MCP23016 Babbles addresses other than 001

[Jerry R]

Hello:

This one has kept me up a week of nights.

Using a PIC18F452 with three MCP23016 port expanders. Using hardware I2C ports SCLK (RC3) and SDA (RC4). Pull-ups on both line to +5V. Only three MCP23016 on bus, nothing else. Have three MCP23016 hardwired so that their addresses are 000b 001b and 010b.

I only write to the expanders no read requirement

Using v3.249 PCWH to compile and ICS-40U debugger

Code is shown below

Addressing device 000b works fine. However, addressing either 001b or 010b devices results in no initialization and, of course, no output. The outputs of the expanders are floating around 3.5 volts after writing 0x00 to them.

I examine the I2C bus to reveal a considerable amount of babbling going on as I try and initialize either the 001b or 010b device. I have some nice logic analyser pictures if anyone is interested. Both clock and SDA lines are toggling wildly as I attempt to initialize either the 001b or 010b device.

I'm at a loss. Any help would be much appreciated!

Regards

#include <18F452.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP,PUT
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7,ERRORS,stream=PC)
#use i2c(master,sda=PIN_C4,scl=PIN_C3,FORCE_HW)

//For I2C Port Expanders

// COMMAND BYTE
#define GP0 0x00
#define GP1 0x01
#define OLAT0 0x02
#define OLAT1 0x03
#define IPOL0 0x04
#define IPOL1 0x05
#define IODIR0 0x06
#define IODIR1 0x07
#define INTCAP0 0x08
#define INTCAP1 0x09
#define IOCON0 0x0A
#define IOCON1 0x0B


//MCP23016 I2C Routines

void write_to_MCP(unsigned char WriteAddress, unsigned char cmdByte,
unsigned char Data)
{
i2c_start();
delay_us(20);
i2c_write(WriteAddress);
delay_us(20);
i2c_write(cmdByte);
delay_us(20);
i2c_write(Data);
delay_us(20);
i2c_stop();
delay_us(50);
}



void init_mcp23016(unsigned char MCP23016_Device_Address)
{

// Set-up selected I/O expander unit

write_to_MCP(MCP23016_Device_Address, IPOL0, 0x00);
write_to_MCP(MCP23016_Device_Address, IPOL1, 0x00);

write_to_MCP(MCP23016_Device_Address, OLAT0, 0x00);
write_to_MCP(MCP23016_Device_Address, OLAT1, 0x00);

write_to_MCP(MCP23016_Device_Address, IODIR0, 0x00);
write_to_MCP(MCP23016_Device_Address, IODIR1, 0x00);
}
//==============================================================================

//=====================CALLING ROUTINE TO INITIALIZE
Init_All_Outputs()
{
ADR0_GP0= 0X00;
ADR0_GP1= 0X00;

init_mcp23016(0x40);
write_to_MCP(0x40, OLAT0, ADR0_GP0);
write_to_MCP(0x40, OLAT1, ADR0_GP1);
Delay_ms(10);

init_mcp23016(0x42);
write_to_MCP(0x42, OLAT0, ADR1_GP0);
write_to_MCP(0x42, OLAT1, ADR1_GP1);
Delay_ms(10);
}

[/img]

[PCM programmer]

All examples in the data sheet show two data bytes. The order is:

[Jerry R]

PCM Programmer: Thanks for your reply. A wake-up call regarding using other's code without fully understanding it. I took this afternoon/evening to re-write the entire routines, understanding each step and PRESTO!

Thanks for the slap!
Regards