Hi
I need Project help
I have interfaced 8 toggle switches to the PCF8574 I2C Port expander using LPC2114 Controller. I have to read the only one key status at time PCF8574 interrupt pin is connected to the External interrupt pin of the micro controller. In the External interrupt service routine I am enabling the Start bit of theI2C communication. Control will jump to the I2C interrupt routine and read the status of the I/O Pins & stops the I2C. But aim facing the problem with PCF8574 interrupts According to the PCF8574 data sheet; interrupt is generated by any rising or falling edge of the port inputs in the input mode.
I/O pins are in high state, whenever press the switch it will go to low state, by releasing the pin will go to high state.
When ever I press the switch interrupt is generating in the high to low state and low to high state, beacaise of this I am reading the input pin status 0XFF (normally all pins are in high state). Whenever I press the each switch I am getting 0XFE(sw1), 0XFD(sw2), 0XFB(sw3), 0XF7(sw4), 0XEF(sw5), 0XDF(sw6), 0XBF(sw7), 0X7F(sw8) status for corresponding switch, whenever I release the switch I am getting 0xFF status for corresponding switches,
Please suggest how to solve the above problem
Regards
Chandu