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Mouse convertion from Amiga to Atari ST

To use an Amiga Mouse in the Atari ST we have to Swap Pin 1 with Pin 4.

First of all, both Amiga and Atari ST have a DB9 connector with 9 pins:

If you look at the DB9 connector, you have:
from right to left on top:
pin 1,2,3,4,5
from right to left bottom:
6,7,8,9
In the Atari the numbers are opposite horizontally

Amiga or Atari ST mouse DB9 connector

Atari ST computer port, see that is horizontally opposite

I used an old Amiga “tank” mouse, when you open it, it’s like this:

in next picture, below the wires there are numbers from 1 to 9 from right to left (you cannot see in the photo).But, those numbers are not the pins from DB9 mouse connecter. I think some mouses
have a direct relation from DB9 connector to the pins in the mouse circuit. This mouse is not
that case. In the DB9 connector, pin 1 has the (the brown cable), and in the circuit, the brown cable connects
to pin 3. So you need to know what pins in the connector correspond to what pins in the circuit.

To know witch pin in the connector corresponds to pin in circuit, i used a lamp with small PSU,
just to know where the electricity goes. (I didn't had a multimeter that time...)
just put one wire (yellow, in this case) of the lamp in a pin of DB9 connector and check witch pin will light the lamp in the circuit.

notice that some wires are cut, it was for tests ... nevermind...

As example, see that pin 2 of DB9 connector corresponds to pin 7 in circuit.

I used this PSU to give power to the lamp, but you can use a lot of different stuff, including a multimeter.

So, In the Amiga “tank” mouse the DB9 the relation is like this:

DB9 connector - pin in circuit:

pin 1 in DB9 connector is Pin 3 (brown wire) in mouse circuit
pin 2 in DB9 connector is Pin 7 (red wire) in mouse circuit
pin 3 in DB9 connector is Pin 4 (orange wire) in mouse circuit
pin 4 in DB9 connector is Pin 6 (yellow wire) in mouse circuit
pin 5 in DB9 connector is empty, it does not have a wire
pin 6 in DB9 connector is Pin 2 (blue wire) in mouse circuit
pin 7 in DB9 connector is Pin 9 (grey wire) in mouse circuit
pin 8 in DB9 connector is Pin 5 (white wire) in mouse circuit
pin 9 in DB9 connector is Pin 1 (black wire) in mouse circuit

To do an Atari mouse all we have to do is swap pin 1 with 4, in the DB9 connector not the circuit,
so,
DB9 pin 1 is pin 3 in circuit and
DB9 pin 4 is pin 6 in circuit

Just swap wires in circuit pin 3 with 6 or you can do a DB9 converter, and in that case you have to swap pin 1 with 4 in the DB9, it all depends where you want to work.

Just in case you need to know what each pin do:

Pin Atari Amiga
1 XB YA (V-pulse)
2 XA XA (H-pulse)
3 YA YB (VQ-pulse)
4 YB XB (HQ-pulse)
5 NC MBUT
6 LBUT LBUT
7 +5V +5V
8 GND GND
9 RBUT RBUT

5 NC is supposed to be middle button in Amiga, but in this case, the “tank” mouse does
not have any wire in DB9 pin 9