Neven's Electronics Page

PS/2 Mouse to Amiga Converter

NEW: License of the source code now changed to GNU GPL v3 !
current version: V1.0 (30-Jun-2001)
What is this:

This is a simple hardware converter, utilizing PIC16F84 microcontroller, that allows you to connect a standard PS/2 mouse to your Amiga mouse port. It doesn't need any software drivers in order to run, just plug the converter into your mouse port and a PS/2 mouse into converter and off you go! No modifications are needed, neither to mouse nor to Amiga. As far as Amiga is concerned, it won't even know it is not the genuine Amiga mouse that is connected to it's port.


- an Amiga (any model, any Kickstart)
- a PS/2 mouse
- this converter

Hardware description:

circuit diagram

The heart of the converter, a PIC16F84 microcontroller, does all the job. It receives serial data packets from PS/2 mouse and after conversion outputs standard Amiga H, HQ, V, VQ movement information and three mouse buttons' status to Amiga mouse port. It does not support the 4th and 5th button nor the additional scroll wheels found on some fancy PC mice. Such mice will be recognized and used as standard PS/2 mouse with only standard movement and two or three buttons.

Oscillator in the PIC chip is configured as RC type. With 27pF capacitor and 4.7kohm resistor it will oscillate at around 3.4MHz.
10kohm pull-up resistors on PS/2 CLOCK and DATA lines wouldn't be necessary if PIC PORTB pins were used for DATA and CLOCK because of PIC's internal pull-ups, but... two resistors won't take too much space, especially if you use SMD :) The only other parts are 100nF capacitor for decoupling, 9pin SUB-D socket and 6pin MiniDIN socket, and, of course, a printed circuit board, which can be made pretty small.

Circuit diagram found in this archive is also PCB layout suggestion. I'd recommend you to remove the metal plating from the front (coupling) side of the SUB-D socket, as it is not needed anyways, and you won't have to be careful not to short any pins with it when coupling the socket with Amiga mouse port plug while Amiga is on.
Of course, PIC chip must be programmed before you can use it. ps2mouse.hex is the program in IntelHex format and ps2mouse.asm is the source code. When programming the PIC, you should set oscillator type to RC, WatchDog Timer to OFF and Power-On Timer to ON. If you don't have a PIC programmer yet, there are many PIC programmer projects on Internet or Aminet (search for APIC, devpic, pickit, Epic...)

In case your mouse freezes, simply unplug the converter from Amiga mouse port and plug it in again. This will reset the mouse and the converter. It could have been made to cycle mouse power automatically, but I've found it unnecessary. I've tested it with some very cheap chinese made mice quite a lot and I use it for a long time and never once had a mouse freeze, it works perfectly.

I can't guarantee it will work with any PS/2 mouse (it should, because it's a standard, but who knows). It works fine for me.

So far I tested it on my:

A1200 KS3.0
8MB 60ns Fast RAM board with 68882 FPU and RTC
Commodore 1084S Monitor

A500 KS1.3
A501 SlowFast RAM board (connected as CHIP RAM)
external DD floppy

It was tested with some really cheap chinese made mice. No problems were experienced, so it seemed unnecessesary to include mouse reset by cycling mouse power off/on. If you find it necessary, contact me and I'll include it in the next version.

