SPI : Ethernet/SD shield and others SPI devices simultaneously ...

Hi,

I recently bought an Ethernet/SDcard shield for using on a new project. I'm facing a question that i couldn't find the answer.

While using the SHIELD, as it is SPI, can i use pin 53 (SPI - SS) on my arduino MEGA2560 for enabling another component (such as an SPI-EEPROM) ? I found this text inside the ArduinoEthernetShield REFERENCE :

Arduino communicates with both the W5100 and SD card using the SPI bus (through the ICSP header). This is on digital pins 11, 12, and 13 on the Duemilanove and pins 50, 51, and 52 on the Mega. On both boards, pin 10 is used to select the W5100 and pin 4 for the SD card. These pins cannot be used for general i/o. On the Mega, the hardware SS pin, 53, is not used to select either the W5100 or the SD card, but it must be kept as an output or the SPI interface won't work.

By the way, there are others questions relating the SPI features : setDataMode, setClockDivider and setBitOrder ...

Is it possible to switch these 3 features during "relat time code execution" ? I'm looking at a solution to drive "ETHERNET", "SD CARD" and my "SPI-EEPROM".

I will not use the SPI-EEPROM a lot, it is just for saving some values if some shut-down suddenly happens. On the next POWER ON, the arduino will be configured to look inside the EEPROM to take the last values saved and continues the code execution with them. So i will probably use the EEPROM 2 time/hour, not more.

Thanks !

While using the SHIELD, as it is SPI, can i use pin 53 (SPI - SS) on my arduino MEGA2560 for enabling another component (such as an SPI-EEPROM) ?

You'd have to wander through all the source code to know for sure. Me? I'd leave that pin alone.

Is it possible to switch these 3 features during "relat time code execution" ?

During what? It is possible to change the items you listed for each device, when that device is enabled.

The Arduino has a built in EEPROM. Is there some reason to use an external EEPROM?

In fact, yes there is, because the 4KB are really not sufficient for what i will be writing to it.

By the way, there is the SD card port, available on the ethernet shield ... I'm thinking about using it instead of the SPI-EEPROM.

But something is telling me that it won't be easy to use as the SPI-EEPROM would be.

I will try and have a look @ how does the SD card R/W works and can be used on PC without having to change the FileSystem.