Thanks for your suggestions and ideas.
SuperCAP instead of Battery for RTC so it never needs replacing.
I am not too worried about it: the DS1307 RTC consumes very little current in backup mode, and a CR1220 single battery should last for at least 5-7 years.
A more powerful 5v supply (2A perhaps) and a set of headers available for 5v out, can then solder jumper wire with a barrel plug onto it and have it power a small usb hub.. this will help people with powerful wifi usb chips and/or those who want to connect several usb devices without any reliability/stability issues.
Sure. The LM2596 switching regulator adopted in the current design can actually output up to 3A current, but a more careful design, including PCB traces and component selection, should be used if you want to reach that limit.
Header for a TPM36 Temperature Sensor on the board; mebe included so we can monitor system temperature if installed in a Greenhouse etc.
OK, good point.
A PTC Fuse instead.
There are actually two fuses on board currently, one fact-acting 2A fuse on the 24V AC line, and one 1A PTC fuse on the 5V line.
Signal Converter so we can plug some analogue sensors in and not worry about the input voltage.
Good point.
Circuitry to cutoff the external 5v rail to the Microcontroller if its powered externally/usb so people can troubleshot bad power supplies.
A SMD switch can be used for this and it should be pretty easy to add to 1.4.
AC in with Ground, Microcontroller ground tied in so any ESD coming in the sprinkler control lines does not try to go out ethernet/usb, also help cut down on RF interference.. my Elk power supply has a ground it’d be nice to use.
This would probably require a sprinkler transformer that has a ground wire. Many transformers I’ve seen use 2-prong plug and the output is 2 wires too. I’ve seen one or two transformers that have three wires (I think RainBird has one). But they are relatively uncommon.
I also want to add a few serial ports for AtlasScientic Sensor stamps: https://www.atlas-scientific.com/embedded.html but this is more for my own project where I am attempting to maintain PH and TDS automatically and getting it all into the footprint might mean I sacrifice some other circuitry.. but this could also be done with a via USB conveniently if I can power a hub from the board. (Bluetooth or FT232)
This is a little beyond my plan, so I will leave it to you to add these extra functionality 🙂