PCF8951读程序

unsigned char AD_Read()
{
    unsigned char tmp;

	iic_start();
	iic_send_byte(0x90);
	if(0 == ack)
	{
	    return ERR;
	}
	iic_send_byte(0x40);
	if(0 == ack)
	{
	    return ERR;
	}
	iic_start();
	iic_send_byte(0x91);
	if(0 == ack)
	{
	    return ERR;
	}
	tmp = iic_rev_byte();

	iic_noack();
	iic_stop();

	return tmp;
}