P3V3 Revision 2 - Suggestions for additional features

I am in the process of revising the P3V3 development board for the next manufacturing run. The new revision will have the same board size and header positions, but will add an additional pin to the top right that will break out the VDDA pin. The board layout has been optimized and there is some additional space on the board. I would like suggestions on placing pads for some optional features. Here are some of my thoughts. The board will be available with and without the optional components.

  • VIN voltage monitoring circuit. This would enable you to monitor the voltage of the power supply or battery that is powering the board. Requires two Imp pins. (A & D).
  • Analog temperature sensor
  • I2C temperature & humidity sensor. C3V0 will have the Si7021 as an option.
  • Light sensor

This is somewhat minor, but when I have used the C3V0 i have enclosed them in a case with the battery, the cover having 4 screws.

Removing 4 screws for blinkup is fine (rare) but rebooting the device (disconnecting battery power) required removing the case cover and unplugging the battery.

I found myself wishing for a set of pads for a power switch, such that i could solder two leads between switch and imp board, mount switch on case exterior, then assemble it all and have full reboot ability, without removing cover.

I know I could have wired this up in minutes, but I never really did, and I guess I’m thinking more about future versions of my test rigs, and convenience.

Thanks, I’ve spent some time thinking about the same thing. C3V0 is getting a battery monitor circuit as a standard feature, and pads for an Si7021 Temp/Humidity sensor as well as a Pin 1 wakeup switch as optional features.

As far as Blink-Up is concerned, I’d recommend drilling holes in the enclosures and wiring through hole components… this is really easy with the solder jumpers.

A switch on C3V0 is a little more complicated. Do you switch at VIN (before the charging chip), or after it. (Before the regulator). If you switch at VIN, the battery is still powering the circuit. But if you switch after it, at VSYS, the battery is still powering anything else in the circuit. It really comes down to each project.

I really like the tiny rocker switches from Cherry that I have posted on the store. They are easy to install and use, and I haven’t found a smaller size so far.

A board mounted On/Off switch on P3V3 might work ok. There aren’t many small surface mount slide switches available, and they aren’t cheap, but here is a possibility, if it would fit on the board. It could be mounted on the bottom of the PCB, but that might be awkward.


Scratch that… its not fitting on the board top.

Sometimes I pull the VIN/USB jumper (on the P3V3) when I need to cycle power. I haven’t looked to see how this relates to the C3V0.

I wonder if there’s room for a solder “through hole” at each of the jumper pins in order to connect a wire and use an external switch if desired with the jumper removed? Obviously, this is like the solder pad @solarishot suggested, but may be easier to connect to.

Another option I’ve used is to get some female breadboard jumper wires, pull the jumper from the USB/VIN jumper pins and then connect the female jumper wires to the pins to connect to an external device, such as a switch. The female jumpers can be found at Radio Shack stores.

Yep, the power selector switch is the place to switch power on the P3V3… its pretty easy to remove the header if you purchased it that way. It would be really cool to have a switch mounted on the board edge, but I haven’t found anything that isn’t either size or cost prohibitive.

I’m swapping some things around to add more power switching options on C3V0.