PIC16F73 with PCF8591

[Habasch]

Hello all,
a little newbe question:

Does everybody have a code example how to read data from an PCF8591 A/D converter over the i2c bus.

I have some problems with that. Always when I start reading with I2CREAD the Watchdog will reset the PIC.

Here my code:

' Switch comperator mode on all ports off
ADCON1 = %00000111


' LCD-Module settings
DEFINE LCD_DREG PORTA
DEFINE LCD_DBIT 0
DEFINE LCD_RSREG PORTA
DEFINE LCD-RSBIT 4
DEFINE LCD_EREG PORTA
DEFINE LCD_EBIT 5
DEFINE LCD_BITS 4
DEFINE LCD_LINES 4
DEFINE LCD_COMMANDUS 2000
DEFINE LCD_DATAUS 50

DEFINE I2C_HOLD 0
DEFINE I2C_SLOW 1

SCL VAR PORTC.3 ' Clock pin
SDA VAR PORTC.4 ' Data pin
SAMPLE VAR BYTE ' Holds data from slave
CONTROL VAR BYTE
DEVICE1 VAR BYTE

CONTROL = %00000000
DEVICE1 = %10010100

Pause 100 ' Wait for LCD to start up

LCDOut $fe, 1, "I2C-TEST" ' Display
Pause 1000


loop:
' DEVICE 1
LCDOut $fe, 1, "DEVICE1: "
I2CRead SDA,SCL,CONTROL,DEVICE1,SAMPLE,timeout
LCDOUT SAMPLE
Pause 500

GoTo loop


timeout:
LCDOut $fe, 1
LCDOut $fe, $80, "timed out"
Pause 1000

GoTo loop


Thanks, Habasch

[sougata]

Hi,

I am curious to know what made you decide that it is a watchdog reset. Did you debug the POR registers.

PBP drives the lines in an open collector fashion. That is it toggles between input and output. This facilitates the slave to pull down the line for acknowledge. So pull ups are absolutely necessary. Hope you have done it. A schematic post and complete code can be useful.