dim integer portabits
'SETPIN gp20, gp21, I2C
'I2C OPEN 100,100

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 2
CLS
'
Do

'then when you read:
I2C WRITE MCP23017,0,1,GPIOB ' set the register to read
I2C READ MCP23017,0,1,portabits ' read the B port

text 0,20,bin$(portabits,8)
Pause 100
Loop