Questions about "dumb watch" project

[tastewar]

I have begun work on a watch project, but it is not a connected watch. I'm just using the TinyScreen for the display. I'm planning to have a TinyDuino, the RTC board, and the display. I guess my questions revolve around battery life, as I'd like to have it powered by the coin cell, and last a long time. In my plan, the display remains powered off until the user presses a button to have the time displayed. Here are a few questions for starters:

• Will those three boards fit just fine in the watch case?
• Can a button on the screen trigger an interrupt so the CPU can sleep?

I'm guessing that if the answer to 2 is no, I'm pretty much sunk already. And if that's so, I'd suggest that it might be nice for a future rev of the board to have one of those buttons available that way, perhaps by cutting a trace and soldering a jumper. Anyway, if I can't use the coin cell, I guess I can use the lithium battery, but that means having to also include the USB board for charging, and makes maintenance a hassle, unless *4* boards plus battery fit in the 3D printed case.

Any other thoughts/advice?

[Ben Rose]

Not sure if you've tested it, but I can guess the coin cell plus OLED will cause some problems- OLED plus microcontroller pull about 30-60+ mA depending on brightness, so the coin cell voltage may sag to brownout levels pretty quickly.

1. The case definitely only holds 3 boards plus battery. Big compromise, but you can (maybe)imagine it even taller- cubewatch.
2. Bit of a coincidence- I'm testing the first production run of Rev5 TinyScreen boards that address these issues. I fixed a mistake with power consumption when the screen is 'off'(a few mA to a few uA), and added an optional pin 2/3 interrupt return from the GPIO board that is connected to the buttons- so with a solder bridge and library update, you can do wake on button press.

I haven't done enough testing, but I would guess our current processor board plus TS Rev5 and an RTC should be able to last at least a month on our standard rechargeable lithium battery, depending on screen usage- I think that's the way to go, does that sound doable?

[tastewar]

OMG, Ben, I just placed another order for a TinyScreen. Is there any way to ensure I get one from this production run??

[Ben Rose]

PM your email- I'll write a note if it hasn't shipped. Want the interrupt line bridged on pin 2 or 3? Then I don't have to test the software myself