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ACORN ARCHIMEDES Keyboard
This covnerter makes Acorn Archimedes keyboard usable on modern USB computer.
Preassembled converter is available here.
Archimedes converter hardware is identical to 'TMK IBMPC[PS/2]', if you already have one you can try this just by changing firmware.
Discussion: https://geekhack.org/index.php?topic=121747.0
Source code: https://github.com/tmk/tmk_keyboard/tree/master/converter/archimedes_usb
Tested with A300 keyboard.
You can make your own coverter easily if you are familiar to AVR. Reset pin is optional.
Connector AVR pin
------------------------------------
,--_--. 1: Reset PD0
/ o6 5o \ 2: NC
| o4 3o | 3: GND GND
- 2o o1 - 4: 5V VCC
`-___-' 5: In(from keyboard) PD1
6: Out(to keyboard) PD3
Target microcontroller is Atmel ATMega32U2 by default but porting this project to other 8-bit AVR controllers would be easy.
Have not tested with mouse yet, but it should work somehow. I don't have an Archimedes mouse to test. Contact me if you have Archimedes mouse and can test this.
HRST FFh keyboard reset
RAK1 FEh response in reset protocol
RAK2 FDh response in reset protocol
RQMP 22h request for mouse data
PRST 21h do nothing
RQID 20h request keyboard ID
LEDS 0000 0xxx Set LED state
||`--- Caps Lock
|`---- Num Lock
`----- Scroll Lock
RQPD 0100 xxxx request to echo data. keyboard replies with PDAT.
````--- Data
BACK 3Fh ack for first byte
NACK 30h disable key and mouse
SACK 31h enable key
MACK 32h enable mouse
SMAK 33h enable key and mouse
KDDA 1100 xxxx key down data comprised of two bytes
````--- Row(first byte)/Col(second byte)
KUDA 1101 xxxx key up data comprised of two bytes
````--- Row(first byte)/Col(second byte)
MDAT 0xxx xxxx
``` ````--- X(first byte)/Y(second byte)
mouse data
Keyboard sends HRST to System when it powers up and detects user reset or error.
Also keyboard reply with HRST to HRST command from system.
Reset sequence:
System Keyboard
------------------------------------------------------
sends HRST
sends HRST(as reply)
sends RAK1
sends RAK1(as reply)
sends RAK2
sends RAK2(as reply)
sends SMAK/SACK/MACK
no reply for last ack
The protocol is essentially half duplex, so in normal operation the keyboard controller will not send a second byte until it has received BACK.
Keyboard sends code for key event with command KDDA(key down) or KUDA(key up).
Key data comprised of two bytes, byte1 encodes Row and byte2 does Col.
Scan code = (Row << 4) | Col
Key matrix:
| R/C | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | ESC | F1 | F2 | F3 | F4 | F5 | F6 | F7 | F8 | F9 | F10 | F11 | F12 | Prt | ScL | Brk |
| 1 | `~ | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 | -_ | =+ | £ | BS | Ins |
| 2 | Hom | PgU | NmL | P/ | P* | P# | Tab | Q | W | E | R | T | Y | U | I | O |
| 3 | P | [{ | ]} | | | Del | Cpy | PgD | P7 | P8 | P9 | - | LCt | A | S | D | F |
| 4 | G | H | J | K | L | ;: | '" | Rtn | P4 | P5 | P6 | P+ | LSh | Z | X | |
| 5 | C | V | B | N | M | ,< | .> | /? | RSh | Up | P1 | P2 | P3 | Cap | LAl | Spc |
| 6 | Ral | RCt | Lef | Dow | Rig | P0 | P. | PEn | ||||||||
| 7 | SW1 | SW2 | SW3 |
SW*: mouse button
Keyboard sends two mouse movement data for X and Y with command MDAT at once.
First command encodes 7-bit X counts and sencond does 7-bit Y counts(-64 to 63).
31250 baud, 8-bit data(LSB-first), non-parity, active low
Format: start bit(0), 8-bit data(LSB first), stop bit(1)
0 ___ ___ ___ ___ ___ ___ ___ ___ ___
1 ___/ \___X___X___X___X___X___X___X___\______
S 0 1 2 3 4 5 6 7 S
For example,
0 ___
1 ___/ \______________________________________ HRST(FFh)
S 0 1 2 3 4 5 6 7 S
0 ___ _______ _______
1 ___/ \_______/ \_______/ \______ SMAK(33h)
S 0 1 2 3 4 5 6 7 S
pulse width: 32us = 1sec / 31250
- Reset sequence:https://i.imgur.com/hbDONtf.png
- Key down:https://i.imgur.com/Iag9AXD.png
- Key up:https://i.imgur.com/6UPmcMe.png
Mini-DIN-6P female socket from the front:
,--_--. 1: Reset
/ o6 5o \ 2: NC
| o4 3o | 3: GND
- 2o o1 - 4: 5V
`-___-' 5: In(from keyboard)
6: Out(to keyboard)
Reset pin is pulled down when reset button on keyboard is pressed by user.
Keyboard microcontroller is also restarted when the button is pressed and Reset sequence begins again.
Notice that this pin is given 12V on system according to schematics. A300 Keytronic keyboard is not connected to the pin.
9-pin Mini DIN(not interchangeable with Microsoft bus mouse)
______
/________\
/ o9o8 o7 \
| o6 o5 o4 o3|
| o2 o1 |
`------'
Pin number Pin function
6 5v supply for Mouse
4 0v return for Mouse
2 Switch 1
3 Switch 2
8 Switch 3
1 X Reference
5 X Direction
7 Y Reference
9 Y Direction
Rise and fall time 20 maximum, Vol to Voh or Voh to Vol. Each mouse switch operates with a contact closure to 0 V. The switch debounce period is 20 ms minimum.
Confirmed that SW1/2/3 on A300 keyboard with TMK converter. Proper key data appeared when the pins were pulled down with 1K ohm resistor. 2023-10-25
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Acorn Manuals https://chrisacorns.computinghistory.org.uk/docs/Acorn/Manuals/Manuals.html
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Bitsavers https://bitsavers.org/pdf/acorn/
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Photos https://imgur.com/a/1DNHK9C
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Archimedes to PS/2 adapter https://stardot.org.uk/forums/viewtopic.php?t=9334