'
mode 1
option autorun on
OPTION EXPLICIT
OPTION DEFAULT NONE

dim integer porta_bits,portb_bits

const mcp23017 = &h20 ' A2, A1, A0, R/W all connected to 0V
Const i2caddr=mcp23017
const IODIRA = &h00 ' Port A IO Direction register DEFAULT = I/P
const IODIRB = &h01 ' Port B IO Direction register DEFAULT = I/P
const IOCON = &h0A ' IO Expander config register - address &h0B accesses  same register
const GPIOA = &h12 ' Port A General purpose register
const GPIOB = &h13 ' Port B General Purpose register
const OLATA = &h14 ' Port A latch register
const OLATB = &h15 ' Port B latch register
const GPUPA = &h0C ' Port C pull-up register
const GPUPB = &h0D ' Port B pull-up register
'
I2C WRITE MCP23017,0,2,IODIRA,255 ' set direction to input
I2C WRITE MCP23017,0,2,IODIRB,255 ' set direction to input
I2C WRITE MCP23017,0,2,GPUPB,&hff ' set weak pullups on all
'
Font 5
CLS
'
Do

get_portb_bits
text 0,20,bin$(portb_bits,8)
text 0,60,str$(portb_bits)
Pause 100
Loop

sub get_portb_bits
I2C WRITE MCP23017,0,1,GPIOB ' set the register to read
I2C READ MCP23017,0,1,portb_bits ' read the B port
end sub

OPTION AUTORUN ON
DIM msg(2)                                     ' array used to hold the message
I2C SLAVE OPEN &H26, 0, 0, WriteD, ReadD       ' slave's address is 26 (hex)

DO                                             ' the program loops forever
 WATCHDOG 1000                                 ' this will recover from errors
LOOP

SUB ReadD ' received a message
 I2C SLAVE READ 3, msg(), recvd                ' get the message into the array
 IF msg(0) = 1 THEN ' command = 1
   IF msg(2) = 0 THEN SETPIN msg(1), OFF       ' Not configured
   ELSEIF msg(2) = 1 THEN SETPIN msg(1), AIN   ' Analog input
   ELSEIF msg(2) = 2 THEN SETPIN msg(1), DIN   ' Digital input
   ELSEIF msg(2) = 3 THEN SETPIN msg(1), FIN   ' Frequency input
   ELSEIF msg(2) = 4 THEN SETPIN msg(1), PIN   ' Period input
   ELSEIF msg(2) = 5 THEN SETPIN msg(1), CIN   ' Counting input
   ELSEIF msg(2) = 8 THEN SETPIN msg(1), DOUT  ' Digital output
   ENDIF
 ELSEIF msg(0) = 2 THEN                        ' command = 2
   PIN(msg(1)) = msg(2)                        ' set the I/O pin's output
 ELSE ' the command must be 3
   s$ = str$(pin(msg(1))) + Space$(12)         ' get the input on the I/O pin
 ENDIF
END SUB                                        ' return from the interrupt

SUB WriteD ' request from the master
 I2C SLAVE WRITE 12, s$                        ' send the last measurement
END SUB                                        ' return from the interrupt