Although looking a little ugly, I finally have a working IoT temperature sensor. I had put it down for a time, but returned to this project in January.
The board now:
The Rest server writes the record to a MySQL database.
This is version 1.2 of my board. Originally I attempted to get a tiny BGA part working, but in my home shop I found it difficult to assemble the board. I changed to an alternate SMT land-pattern that I've had more success with.
Initially I expected to use a DS18B20 temperature IC. I was able to implement firmware that communicated with this part, but the sensor readings were higher than I expected. I believe it was being either internally heated or possibly being effected by heat from the CPU.
I replaced the DS18B20 with a thermistor. The board was able to accomodate the thermistor in the same location as the DB18B20 and it proved to be more acurate at measuring the temperature. Should I manufacture more of these boards I will make a new revision of the board specific to the thermistor implementation, but I have 3 boards including this one that I will be able to use.
Even though it looks a bit grubby and some of the parts are not aligned this board works.