SHT40-AD1B temperature and Humidity sensor issue

[andrew007]

[Gordon23]

Hi,

I know this is an old topic, but i came across it, and was a bit confused.

The device in quetion has a 7 bit address followed by a direction bit.

I understand that the PIC uses 8 bits and in order to talk to the device the address needs to be shifted.

But - in the code suggested:-

#define SHT40_BASE_ADDR 0x88
#define SHT4X_CMD_MEASURE_HPM 0xFD

//================================
void main(void)
{
unsigned int8 wData[1] = SHT4X_CMD_MEASURE_HPM;
unsigned int8 rData[6] = {0};

ack = i2c_transfer_out(SHT40_BASE_ADDR, wData, 1);
.
.
.

ack=i2c_transfer_in(SHT40_BASE_ADDR, rData, 6);
.
.
.

while(TRUE)
{
//TODO: User Code
}
}



How would the device know if it is a read or write? The address being sent for transfer in/out is the same?

Can someone explain for me?

Thanks

[Ttelmah]

It's hidden from you when using i2C_transfer.
In these commands the read bit is automatically set for address for the
restart the 'in' command.
Normally (if you use the manual commands instead), you have to set the
read bit for a read command yourself.