Custom PCB Design for Calculator

flux

I’m blocked before I can modify the project because execution credits are unavailable right now, so I cannot add components or generate the live schematic in Flux yet.
Current project state:
  • Empty project
  • 0 components
  • 0 nets
  • No schematic changes have been made
What remains to be done when execution is available:
  1. Rename/document the project for the calculator replacement PCB.
  2. Add the ESP32 NodeMCU DevKit V1 CP2102 module.
  3. Add the SSD1306 I2C OLED connector/module.
  4. Add 50 tactile switches arranged as a GPIO-efficient keyboard matrix.
  5. Use an 8-row x 7-column matrix, supporting up to 56 keys with only 15 GPIOs.
  6. Avoid ESP32 boot strapping pins GPIO0, GPIO2, GPIO12, and GPIO15 for keyboard scan lines.
  7. Connect OLED I2C:
    • SDA → GPIO21
    • SCL → GPIO22
    • 4.7 kΩ pull-up from SDA to 3.3 V
    • 4.7 kΩ pull-up from SCL to 3.3 V
  8. Connect OLED VCC to ESP32 3.3 V.
  9. Tie ESP32 GND, OLED GND, and keyboard matrix reference ground/common return together.
  10. Add schematic documentation for firmware pin mapping and key positions.
  11. Run schematic review/ERC before moving to layout.
Recommended GPIO mapping for the next pass:
  • Matrix rows: GPIO13, GPIO14, GPIO16, GPIO17, GPIO18, GPIO19, GPIO23, GPIO25
  • Matrix columns: GPIO26, GPIO27, GPIO32, GPIO33, GPIO34, GPIO35, GPIO36
  • I2C OLED:
    • SDA: GPIO21
    • SCL: GPIO22
Important note: GPIO34, GPIO35, and GPIO36 are input-only pins on ESP32, so they are suitable for matrix column inputs, not row outputs. The firmware should scan rows as outputs and columns as inputs with pull-ups/pull-downs handled carefully; external pull resistors may be needed on input-only pins depending on the DevKit/module behavior.
For debouncing: I recommend firmware debouncing first, not one capacitor per key. A 50-key matrix with per-key capacitors can slow scanning and cause ghosting-like behavior. If reliable multi-key detection is needed, add one diode per switch; otherwise, firmware debounce is simpler and better for a calculator-style keypad.
Add key diodes
Map all keys
Find ESP32 part
Add column pull-ups
Run ERC later
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