Source code for PIC16F84

; ------------------------------------- ; PS/2 Mouse to Amiga Mouse Converter ; v1.0 (30-Jun-2001) ; ------------------------------------- ; Copyright 2001 Nevenko Baričević ; This program is free software: you can redistribute it and/or modify ; it under the terms of the GNU General Public License as published by ; the Free Software Foundation, either version 3 of the License, or ; (at your option) any later version. ; This program is distributed in the hope that it will be useful, ; but WITHOUT ANY WARRANTY; without even the implied warranty of ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ; GNU General Public License for more details. ; You should have received a copy of the GNU General Public License ; along with this program. If not, see <>. ; ------------------------------------------ ; includes ; ------------------------------------------ W equ 0x00 F equ 0x01 STATUS equ 0x03 PORTA equ 0x05 PORTB equ 0x06 TRISA equ 0x05 TRISB equ 0x06 RP0 equ 0x05 Z equ 0x02 C equ 0x00 ; ------------------------------------------ list p=pic16c84 ; ---------- registers definition ----------- byte equ 0x0c ; byte to receive or send parity equ 0x0d ; parity bit is held here parcnt equ 0x0e ; counter for calculating parity roller equ 0x0f ; help for 8 data bits to byte conversion pack1 equ 0x10 ; 1st byte of mouse data packet pack2 equ 0x11 ; 2nd byte of mouse data packet pack3 equ 0x12 ; 3rd byte of mouse data packet xrot equ 0x13 ; rotation byte for H and HQ yrot equ 0x14 ; rotation byte for V and VQ delcnt equ 0x15 ; delay counter ; --------- main routine ----------- org 0 main: bsf STATUS,RP0 ; page 1 bsf TRISA,0 ; port A, bit 0 is input bsf TRISA,1 ; port A, bit 1 is input clrf TRISB ; port B is all outputs bcf STATUS,RP0 ; page 0 movlw 0xff movwf PORTB ; port B all pins to 1 movlw 0x2d ; put b'00101101' to xrot and yrot movwf xrot movwf yrot call REC ; receive byte from mouse call INHIB ; pull CLK low to inhibit furhter sending movf byte,W xorlw 0xaa ; if it's $AA mouse self test passed btfss STATUS,Z goto IERROR call REL ; release CLK (allow mouse to send) call REC ; receive byte from mouse call INHIB movf byte,W xorlw 0x00 ; mouse ID code should be $00 btfss STATUS,Z goto IERROR movlw 0xf4 ; "Enable Data Reporting" command to mouse movwf byte call NEWPAR ; get parity for $F4 call REL call DEL200 call SEND ; send command to mouse call REC ; receive acknowledge ($FA) from mouse) call INHIB movf byte,W xorlw 0xfa btfss STATUS,Z goto IERROR call REL CHK: call REC ; receive byte1 from mouse packet call INHIB movf byte,W movwf pack1 call REL call REC ; receive byte2 from mouse packet call INHIB movf byte,W movwf pack2 call REL call REC ; receive byte3 from mouse packet call INHIB movf byte,W movwf pack3 call CONV call REL goto CHK ; receive another packet ; -------------------------------------------------------- PERROR: nop RERROR: nop IERROR: bcf PORTB,7 E_LOOP: goto E_LOOP ; -------------------------------------------------------- DEL10: nop ; delay 10us return DEL200: movlw 0x32 ; delay 200us movwf delcnt DEL2: decfsz delcnt goto DEL2 return ; --------- byte receiving subroutine ------------- REC: btfsc PORTA,0 ; wait clock (start bit) goto REC RL1: btfss PORTA,0 goto RL1 call RECBIT ; receive 8 data bits call RECBIT call RECBIT call RECBIT call RECBIT call RECBIT call RECBIT call RECBIT RL2: btfsc PORTA,0 ; receive parity bit goto RL2 btfsc PORTA,1 goto RL3 bcf parity,0 RL4: btfss PORTA,0 ; receive stop bit goto RL4 STP: btfsc PORTA,0 goto STP btfss PORTA,1 goto RERROR RL8: btfss PORTA,0 goto RL8 return RL3: bsf parity,0 goto RL4 ; ---------- bit receiving subroutine ------------ RECBIT: btfsc PORTA,0 goto RECBIT movf PORTA,W movwf roller rrf roller rrf roller rrf byte RL5: btfss PORTA,0 goto RL5 return ; ---------- subroutines ----------------- INHIB: call CLKLO ; inhibit mouse sending (CLK low) call DEL200 return REL: call CLKHI ; allow mouse to send data return