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Page 10 - Buttons

The OSWatch uses 4 buttons for interaction. 1 for selection, 1 to cancel / go back, and 2 for up and down. (or something similar depending on each app configuration) 3 of these buttons use internal chip based pull up resistors (less hardware is better) but one uses an external pull down resistor. This fourth one is also attached to an interrupt pin, allowing this button to wake the watch up if it goes to sleep. This combined with the BLE112 wake up logic will enable the sleep mode of the watch to be low powered, only to be woken up via a Bluetooth message or user input.

The placement of my watches are for left handed ppl. The up / down on the right side are pressed using an index and middle finger, while the back / selection buttons are pressed with the thumb. The selection button (the lower one) is on an interrupt. You may want to invert these if you are right handed.

The button Schematic:

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1.) Connect Frame with Base

before you add the buttons, you need to place the completed logic frame into the base. You may need to tuck some wires out of the way. The goal here is to make the logic frame lie as flush as possible in the base. Ideally, the logic frame is 100% level with the top edge of the base. This will let you use the 4 button holes as guides for button placement.

Placing the frame

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2.) Trim buttons and place

The tactile buttons have 4 leads, connecting 2 sets of pins flowing north and south to east and west. Trim off 2 bottom leads. We only need one electrical join. Once you have 4 buttons prepped, bend the other 2 leads up slightly. Now align each one to sit properly in the button hole in the watch base. now apply a drop or two of glue to secure it in place. Repeat for all 4.

Attaching Buttons

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Let them dry, and slide the frame out. Now use more superglue to reinforce the buttons in place. Be careful not to let glue get into the mechanical part of the button. Let these fully dry.

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Be careful not to overuse glue on the buttons. You can get them stuck!

Buttons attached

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3.) Wire up the buttons

For 3 buttons, we had set aside 2 ground leads in each gap earlier. Now connect 3 of the buttons to ground on one end. On those 3, run the other end to digital pins 14, 15 & 16. For the fourth button, place the resistor in the gap, and connect one end to the ground lead on another button. The other end of the resistor goes to a lead on the 4th button. That same lead also goes to Microduino digital pin 6. finally, the opposite button lead connects to the 3V3 regulated power.

Completed circuit

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You can test these by connecting the Microduino to the FTDI setup, and running the base program. You should see trace statements on the serial monitor showing text when each button changes state (down or up)

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