial port and use the keyboard to enter data. You will need an Arduino UNO R3, or similar. The code for reading the keyboard is provided in this directory.
It is also possible to pass key codes to the emulator on the command line.
I contacted Chris Rainey (chris@bellaire.co.uk), co-inventor of the Microwriter MW4 and he was kind enough to allow me to publish the EPROM image alongside this emulator. Please note, this permission is granted for non-commercial use only.
This emulator works under Linux, I'm using Debian Buster.
You will need the following packages:
apt-get install build-essential picocom
A simple Makefile is used to build all of the components. The following builds the emulator:
make microwriter
Perform an initial test, like this:
./microwriter -r microwriter.rom -d -c $(./text_to_codes hello world)
Your terminal should clear and then you should see the following:
+ @ @@ @@ @@ @ @ @
+ @ @ @ @ @ @ @@ @@
+ @ @ @@ @@@ @ @ @@@ @ @ @@@ @ @@ @ @@ @ @ @ @
+ @ @ @@ @ @ @ @ @ @ @ @ @ @ @ @@ @ @ @ @@ @ @
+ @ @ @ @ @@@@@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
+ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
+ @@ @ @ @@@ @@@ @@@ @@@ @ @ @@@ @ @@@ @@@ @ @
+
+
+
+@@@@@
As you can see, there are a number of flags on the command line.
-r microwriter.rom # The emulator opens the EEPROM image contained in microwriter.rom
-d # Causes the emulator to send an embedded sequence of keys which force sensible defaults
-c # Clear the screen every time a new display is rendered, otherwise the display scrolls
Any remaining arguments are treated as key codes. The key codes are hexadecimal values reflecting the pattern of keys on the chording keyboard. Those patterns are summarised in a file called letters in this directory. Some scripts have been provided which allow key codes to be generated easily, for example:
[542]% ./text_to_codes hello
0x11 0x08 0x19 0x19 0x04 0x10
It's convenient to embed that conversion on the command line (see initial test, above).
The Microwriter manuals, reference above, describe command sequences. These are used to control the state of the device and have a dedicated key (positioned under the thumb at the bottom left hand side of the keyboard). The command sequences are similar to letters but with the dedicated key depressed. An additional script has been provided to simplify command sequence entry. As an example, page 32 of the New User's guide describes a sequence of keys used to erase everything from the device. The command sequence is shown as [M][W][M][K] and the following command generates key codes for that:
[38]% ./command $(./text_to_codes mwmk) ; echo
0x2f 0x2b 0x2f 0x22
Putting that into the emulator, like this:
[39]% ./microwriter -r microwriter.rom -d -c 0x2f 0x2b 0x2f 0x22
Results in the following output:
+@ @ @@@@@ @ @ @@@ @@@@ @ @ @@@ @ @@@@@ @@@ @@@@ @@@@@ @@@ @
+@@ @@ @ @@ @@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
+@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
+@ @ @@@@ @ @ @ @ @@@@ @ @ @ @ @@@@ @ @ @@@@ @@@@ @ @ @
+@ @ @ @ @ @ @ @ @ @ @ @ @ @@@@@ @ @ @ @ @
+@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
+@ @ @@@@@ @ @ @@@ @ @ @ @@@ @@@@@ @@@@@ @ @ @ @ @@@@@ @@@ @
+
+
+
+ @@@@@
+
+
The memory has been cleared.
If you would like to make an interface to the keyboard using an Arduino, the following instructions will help you to install the required tools.
Connect your Arduino to a USB port on your computer and flash the device. If your Arduino is not connected to /dev/ttyACM0 then you will need to make appropriate adjustments to the Makefile. You may choose to examine the output from the dmesg command in order to check the device name for the Arduino.
[560]% sudo make clean flash
rm -f serial_keyboard.hex serial_keyboard.elf serial_keyboard.o microwriter
avr-gcc -Wall -Os -mmcu=atmega328p -c serial_keyboard.c -o serial_keyboard.o
In file included from serial_keyboard.c:4:0:
/usr/lib/avr/include/util/setbaud.h:222:4: warning: #warning "Baud rate achieved is higher than allowed" [-Wcpp]
# warning "Baud rate achieved is higher than allowed"
^
avr-gcc -Wall -Os -mmcu=atmega328p -o serial_keyboard.elf serial_keyboard.o
rm -f serial_keyboard.hex
avr-objcopy -O ihex -R .eeprom serial_keyboard.elf serial_keyboard.hex
gcc -Wall -Wextra -g microwriter.c display.c cdp1802.c -o microwriter
avrdude -V -F -c arduino -p ATMEGA328P -b 115200 -P /dev/ttyACM0 -U flash:w:serial_keyboard.hex
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.00s
avrdude: Device signature = 0x1e950f (probably m328p)
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: reading input file "serial_keyboard.hex"
avrdude: input file serial_keyboard.hex auto detected as Intel Hex
avrdude: writing flash (288 bytes):
Writing | ################################################## | 100% 0.06s
avrdude: 288 bytes of flash written
avrdude: safemode: Fuses OK (E:00, H:00, L:00)
avrdude done. Thank you.
Here are a couple of pictures of the keyboard setup:
You will notice that the Microwriter keyboard connector is offset slightly. There's an unconnected pin which fits into the odd gap in the Arduino headers. Please look at the block comment in serial_keyboard.c for more detail.
You may want to test that this works correctly. If you connect using a serial terminal, hitting the enter key on your computer keyboard will trigger a scan of the Microwriter keyboard.
Here, I connect to the serial port and hit enter a few times while also pressing keys on the Microwriter keyboard:
[31]% sudo picocom -l /dev/ttyACM0 -b 115200 -q
110111
111110
111101
111011
110111
101111
011111
Before using the keyboard it is important to ensure that the baud rate settings are correct. If you have picocom (see apt-get, above) then the following command will do that:
sudo picocom -l /dev/ttyACM0 -b 115200 -r -X -q
Now you can run the emulator like this and enter keys using the chording keyboard:
./microwriter -r microwriter.rom -d -c -s
Press CTRL-C to exit. If that fails, try CTRL-Z and then kill the background process.
The cursor position looks wrong.
- cdp1802.c - A simple emulator for the CDP1802/COSMAC processor. This is not coded efficiently but I tried to make the code map over the instruction table in this document http://www.qq22.net/qq22/pdf/1802.pdf
- display.c - This is coded directly from the display controller data sheet below. Entering the pixel information was tedious.
- microwriter.c - Glues the CDP1802 emulator to the display and contains the main program loop.
- serial_keyboard.c - An Arduino program for reading the keyboard and sending key codes to the PC serial port.
- letters - A text file showing the letter shapes.
- text_to_codes - A script to convert text to key scan codes, uses the letters file.
- command - Converts letters to Command sequences which can control settings and configuration of the Microwriter
- The display controller https://datasheet.octopart.com/HD43160AH-Hitachi-datasheet-108301.pdf
- User manual for the CDP1802 http://bitsavers.trailing-edge.com/components/rca/cosmac/MPM-201A_User_Manual_for_the_CDP1802_COSMAC_Microprocessor_1976.pdf
- This is another, perhaps more efficient emulator for the CDP1802 https://github.com/wd5gnr/1802UNO