Are you sure that you have genuine MCP9808 chips ? Can you read that number on the chip ?You replaced the MCP9808 with another, is that other one from the same batch from the same seller ?
Did you know that there is a bootloader which allows to use part of the Flash to store data ? With a small sketch, there might be 10 kbytes to store data.
A few notes about the schematic:There is no diode from /RESET to VCC.Do you plan to use /RESET and RX and TX to upload a sketch with a 100 nF capacitor from DTR to /RESET ?Because of that capacitor, there could be a voltage peak on the /RESET, turning the /RESET in to High Voltage programming mode. That could corrupt the bootloader.
130 ohms for the Led ? Must it really be that bright ? Can you use a extra bright led instead of extra current ?
Running with the internal oscillator might cause trouble for the baudrate and other timing based protocols.
We need to understand the meanings of the remarks made by (1) and (2) in the above address table of the EEPROM chip. What is 'device pin configuration?' Which EEPROM will have the address 0x48?
If it works, use the internal oscillator. That oscillator can be tuned with the OSCCAL register. I had soldered an ATmega8 once, using the internal oscillator, and it turned out to have the wrong timing with freezing temperatures. So I made a formula that changes OSCCAL according to the temperature
PROGMEM is to store constants in Flash memory.You can read the Arduino reference about PROGMEM and the Nick Gammon Tutorial and you know almost everything about PROGMEM.I was talking about a special bootloader that enables to write the Flash during runtime: https://hackaday.com/2015/07/03/arduinos-and-other-avrs-write-to-own-flash/. It is fun that it is possible. You have an external EEPROM, so you don't need it.
Nick Gammon wrote a nice tutorial about power: https://www.gammon.com.au/powerDid you know that 1 MHz does not need to be energy efficient? because the code takes a long time to execute. Perhaps running at 8 MHz and going into sleep after that uses less power.
Do you have any suggestions/critiques for the board layout I've posted above?
Thanks again for the insight. Do you have any suggestions/critiques for the board layout I've posted above? I'm a pure hobbyist, so I'd appreciate any advice.
1. The Battery polarity is shown wrong. It should be reversed. Also, there is no circuit designation for the Battery like E1 or B1 or something else. It would be nice to have the EMF of the Battery shown.2. I always print the voltage rating of C1/C2 in the schematic. This helps to avoid mistake when I build the board as 10 uF capacitors come at various ratings.
3. If you are using 32-pin ATmega328, then the GND pins are: 5, 3, and 21. What is in your schematic: 3*2, 21.4. If you are using 32-pin ATmega328, then the 5V pins are: 4, 16, and 18. What is in your schematic: 4*2, 18.
5. I would recommend to add micro RESET switch in parallel with C4. This will help to diagnose the board in the future (if it malfunctions for some reasons).
6. You have not given the PCB layout of your board; we could see the organization of your chips around the MCU. It is very important to have optimum orientation/organization of the chips of the board to avoid unnecessary generation of noise signals.
7. Few inconsistencies in the symbols of your schematic like: (MOSI>: it could be (MOSI)(SDA} : it could be (SDA)