CLKLO: bsf STATUS,RP0 ; CLK low bcf TRISA,0 bcf STATUS,RP0 bcf PORTA,0 return CLKHI: bsf STATUS,RP0 ; CLK high bsf TRISA,0 bcf STATUS,RP0 return DATLO: bsf STATUS,RP0 ; DATA low bcf TRISA,1 bcf STATUS,RP0 bcf PORTA,1 return DATHI: bsf STATUS,RP0 ; DATA high bsf TRISA,1 bcf STATUS,RP0 return ; ------------- send to mouse -------------- SEND: call INHIB ; CLK low call DEL10 call DATLO ; DATA low call DEL10 call REL ; CLK high SL1: btfsc PORTA,0 ; wait for CLK goto SL1 call SNDBIT ; send 8 data bits SS1: btfss PORTA,0 goto SS1 SS2: btfsc PORTA,0 goto SS2 call SNDBIT SS3: btfss PORTA,0 goto SS3 SS4: btfsc PORTA,0 goto SS4 call SNDBIT SS5: btfss PORTA,0 goto SS5 SS6: btfsc PORTA,0 goto SS6 call SNDBIT SS7: btfss PORTA,0 goto SS7 SS8: btfsc PORTA,0 goto SS8 call SNDBIT SS9: btfss PORTA,0 goto SS9 SS10: btfsc PORTA,0 goto SS10 call SNDBIT SS11: btfss PORTA,0 goto SS11 SS12: btfsc PORTA,0 goto SS12 call SNDBIT SS13: btfss PORTA,0 goto SS13 SS14: btfsc PORTA,0 goto SS14 call SNDBIT SS15: btfss PORTA,0 goto SS15 SS16: btfsc PORTA,0 goto SS16 call SNDPAR ; send parity bit SS17: btfss PORTA,0 goto SS17 SS18: btfsc PORTA,0 goto SS18 call DATHI ; release bus SL4: btfss PORTA,0 goto SL4 SL5: btfsc PORTA,0 goto SL5 btfsc PORTA,1 goto RERROR SL7: btfss PORTA,0 goto SL7 SL8: btfss PORTA,1 goto SL8 return ; -------------- subroutines -------------- SNDBIT: rrf byte ; send data bit btfsc STATUS,C goto DHIGH call DATLO SL2: return DHIGH: call DATHI goto SL2 SNDPAR: btfsc parity,0 ; send parity bit goto PHIGH call DATLO SP1: return PHIGH: call DATHI goto SP1 CLCPAR: movlw 0 ; calculate parity bit movwf parcnt btfsc byte,0 incf parcnt btfsc byte,1 incf parcnt btfsc byte,2 incf parcnt btfsc byte,3 incf parcnt btfsc byte,4 incf parcnt btfsc byte,5 incf parcnt btfsc byte,6 incf parcnt btfsc byte,7 incf parcnt return NEWPAR: call CLCPAR btfss parcnt,0 goto PARONE bcf parity,0 return PARONE: bsf parity,0 return CHKPAR: call CLCPAR ; check parity movf parcnt,W andlw 0x01 movwf parcnt movf parity,W xorwf parcnt btfss STATUS,Z return call PERROR return ; --------------- conversion to Amiga format -------------- CONV: btfsc pack1,0 ; left button goto LPRESS bsf PORTB,6 CON1: btfsc pack1,1 ; right button goto RPRESS bsf PORTB,0 CON2: btfsc pack1,2 ; middle button goto MPRESS bsf PORTB,1 MOVE: movf pack2,W ; movement conversion andlw 0xff btfss STATUS,Z call MOVEX movf pack3,W andlw 0xff btfss STATUS,Z call MOVEY return LPRESS: bcf PORTB,6 goto CON1 RPRESS: bcf PORTB,0 goto CON2 MPRESS: bcf PORTB,1 goto MOVE MOVEX: btfss pack1,4 goto LEFT goto RIGHT MOVEY: btfss pack1,5 goto DOWN goto UP LEFT: call DEL200 ; send H and HQ for left movement rlf xrot btfss STATUS,C goto LH0 goto LH1 LH0: bcf xrot,0 bcf PORTB,4 goto LHQ LH1: bsf xrot,0 bsf PORTB,4 LHQ: rlf xrot btfss STATUS,C goto LHQ0 goto LHQ1 LHQ0: bcf xrot,0 bcf PORTB,2 goto LONE LHQ1: bsf xrot,0 bsf PORTB,2 LONE: decfsz pack2 goto LEFT return RIGHT: call DEL200 ; send H and HQ for right movement rrf xrot btfss STATUS,C goto RHQ0 goto RHQ1 RHQ0: bcf xrot,7 bcf PORTB,2 goto RH RHQ1: bsf xrot,7 bsf PORTB,2 RH: rrf xrot btfss STATUS,C goto RH0 goto RH1 RH0: bcf xrot,7 bcf PORTB,4 goto RONE RH1: bsf xrot,7 bsf PORTB,4 RONE: incfsz pack2 goto RIGHT return UP: call DEL200 ; send V and VQ for up movement rlf yrot btfss STATUS,C goto UV0 goto UV1 UV0: bcf yrot,0 bcf PORTB,5 goto UVQ UV1: bsf yrot,0 bsf PORTB,5 UVQ: rlf yrot btfss STATUS,C goto UVQ0 goto UVQ1 UVQ0: bcf yrot,0 bcf PORTB,3 goto UONE UVQ1: bsf yrot,0 bsf PORTB,3 UONE: incfsz pack3 goto UP return DOWN: call DEL200 ; send V and VQ for down movement rrf yrot btfss STATUS,C goto DVQ0 goto DVQ1 DVQ0: bcf yrot,7 bcf PORTB,3 goto DV DVQ1: bsf yrot,7 bsf PORTB,3 DV: rrf yrot btfss STATUS,C goto DV0 goto DV1 DV0: bcf yrot,7 bcf PORTB,5 goto DONE DV1: bsf yrot,7 bsf PORTB,5 DONE: decfsz pack3 goto DOWN return end ; --------------------------------------------------------

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