Requirements and Goals
During work on the Suntracker 2 R4 project, the code base quickly grew and it became increasingly harder to develop for a bigger set of I/O components and functions without support of an operating system. While capacity requirements can be solved by upgrading to a larger MCU, I wondered if a SoC approach, using a Raspberry Pi or Beaglebone etc, is better suited for a central controller and communications hub device. It should have a compact design with environmental protection, have status displays, and support both external and local communication.
As the target enclosure, I selected the Takachi model SPCP131805T as the best option in size, and the acrylic top.
The schematic can be seen in the Github hardware repo (LINK).
For fitting the PCB to the enclosure frame and mounts, a DXF CAD drawing has been made to size the PCB, which I then imported into KiCad.
One of my wishes are to have a detail TFT display. Standard HDMI solutions even at 5" exceed the enclosure width, which let me compromise on a smaller SPI-based 3.5" TFT. For fast changing parameter monitoring, I added two 4-digit Segment displays. I wanted Xbee communication and GPS module support under standard Linux 'gpsd', which required to add serial ports into the design.
Finally, a basic set of touch buttons were added to control settings, which I prefer over touchscreen for simpler GUI programming, and greater reliability.
This is the first time I attempt an SMT PCB manufacturing, and to include factory assembly. I worry for mistakes, so I keep the SMT component count small for now. Most components stay THT for self-assembly, avoiding bigger loss in case of mistakes.