Add a small I2C EEPROM to the meter probe PCB

[dkonigsberg]

The design of the Printalyzer was always intended to support a variety of different meter probes, and to allow iteration on the meter probe design. However, the base unit currently has no way to actually detect what specific meter probe is connected beyond the I2C responses from the sensor itself. Since different revisions of the meter probe may use the same sensor, but different enclosures (and thus have different calibration constants), this presents a problem.

Incorporating a small I2C EEPROM directly into the meter probe would add minimal cost, but would allow both meter probe identification and sensor calibration data to be stored inside the probe itself.

For this EEPROM, there are two basic options:

• Memory with a dedicated "ID" page that can contain meter probe model/revision/serial information and then be permanently locked as read-only.
• Regular memory where all of it can be overwritten, but the firmware tries really hard to make it impossible for a normal user to overwrite the "ID" information stored at the start of the memory.

There is a cost difference between these two components, so that decision is TBD for now. However, it is possible that switching between them would require no other hardware or software changes that affect normal operation.

[dkonigsberg]

Added a M24C02-D I2C EEPROM in the Rev B prototype.