In a future firmware revision I would like to include a method for calibration. This could be an in-firmware calibration routine or maybe we can just read calibration data from the SD card. It depends on what would be more costly in terms of memory. I'm leaning toward reading from the SD card. If we implement reading from the SPI Flash chip, that that would be the best candidate.
From here down I'm just gong to dump various notes and ideas as they come to me. Please comment with your thoughts.
The firmware currently has one set of calibration data for all units. It's based on the millivolts measured by the ADC. These values can be found in t400.h.
These values are then used in t400.ino.
It would be great if the calibration routine could be done without additional flashing for the firmware. Maybe put a probe in boiling water and hold down a button, then put it in a ice bath and hold the button again. Then the firmware could determine the calibration data. This could be a high memory cost.
Perhaps a calibration command could be done over serial.