' MCP23017test.bas I2C test

 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 GPUPB = &h0D ' Port B pull-up register

 SetPin 1,I2C0sda
 SetPin 2,I2C0scl
 dim integer in0=32 'encoder pins pulled high so should be reading high in detent positions, centre pin connected to ground
 dim integer in1=10 'swap the pin definitions as required to get the correct sense of rotation

setpin in0,intB,rint 'enable interrupts on both edges of both pins
setpin in1,intB,rint
rotatedright=false
rotatedleft=false
resetenc=true

 I2C open 100, 1000
 I2C WRITE MCP23017,0,2,IODIRA,0 ' set direction to output
 I2C WRITE MCP23017,0,2,IODIRB,0 ' set direction to output

do
 mcp17
loop

sub mcp17
 print "write to mcp23017"
 for i = 1 to 6
   I2C Write MCP23017,0,2,OLATA,&b10101010 '  
   I2C Write MCP23017,0,2,OLATB,&b01010101 '  
   PAUSE     1000
   I2C Write MCP23017,0,2,OLATA,&b01010101 '  
   I2C Write MCP23017,0,2,OLATB,&b10101010 '  
   PAUSE     1000
 Next i
 I2C Write MCP23017,0,2,OLATA,0 ' turn all off
 I2C Write MCP23017,0,2,OLATB,0 ' turn all off
 pause 1000
end sub

sub rint ' rotary encoder interrupt
' code: https://www.thebackshed.com/forum/ViewTopic.php?TID=10568&PID=124755#124755
' from matherp & goc
rint2:
pin0=NOT pin(in0) 'reverse sense to get positive logic
pin1=NOT pin(in1)
if pin0 then
if pin1 and not resetenc then 'in0 and in1 both active
if rotatedleft and not rotatedright then
value=fix(max(1,value-1)) ' minimum of 1
rotatedleft=false
endif
if rotatedright and not rotatedleft then
value=fix(min(maxSensor,value+1))
rotatedright=false
endif
else 'only in0 active
if resetenc and not rotatedleft then
rotatedright=true
resetenc=false
endif
endif
else
if pin1 then 'only in1 active
if resetenc and not rotatedright then
rotatedleft=true
resetenc=false
endif
else 'both off so reset
rotatedleft=false
rotatedright=false
resetenc=true
endif
endif
if pin(in0)=pin0 or pin(in1)=pin1 then goto rint2 're-enter if another change has happened almost immediately
end sub

> option list
OPTION SYSTEM I2C GP10,GP11
OPTION LCDPANEL SSD1306I2C, LANDSCAPE
OPTION RTC AUTO ENABLED
OPTION GUI CONTROLS 59
OPTION MEMORY 60160, 100608
>