I'm planning on putting space on a shield for 2 i2c EEPROM 8-pin PDIP chips, but I want to leave one of the spaces un-populated with a chip. I plan to do a test during setup() to identify whether the 2nd chip is there or not. Anybody done this / have any issues with this?
I just happen to be waiting for some boards now that will have this same setup. The I2C I/O should return an error when trying to address an absent chip, although this assumes the size (capacity) of the chips is known, not sure how general you need it to be.
Just use some functions from a I2C scanner sketch or library to see what I2C addresses generate a response. If you know what addresses are expected to be responding it should be a quick function.
http://playground.arduino.cc/Main/I2cScanner
Lefty
The I2C EEPROMs have no signature, you can't tell what kind of I2C EEPROM it is.
Erdin:
The I2C EEPROMs have no signature, you can't tell what kind of I2C EEPROM it is.
A I2C scanner is not trying to read any data from a device, just if it responds to a specific I2C address. All I2C devices are 'hardwired' to respond to a specific I2C bus address, some have pins to change what addresses they work with within a small address range. Do you have a link to your specific I2C eeprom?
The OP knows what kind of I2C device is going to be used, but wants to know if in software he can tell if it's actually installed or not.
Lefty
Yep, I'm only concerned about whether a 24LC256, 24LC512, or 24LC1025, or nothing is installed. Should work fine for drop-in-replacement FRAM i2c chips as well. I am not attempting to support just any i2c chip. Attempting a read from the last block on the 24LC1025, followed by a read from the last block of a 24LC256, followed by a read from the last block of a 24LC256 should tell me which memory chip I have and if I have a chip at all. So I think I'm good. I'll test it on a breadboard.