# SchematicASCII schematic of the ShortcutDeck electrical design.## Block diagram``` Arduino Uno R3 - USB serial - PC (Electron app) | receives BTN:n presses | sends OLED config | I2C (SDA=A4, SCL=A5), 5V, GND | +-- 6 buttons (pull-downs) on D2..D7 | +-- TCA9548A mux, channels 0-5 | | | | | | OLED0..5, one per channel, address 0x3C```## Full schematic``` ARDUINO UNO 5V ----+-----------------> 5V rail (OLEDs, buttons, mux) GND ---+-----------------> GND rail A4 (SDA) --+-> TCA9548A.SDA A5 (SCL) --+-> TCA9548A.SCL D2 -> BTN0, pull-down -> GND D3 -> BTN1, pull-down -> GND D4 -> BTN2, pull-down -> GND D5 -> BTN3, pull-down -> GND D6 -> BTN4, pull-down -> GND D7 -> BTN5, pull-down -> GND TCA9548A: VCC GND SDA SCL from Uno SD0 SC0 <-> OLED0 (0x3C) SD1 SC1 <-> OLED1 (0x3C) SD2 SC2 <-> OLED2 (0x3C) SD3 SC3 <-> OLED3 (0x3C) SD4 SC4 <-> OLED4 (0x3C) SD5 SC5 <-> OLED5 (0x3C) All six OLEDs share VCC and GND. Each OLED's SDA and SCL connect to one TCA9548A output pair, so they can all keep the default address 0x3C.```## Netlist```Net 5V: Uno.5V -> TCA9548A.VCC, OLED0..5.VCC, BTN0..5.ANet GND: Uno.GND -> TCA9548A.GND, OLED0..5.GND -> R0..R5 (10k pull-downs) -> BTN0..5 + D2..D7Net I2C: Uno.A4 (SDA) -> TCA9548A.SDA Uno.A5 (SCL) -> TCA9548A.SCLNet channel n (n = 0..5): TCA9548A.SDn -> OLEDn.SDA TCA9548A.SCn -> OLEDn.SCLNet buttons: Uno.D2 -> R0 (to GND) + BTN0 ... one per button, D3..D7 map to BTN1..BTN5```## NotesPull-ups. The TCA9548A breakout has onboard 4.7k ohm pull-ups on SDA and SCL.If you use a bare mux chip, add your own. Each OLED branch adds none, so onlythe main bus carries pull-ups.Polarity. Some OLED modules run on 3.3V only. If yours is 5V tolerant it workson the Uno. Most SSD1306 breakout boards accept 3.3V to 5V.Addresses. The mux sits at 0x70 with A0, A1, and A2 all low. The OLEDs all sitat 0x3C.Reset. If your OLED has an RST pin, tie it high (5V) or leave it unconnectedwhen the module does not use it.