MCP23017 16 bit expander

[chris_cb_uk]

Hi All, I struggle sometimes reading I2C datasheets correctly.  I have the 23017 working somewhat outputting, however it is not as I expected in terms of referring to a GPIO v's latch output.  Additionally I'm having issues reading in a value.

Details thus far for the outputting to the expander and it just flashes all outputs on and off alternative from A to B using the latch functions. However when I tried to address using the actual GPIOA/B using I2COut SDApin,SCLpin, expanderwrite,$09,[%11111111] the outputs do not change.

Code Select Expand

  Device = 18F4550
    Declare Xtal = 16   
    Declare LCD_DTPin = PORTB.4
    Declare LCD_RSPin = PORTB.2
    Declare LCD_ENPin = PORTB.3
    Declare LCD_Type 0
    Declare LCD_Interface 4
    Declare LCD_Lines 2
    Declare I2C_Bus_SCL On
   
   
Symbol SDApin = PORTB.0 ' Alias the SDA (Data) line
Symbol SCLpin = PORTB.1 ' Alias the SSL (Clock) line
Symbol expanderwrite = %01000000
Symbol expanderread = %01000001

I2COut SDApin,SCLpin, expanderwrite,$05,[%10111000] 'Set configuration a
I2COut SDApin,SCLpin, expanderwrite,$15,[%10111000]  'Set configuration b
I2COut SDApin,SCLpin, expanderwrite,$00, [%00000000] 'makes all gpio port A output
I2COut SDApin,SCLpin, expanderwrite,$01, [%00000000] 'makes all gpio port B output


start:

I2COut SDApin,SCLpin, expanderwrite,$0A,[%11111111]' sets all gpio A high
I2COut SDApin,SCLpin, expanderwrite,$1A,[%00000000]   'sets all gpio B Low
DelayMS 800

I2COut SDApin,SCLpin, expanderwrite,$0A,[%00000000]  'sets all gpio A Low
I2COut SDApin,SCLpin, expanderwrite,$1A,[%11111111] ' sets all gpio B high
DelayMS 900
GoTo start
Additionally when I am trying to read the port values into the pic to display simply as a binary figure on the LCD nothing happens.

Code Select Expand

       Device = 18F4550
    Declare Xtal = 16
    Declare LCD_DTPin = PORTB.4
    Declare LCD_RSPin = PORTB.2
    Declare LCD_ENPin = PORTB.3
    Declare LCD_Type 0
    Declare LCD_Interface 4
    Declare LCD_Lines 2
    Declare I2C_Bus_SCL On
   
Symbol SDApin = PORTB.0 ' Alias the SDA (Data) line
Symbol SCLpin = PORTB.1 ' Alias the SSL (Clock) line
Symbol expanderwrite = %01000000
Symbol expanderread = %01000001
Dim ouporta As Word
Dim ouportb As Word
I2COut SDApin,SCLpin, expanderwrite,$05,[%10111000] 'Set configuration a
I2COut SDApin,SCLpin, expanderwrite,$15,[%10111000] 'Set configuration b
I2COut SDApin,SCLpin, expanderwrite,$06,[%11111111] 'resistor pullup port a
I2COut SDApin,SCLpin, expanderwrite,$16,[%11111111] 'resistor pullup port b

I2COut SDApin,SCLpin, expanderwrite,$00, [%11111111] 'makes all gpio port A output
I2COut SDApin,SCLpin, expanderwrite,$01, [%11111111] 'makes all gpio port B output
 DelayMS 100
start:

I2CIn SDApin,SCLpin, expanderread,$09,[ouporta]
DelayMS 10
I2CIn SDApin,SCLpin, expanderread,$1A,[ouportb]
Print At 1,1, Bin8 ouporta
Print At 2,1, Bin8 ouportb
DelayMS 300
GoTo start
I'm aware it's probably something very minor but I've been having issues for a few hours going back and fourth checking the datasheet.

Any pointers would be well received.

Chris

[tumbleweed]

It looks like you're writing to the wrong registers.

The 23017 powers up with IOCON.BANK = 0, so that means the default register map is the one shown in tables 3-3 and 3-5

[chris_cb_uk]

Thanks Tumbleweed, I thought I had set the iocon register $05 and $15 set in binary for my ease of understanding with reference to table reference 3-6 (page21)?

[chris_cb_uk]

Oh am I right in reading table 3-5 that as the device boots into IOCON. Bank=0 I need to address the IOCON at $0A and $0B?

[tumbleweed]

Oh am I right in reading table 3-5 that as the device boots into IOCON. Bank=0 I need to address the IOCON at $0A and $0B?

Right. Since it powers up with IOCON.BANK=0 initially the register offsets in table 3-5 apply.
You only need to program IOCON once, so pick either $0A or $0B.

If you set IOCON.BANK=1 then the other register map will apply.

[chris_cb_uk]

Works perfectly now and running as 8 in and 8 output expander.  A very nice simple solution to port expansion in an I2C line.