PIC 18F4550 and MCP23017

[artha2]

Ok I changed it to 4.7k R and correct the port direction.
could you please tell me what im doing wrong for initializing the chip? I know the default mode chip's port are all input and all the register's bit are %000000000 according to table 1-6 page 11 pf MCP23017 data sheet it means there is no pull up, inverter. am i right?
i just need to have access to those register address which they are all again at page 11 table 1-6.
and the way to do that with I2CWRITE command is following the help page of PBP which it says: I2CWRITE DataPin,ClockPin,Control,{Address,}[Value{,Value...}]{,Label}
indicate the data pin, indicate clock pin, address of specific register that i want to change (IODIRA &00) table 1-6, address of my chip, [ and value in the bracket ]
is this the correct way?

[cncmachineguy]

Table 1.6 pg 11 shows POR/RST value of IODIRA and IODIRB is %11111111. NOT %00000000. Setting the dir to 1 makes the pin an input.

Maybe you were looking at the next 2 registers? IPOLA and IPOLB?

[DaveC3]

Take a look at your I2C data format

The proper way to send data for this chip is

i2cwrite I2C_SDA, I2C_CLK,control,[Value{..value}]

In your case it should be:

I2C_SDA is PORTC.4 or as you have defined DP
I2C_CLK is PORTC.3 or as you have defined CP

The control needs to be: (assuming you have the address lines connected to zero volts)
%01000000 or $40 for write
%01000001 or $41 for read

{PicBasic actually changes the control bit.0 for you in the statement I2CWRITE and I2CREAD}

So to set a register you need two values, the registers address and the value you want it to be.

To set the IODIRA to be outputs you would send
Value 1 control code for IODIRA is $00 see table 1-3 in the data sheet
value 2 you want to make them outputs so would be $00 (just like setting TRIS in a PIC)

I2CWRITE DP, CP, $40[$00, $00] 'IODIRA is set to output

You also need to set the IOCON register
I2CWRITE DP, CP, $40[$05, %10111000] "see data sheet register 1-6 for details


So to initialize Porta as output you would program this.
I2CWRITE DP, CP, $40[$05, %10111000] "Set configuration
I2CWRITE DP, CP, $40[$00, $00] 'Make porta all outputs

Then to write to the port you would use this:
I2CWRITE DP, CP, $40[$09,$FF] '$09 is the address for GPIOA, $FF would make the porta pins high, to set them low, send values [$09, $00]

You only need to set the weak pull-ups if you are making a port(pin) an input.

Hope this helps
Dave

[artha2]

Thanks Dave,
I really appreciate your time and patient. in I2c command where it asks about the address I thought it asks about chip's physical address, but now thank to you I can fully control this chip and use it. again thanks

Artha

[DaveC3]

You are welcome, glad I could help.

Take care

Dave