Author: ELECTRONOOBS
20/11/2018
This is my new boar for a smartwatch project. Please see the other version on this post in order to compare the final results. First of all, the shape. I realised that giving the space for a watch belt would be a big advantage. Now, once the board is finished, I can put a small plastic 3D printed case, but put the belt on the holes that are specially made for a watch belt. The holes are actually vias with a 20mm width. Let's talk about the rest of the board. Well, now, this new version has a FTDI programmer, so we could program it directly with a USB connection instead of using an external FTDI module conected to the UART pins. The used chip is a CH340 that is connected to the RX and TX pins of the ATmega chip. Also, as you can see the ATmega328 chip is very small and now, it's on the top layer of the PCB.

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In the middle we have the i2c pins for the OLED display. It will be a display of 128 by 64 pixels. On the left side we have the UART pins for the Bluetooth module that will make the connection to an Android smartphone. A good idea, was to put a voltage divider that will lower the battery voltage below 1.1V. The ATmega chip has an internal voltage reggerence of 1.1V. And with that voltage divider we could measure the battery level and know when to charge the watch.
And that's the next thing. The board has a LiPo charging circuit that will charge the 3.7V battery using the USB connector, just as any other smartwatch. We can see the pads for 2 LEDs below the screen, those LEDs are used to show when the battery is full and when it is charging using red and blue colours.

On the right side, we have 3 x 90º push buttons used to activate the screen, scroll through the menu, set time and more. On the bottom right corner we have SPI pads in case the ATmega chip dose not have a Bootloader and we have to upload one using the SPI connection. On the back, this new version has space for a very small buzzer so this watch could also have an alarm. That's wuite nice right? So that's it. What do you thing of the new design?

Can't wait to solder and program this new board. Stay tuned for more...