So, last week I spend my time finishing the board layout and ordering the boards. The boards are currently manufactured and if all goes well I will have them before Christmas. Just that you can see how the boards will look like

For some reason, KiCad only renders the boards rectangular, but thy have rounded edges and a little cutout on one side.

Some comments on the design choices I made during the layout and how they affect the project:

• Regarding the sensors, I decided to go with the DHT11. The other members of the DHT family (e.g. DHT22) are larger and will not fit in the position I intend them to go on the board, i.e. the bottom sie between the pin headers of the trinket. However, they can still be used but have to be mounted standing on the top side.
• For space constraints I decided to leave an additional temperature sensor out for the moment. There is a pin header on the board where a DS18S20 can be mounted if this is wished by the user but for the default, the temp sensor in the DHT11 will be used.
• There are two pin headers on the board, one for I2C, where an optional I2C display can be mounted and one for a serial connection to either the PC or to a wifi serial module (ESP8266) if wished. Those are the additional output devices I promised. However, software wise they might not make it to the first version I intend to have ready for the end of the contest.
• I scaled down the resistors and caps to 0805 for space constraints.

Some lessons I learned for the next rev of the board:

• The switch will be surface mount in some future version, I just did not have time to look for/order an SMD version - through hole just takes to much space on a tiny board like this.
• Same goes for the humidity/temp sensor. Maybe I will search for an SMD version of that as well.

Thats all for now. Let's cross our fingers that everything goes well and I will have the boards soon and did not make any terrible mistakes. Meanwhile I will work on the software part.