Hello,

Thanks for your comment and your support!
I'm not a C-code expert, I am just a beginner.
At this moment I'm not interessed in the mixed mode of the PCF8574 (I/O-Expander)
I use only 8 inputs switches. There are NO output leds on this PCF8574.
So, your code seems rather complex for a simple -read 8 input- instruction.
Maybe, it is necessary!
But is it possible to write the C-code without FUNCTIONS?

Best wishes

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Hello!

You must set the port bit before reading.

Eg:

If the PCF has an entry on this bit and bit 0 is pull up, you must define one. Or better WRITE 1 to this bit.

But if you do not set to 1 and the pin is low, the read will return 0.

The PCF is free direction control, refer to this datasheet:
"The device has a quasi-bidirectional I / O port 8 bits (P0-P7), including latched outputs capable of handling high current for driving LEDs directly. Almost Each bidirectional I / O can be used as an input or exit without the use of a steering control signal data. "

See data sheet for additional information:
http://www.ti.com/lit/ds/symlink/pcf8574.pdf

Look for a good VSM simulator, for testing without damaging components, so you can test the code and then submit to the board real.

Try this code bellow,

Good luck!

// ----------------- Begin Code

//Declarations section
const PCF_Addr0 = 0B01000000; // 0 1 0 0 A2 A1 A0 R/W - 1 PCF
const PCF_Addr1 = 0B01000010; // 0 1 0 0 A2 A1 A0 R/W - 2 PCF
const PCF_Addr3 = 0B01000100; // 0 1 0 0 A2 A1 A0 R/W - 3 PCF

// Software I2C connections
sbit Soft_I2C_Scl at RC3_bit;
sbit Soft_I2C_Sda at RC4_bit;
sbit Soft_I2C_Scl_Direction at TRISC3_bit;
sbit Soft_I2C_Sda_Direction at TRISC4_bit;
// End Software I2C connections

int WrPCF(int addr, int Data)
{
int ack1;
Soft_I2C_Start();
Soft_I2C_Write(addr);
ack1 = Soft_I2C_Write(Data); // return ACK for check
Soft_I2C_Stop();

return ack1;
}

int RdPCF(int addr)
{
int rd_data;
addr = addr | 1; // r/w=1
Soft_I2C_Start();
Soft_I2C_Write(addr);
rd_data = Soft_I2C_Read(0);
Soft_I2C_Stop();

return rd_data;
}


void main() {
TRISA = 0;
TRISB = 0;
TRISC = 0;
TRISD = 0;
TRISE = 0;

Soft_I2C_Init();

delay_ms(500);

while (1)
{
WrPCF(PCF_Addr0, 0B10111001);
//______________________|||||||^ - this bit (0) with button switch to low
//______________________|||||||--- this bit(s) (1 up to 7) with led enable high
delay_ms(500);

PORTB = RdPCF(PCF_Addr0); // PORTB is 10111001 or 10111000

delay_ms(500);

WrPCF(PCF_Addr0, 0B00000001);
//______________________|||||||^ - this bit (0) with button switch to low
//______________________|||||||--- this bit(s) (1 up to 7) with led enable high
delay_ms(500);

PORTB = RdPCF(PCF_Addr0); // PORTB is 00000001 or 00000000

delay_ms(500);

}
}

// ----------------- End Code

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