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wiring.md

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Key Matrix

For the main underlay, simply wire the rows and columns straight across. This uses 6 rows (R0-R5), and 7 columns (C0-C6).

Numbering the rows from top to bottom, and the columns from outward to inward (so both sides are symmetrical), the only keys that are unused on the main underlay are C6R0, C6R1, C5R5, and C6R5

Right thumb (viewed from the bottom):

   C6R0  C7R0

C7R2 C6R1 C7R1 C5R5 C6R5 C7R5

Left thumb (viewed from the bottom):

C7R0 C6R0 C7R2 C7R1 C6R1 C5R5 C7R5 C6R5

For the directional switch below the display, use columns 0-4 on row 6.

I2C Connection

From the outside of the keyboard to inside, the pins are:

GND SCL INT SDA VCC

Having GND on the outside hopefully makes it a little more likely that it has contact first before other pins when connecting/disconnecting, if it ever happens to be pulled off while powered on.

SX1509 Connections

Notes to record which wires get connected to each of the SX1509 pins:

Pull-Ups

I installed the I2C pull-up resistors on the back side of the SX1509 boards. The SX1509 have VC1 and VC2 through-holes that are connected to the 3V3 input by default (with jumpers). These through holes provide convenient locations to install the resistors, and connect them to the SDA and SCL through-holes on this board.

Left

  • 0

    • Row 0 from Main keypad
    • Row 0 from Thumb

  • 1

    • Row 1 from Main keypad
    • Row 1 from Thumb

  • 2

    • Row 2 from Main keypad
    • Row 2 from Thumb

  • 3

    • Row 3 from Main keypad

  • VC1

    • 4.7kOhm I2C SDA pull up

  • 4

    • Row 4 from Main keypad

  • 5

    • Row 5 from Main keypad
    • Row 5 from Thumb

  • 6

    • Directional switch common pin

  • 7

  • 8

    • Column 0 from Main keypad
    • Directional switch 0

  • 9

    • Column 1 from Main keypad
    • Directional switch 1

  • 10

    • Column 2 from Main keypad
    • Directional switch 2

  • 11

    • Column 3 from Main keypad
    • Directional switch 3

  • VC2

    • 4.7kOhm I2C SCL pull up

  • 12

    • Column 4 from Main keypad
    • Directional switch 4

  • 13

    • Column 5 from Main keypad
    • Column 5 from Thumb

  • 14

    • Column 6 from Main keypad
    • Column 6 from Thumb

  • 15

    • Column 7 from Thumb

Right

The right side is the same as the left, but without the directional switch.

FeatherS3

  • 10 Right SX1509 INT

  • 7 Right I2C SCL

  • 3 Right I2C SDA

  • 3 Not connected (avoided since this is a strapping pin)

  • 1 Display RST

  • 38 Left SX1509 RST

  • 33 Left SX1509 INT

  • 9 (SCL) Left I2C SCL

  • 8 (SDA) Left I2C SDA

  • 3V3.1 Left VCC

  • GND Ground

  • 3V3.2 Right VCC