MCP23017 demo

[stan cartwright]

As there isn't a demo for mcp23017.h, I thought I'd share using porta as out.
First setting the i2c address by tieing pins 15,16,17 - a0,a1,a2 hi lo. I used gcb i2c finder and it gave address as 0x40 with a0,1,2 grounded which contradicts with info but that was arduino and maybe 7bit address??
This line is important, you can't #define MCP23017_GPIOA 0
MCP23017_sendbyte( MCP23017_addr,MCP23017_GPIOA,0) ;set port a to out
The interrupt probably wrong,should be 100 Hz.
https://youtu.be/PKG3Z9pjrAU

#chip mega328p,16
#include <MCP23017.h>
#option Explicit
   #define I2C_MODE Master
   #define I2C_DATA PORTC.4
   #define I2C_CLOCK PORTC.5
   #define I2C_DISABLE_INTERRUPTS ON
   'Optionally, you can reduce the I2C timings.
   #define I2C_BIT_DELAY 0 us
   #define I2C_CLOCK_DELAY 1 us
   #define I2C_END_DELAY 0 us

#define MCP23017_addr 0x40
;#define MCP23017_IODIRA 0; make porta output
MCP23017_sendbyte (MCP23017_addr,MCP23017_IODIRA,0)
dim lmotforward,lmotor,rmotforward,rmotor,lmotval,rmotval as byte
lmotforward=1:lmotor=1:rmotforward=1:rmotor=1

;interrupt drives motors
    On Interrupt Timer1Overflow Call InterruptHandler
    ' Initialise the timer - this is required
    ' Set prescaler to 1 and then start the timer
    InitTimer1 Osc, PS_1_1
    ' Start the timer - this is required
    StartTimer 1
    'Set here to initialise but you need to set in the Interrupt routine handler
    ' Use the Timer Calc' application that is part of Mister E PIC Mutl-calc tookset to calculate the value.
    ' Ensure you set the Prescaler in the InitTimer1 shown above
    SetTimer 1, 25538
;
MCP23017_sendbyte( MCP23017_addr,MCP23017_GPIOA,0) ;set port a to out
;
do
;your code
loop
;----- end 
'This will be called when the Timer overflows
Sub InterruptHandler
  ' Set the register to 6 to give us the 10ms Interrupt.
  ' Use the Timer Calc' application that is part of Mister E PIC Mutl-calc tookset to calculate the value.
  ' Ensure you set the Prescaler in the InitTimer1 shown above
  SetTimer 1, 25538 ;reset timer
;left stepper motor
  if lmotforward=1 Then
    lmotor++
    if lmotor=9 then lmotor=1
  else
    lmotor---
    if lmotor=0 then lmotor=8
  end if
;
  select case lmotor
    case 1
    lmotval=128
    case 2
    lmotval=192
    case 3
    lmotval=64
    case 4
    lmotval=96
    case 5
    lmotval=32
    case 6
    lmotval=48
    case 7
    lmotval=16
    case 8
    lmotval=144
  End Select

;right stepper motor
  if rmotforward=1 Then
    rmotor++
    if rmotor=9 then rmotor=1
  else
    rmotor---
    if rmotor=0 then rmotor=8
  end if
;
  select case rmotor
    case 1
    rmotval=1
    case 2
    rmotval=3
    case 3
    rmotval=2
    case 4
    rmotval=6
    case 5
    rmotval=4
    case 6
    rmotval=12
    case 7
    rmotval=8
    case 8
    rmotval=9
  End Select

MCP23017_sendbyte (MCP23017_addr,MCP23017_GPIOA,lmotval+rmotval) ;sets porta to lmotval+rmotval

End Sub

[stan cartwright]

This gives 98Hz interrupt but not from the calculator..trial error

;interrupt drives motors
    ' Add the handler for the interrupt
    On Interrupt Timer0Match1 Call InterruptHandler

    Dim OCR0  AS byte alias OCR0A
    Dim TCCR0 AS  byte alias TCCR0B
    WGM01 = 1                'Timer in CTC mode - required

    ' Set the correct regsisters.  These registers give us the correct timed Interrupt.
    ' Use the TimerCalculator from MikroElectronika to obtain the correct values for these registers.
    ' When using the TimerCalculator from MikroElectronika paste the any registers with *_Bit registers
    ' Simple cut and paste from the BASIC tab

    'Timer0 Prescaler = 0; Preload = 159; Actual Interrupt Time = 10 us
    OCR0 = 19
    TCCR0 = 0x28
    TCCR0 = TCCR0 or 0x05