Thermograph v2

This is a second iteration of the Thermograph project, that was a great try and showed solid prospectives but didn't get to any finished state, hence didn't succeed.

Thermograph - is a small battery-powered device that measures temperature over time and collects the data. It is implemented on ESP8266-based microcontroller using Arduino library.

Desired Specifications

Should...

• be an autonomous device with a small display and a couple of buttons for the interaction
• be capable of permanently storing some amount of data and allowing to visualize and explore stored data
• be capable of streaming data: Serial, Wi-Fi, Bluetooth(?)
• contain internal temperature sensor such that it can be used as is (without any extra wires)
• be capable of using extended temperature sensor (ideally thermocouple e.g. MAX31855)
• be designed to not being limited from adding extra sensor (e.g. light sensor)

Some thoughts

• ESP8266 would be a better choice (comparing to Atmega328P), because of embedded WiFi module
  • Final decision was on ESP8266
• The inputs are 2 (or 3) tact buttons, hence interaction is quite limited, so the UI-design should correspond to properly
  • The ESP8266 chip deep sleep opportunity dictates on using a separate button as a on/off switch, so it's going to be on/off button + 2 additional navigation buttons
• Because of the limited storage capacity (1KB for Atmega328P and 4KB 1-4MB for ESP8266 emulated in flash -> or better using LittleFS), the storing should be optimized for capacity (using data compression, e.g. zlib, uzlib, miniz?)
  • compression is not necessary but desireable
• EEPROM is susceptible for number of overwrites, storing algorithm should consider it to avoid wearing of some specific memory segments (LittleFS solves this problem out of the box)
  • LittleFS is used
• The codebase should address the power supply is limits (e.g. using deep sleeping, when possible). Possible power supply: a couple of AA or AAA batteries

Data file format

VERSION - 1 byte

TODO List: