Parts Arrived!

A project log for Trinket Watch

A watch with an OLED display, powered by a Trinket

davishdavish 12/19/2014 at 01:364 Comments

Parts arrived from Adafruit today! Pictured is all the main components, plus a gyroscope that I accidentally included in the snapshot. After checking the pins on the RTC, it looks like it takes 5V. Well, that won't work well with the 3.3V trinket and 3.7V battery. After some research, it looks like it can work with 3.3V logic by not soldering in the two pullup resistors. Easy enough. And for the voltage input? Let's hope that when Adafruit writes that it "works best" at 5V, it actually works at all at 3.3V. Hopefully I can test the OLED tonight with an Uno, and possibly poke around with setting the RTC.


PointyOintment wrote 12/22/2014 at 09:13 point
Did you find out if the DS1307 works at 3.3 V? I'm using one for a project (not my Trinket watch, actually; that's using a software RTC) that will eventually be powered by a 3.3 V boost converter, and if I can avoid having to add a charge pump to power the RTC, that would be nice.

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davish wrote 12/22/2014 at 15:19 point
Not yet; I'm actually not able to work on the project until the 24th, which hopefully is when I'll be testing the DS1307 at 3.3V. I'll be sure to update you once I have a definitive answer, though. The actual RTC is powered by the coin cell, so it's just a matter of if the I2C works at 3.3V, which seems fine from Adafruit's Raspberry Pi tutorials with the chip.

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davish wrote 12/26/2014 at 05:09 point

So, it turns out you need 5V to power the part of the chip that does I2C. With 3.3V to the 5V pin, I'm getting a date sometime in August of last year. It doesn't seem like there's a way around it, so I'm using a step-up voltage regulator from Pololu ( Hope that helps!

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PointyOintment wrote 12/30/2014 at 09:56 point

Thanks. That's more functionality than I expected, actually. I guess I'll have to use the charge pump. My plan is to use the DS1307's own square wave output to drive the charge pump, with it being enabled/disabled by the microcontroller.

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