For some time I have been thinking of building a general purpose board. The idea came out of a discussion about a security monitoring device. Since the I have come up with several additional applications for a very similar unit.

It may now be time to combine the requirements and see if I can fit it into the originally chosen enclosure without making it more complex or expensive.

Required Features:

• several analog and digital inputs
• a couple of outputs
• a couple of status indicators
• low power design
• internal battery (2x 18650 cells)
• wide supply range – 5 to 35V DC
• comms: GSM and wifi
• readily accessible programming/serial port
• USB OTG connector
• I/O expansion connector

Notes:

• few I/O to keep it small and simple
• ** 6. can be solar powered
• ** 7. wifi module simpler than ethernet
• ** 9. USB OTG allows peripheral connection (ie. web-cam)
• **10. I/O exp, allows application specific I/O
• I already have an enclosure in mind which dictates the board size, shape and connector layout, therefore the hardware features that can be included. The enclosure is quite small, which will prevent feature creep.
• Low power design allows the CPU to shut down hardware when not needed. Power supply design for low quiescent draw and power down.
• Internal battery, charged when external power applied. Battery allows solar power for remote applications. Connector allows external battery capacity increase.

.