Can a DS1307 be added to the OEM BASIC Stamp 2sx SDA/SCL lines?

Sens-a-Dat

I am testing the design of the OEM BASIC Stamp 2sx to further my education.

My question today is whether I can add a DS1307, i.e. an I2C Real Time Clock, to the same SDA and SCL lines which go to the external EEPROM containing the program? I realize the Slave Addresses for the EEPROM and DS1307 are different, but I do not know whether the Interpreter program within the SX28 will permit a second I2C device on the same SDA/SCL lines for the external program chip.

Thank you for your help.

Gary

Mike Green

No, you cannot.· The user's Basic program cannot access the I2C bus containing the program EEPROM.· If you do attach the DS1307 to those lines, it will be ignored.

Bruce Bates

Gary -

For my money whether it will work, or whether it won't is rather moot, since it will rather obviously void the warranty. I'm also not sure how kindly Parallax would take to altering their proprietary product. If there is a performance impact in doing it, I'm sure they wouldn't be too happy about. Here's what I mean.

You may want to consider this. If there is contention on the data line from two I2C devices, I suppose it's possible that one I2C process may end up waiting on another I2C process, and thus slowing things down. This is particularly true and possible for EEPROM memory WRITES. One needs to WAIT for a memory write to complete, before continuing, to ensure the write was successful. It's certainly possible to wait before the write to eat up time, but that leaves the one process at the possible mercy of the other. I've no idea whether the PBASIC Interpreter waits before or after the write, or if it even matters.

If you'd like some other reasons NOT to do it, I suspect others may chime in.

Regards,

Bruce Bates

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
There is no pleasure in having nothing to do;
the fun is in having lots to do, and not doing it!