Hi
You only need to open each physical interface (eg. if a processor has 2 x I2C interfaces, each has to be opened individually and each then has its own handle for communication).
In you case the addressing is purely in the message itself and only one handle exists.
Here is how the time is read from a DS1307 RTC:
#define ADDRTC_READ 0xd1 // read address of DS1307
#define ADDRTC_WRITE 0xd0 // write address of DS1307
static const unsigned char ucGetTime[] = {ADDRTC_WRITE, 0};
static const unsigned char ucSlave[] = {7, (ADDRTC_READ), OWN_TASK}; // read 7 bytes from this address
fnWrite(IICPortID, (unsigned char*)ucGetTime, sizeof(ucGetTime)); // set the read address
fnRead(IICPortID, (unsigned char *)&ucSlave, 0); // start the read process of 7 byte
If you now want to read from an EEPROM it looks like this:
#define ADD_EEPROM_READ 0xa5 // read address of I2C EEPROM
#define ADD_EEPROM_WRITE 0xa4 // write address of I2C EEPROM
static const unsigned char ucSetEEPROMAddress0[] = {ADD_EEPROM_WRITE, 0};
static const unsigned char ucReadEEPROM[] = {16, ADD_EEPROM_READ, OWN_TASK};
fnWrite(IICPortID, (unsigned char *)&ucSetEEPROMAddress0, sizeof(ucSetEEPROMAddress0)); // set the EEPROM address to read
fnRead(IICPortID, (unsigned char *)&ucReadEEPROM, 0); // start the read process of 16 bytes
Notice that the handle remains the same since it is using the same physical IIC interface.
To queue reads of both devices it would look like this:
static const unsigned char ucGetTime[] = {ADDRTC_WRITE, 0};
static const unsigned char ucSlave[] = {7, (ADDRTC_READ), OWN_TASK}; // read 7 bytes from this address
static const unsigned char ucSetEEPROMAddress0[] = {ADD_EEPROM_WRITE, 0};
static const unsigned char ucReadEEPROM[] = {16, ADD_EEPROM_READ, OWN_TASK};
fnWrite(IICPortID, (unsigned char*)ucGetTime, sizeof(ucGetTime)); // set the read address
fnRead(IICPortID, (unsigned char *)&ucSlave, 0); // start the read process of 7 byte
fnWrite(IICPortID, (unsigned char *)&ucSetEEPROMAddress0, sizeof(ucSetEEPROMAddress0)); // set the EEPROM address to read
fnRead(IICPortID, (unsigned char *)&ucReadEEPROM, 0); // start the read process of 16 bytes
Notice that the input and output buffers of the IIC interface (as defined when opening) need to be adequately large to accept all data in input and output queue at the same time.
When the reads complete, the first one read will arrive first (that is, in the order that they were requested).
In your case, you need only to change the commands to suit your IIC devices: change the read/write addresses and send the correct data to prepare the read. The RTC and EEPROM are quite similar since first a write is performed to set the internal address and then the read part is started to return a certain number of bytes starting at this internal address. Most IIC devices works very similarly to this.
Regards
Mark
