The Expansion Boards;
4-Slot Back Plane
6-Slot Back Plane

First thing to know is bit 0 is always 1
That is the jumpers go as 7654321 for address selection and the first bit, bit 0 is always a 1

The LED Board
No Jumpers = 76543210
No Jumpers = 11111111
Address = 255
LEDS.BAS
OUT 255,I

The Centronics Printer Board
Jumpers = 7654321
Jumpters = 0000001
Address = 3 = 00000011
OUT 3,I
CENTRONICS.BAS

The Parallel Board
Jumpers = 7654321
Jumpers = 0000010
Address = 5 = 00000101
PARALLEL.BAS
OUT 5,I

The Cassette Board
Jumpers = 0000011
Address = 7 = 00000111
CASSETTE.BAS
OUT 7,I

The FDD Board
Jumpers = 765432
Jumpers = 000010
Address = 11 = 00001011
FDD.BAS

The Serial Board
Jumpers = 7654321
Jumpers = 0001000
Address = 17 = 00010001
Switches = 100 = 9600 BAUD
SERIAL.BAS
20 OUT 16,3: REM RESET 2SIO CARD
30 OUT 16,21: REM CONFIGURE CARD FOR 8 BITS, NO PARITY, 1 STOP BIT
OUT 17,I
or
PRINT "I=",I

The SPO256-AL2 Speech Board
Jumpers = 7654321
Jumpers = 01111111
Address = 127 = 01111111
OUT 127,I
SPOWORDS.BAS

SPO256-AL2-Words.doc

My 6-Slot SetUp
Left to Right = LED, empty, Serial, Speech, Cassette, Parallel

4-Slot SetUp
My spare boards = FDD, Speech, Centronics, Serial

GitHub DHansel I/O Expansion