For the signal-translation form the 0-5VDC source to the standard
RS232-level (-12VDC / +12VDC) you may choose the MAX232 or an
equivalent counterpart (ICL232 ....)
CD32 Keyboard-Port level-converter TTL->RS232 RS232
Pin4 +5V -------------Pin16
Pin3 GND -------------Pin15--------------------------GND Pin7
Pin2 TxD ------------>Pin10 (---|>*-) Pin7-------->RxD Pin3
Pin6 RxD <------------Pin9 (--*<|--) Pin8<--------Txd Pin2
C1
+--)|----Pin1 +----DSR Pin6
| + (*) |
+--------Pin3 +----DCD Pin8
C2 |
+--)|----Pin4 +----DTR Pin20
| +
+--------Pin5 +----RTS Pin4
C3 (*) |
GND--|(----Pin6 +----CTS Pin5
+ (Polung!)
C4
GND--)|----Pin16 (*) some computers need these
+ handshake connections to
C5 proper working
+--|(----Pin16
| + (Polung!)
+--------Pin2
(**)
shielding-----------------------------------------| |-shielding
connect the shielding of all cables to each other - but only
connect it to only ONE interface port connector (i used the
keyboard plug).
For the condensers C1..C5 you must get 1 uF electrolyt-condesers.
If your signal-converter is kind of the xxx232A (A-type) you must
use 0.1 uF instead (for C1..C5) [source : Maxim Data Book]
Be careful with your explorations. I suggest the serial signals
are passed through directly to the PAULA chip - so they are
slightly sensitive.