The first version may be a bit of a stretch — I tried to make it as small as possible, fitting in the 5x5cm limit of PCB manufacturers, so that it will be cheap to make the PCBs. Using the cheap ST7735 TFT display, and a cheap ATSAMD21E chip. I also tried to put all the components on one side of the board, but failed with that — the power and reset switch had to go on the back, as well as the buzzer.
This Sensor Board is yet another variation of another one on my site. It is not for sale with no real purpose in mind but the design files to make your own are here. The project was created as design challenge. My full time job is pcb design work and as a hobby I enjoy experimenting with new design ideas.
This was one of the more challenging designs I’ve worked on in a while. A few times I’d given up on routing it. Evan using four routing layers I found it tough. The idea was to hide the bezel of the display behind the board but have sensor components on that same board. It would look something like a little tiny television with all the components around the edges.
This latest revision has fixed a few issues I found on previous versions but the design idea can possibly help others in some way. Full credit goes to Adafruit for publishing the Feather M0 design files along with the bootloader. I used the Feather design to create the schematic for my board.
What I’d like to give away one SAMD21 logger/sensor board to someone, wherever in the world you are. Why I’m a hardware guy, not a programmer. I’ve had fun designing this project and wrote simple code to verifying everything works. There is enough hardware and sketch space available to create a pretty cool logger project. […]
It’s pretty tiny so a 4 layer board made the whole job easier. The top and bottom are pretty much dedicated for components, layer1 are tracks and power traces, layer2 is a ground plane. Mixing up an internal plane and routing layer was interesting.
The hardware consists of:
SAMD21G18A processor (used in the Adafruit Feather)
HDC1080DMBT temperature/humidity sensor
MCP73833 LiPo battery charger
MicroSD card connector
Navigation Button and pushbutton
0.66″ mono oled display
Micro USB connector for charging and uploading new sketches
The design files and source code are available on GitHub: