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Display Pin Configuration Reference

Overview

This document provides the complete pin configuration for connecting ST7735 displays to ESP32 and ESP32-S3 boards in the dual display billboard system.

Pin Assignments

ESP32 (ESP32DEV_MODE)

Used for ESP32 development boards with standard pinout

Function Pin GPIO Description
SPI Communication
MOSI 23 GPIO 23 SPI Data (Master Out Slave In)
SCLK 18 GPIO 18 SPI Clock
DC 14 GPIO 14 Data/Command (shared for both displays)
RST 26 GPIO 26 Reset (shared for both displays)
Display 1
CS1 10 GPIO 10 Chip Select for Display 1
BL1 7 GPIO 7 Backlight control for Display 1
Display 2
CS2 39 GPIO 39 Chip Select for Display 2
BL2 8 GPIO 8 Backlight control for Display 2
DCC Input
DCC 4 GPIO 4 Digital Command Control input signal

ESP32-S3 (ESP32S3_MODE)

Used for ESP32-S3-N8R2 modules with your specified pinout

Function Pin GPIO Description
SPI Communication
MOSI 11 GPIO 11 SPI Data (Master Out Slave In)
SCLK 12 GPIO 12 SPI Clock
DC 14 GPIO 14 Data/Command (shared for both displays)
RST 5 GPIO 5 Reset (shared for both displays)
Display 1
CS1 10 GPIO 10 Chip Select for Display 1
BL1 7 GPIO 7 Backlight control for Display 1
Display 2
CS2 39 GPIO 39 Chip Select for Display 2
BL2 8 GPIO 8 Backlight control for Display 2
DCC Input
DCC 4 GPIO 4 Digital Command Control input signal

Simplified Connection Table - ESP32

ESP32 Pin       →    Display 1    →    Display 2
──────────────────────────────────────────────────
3.3V            →    VCC          →    VCC (shared)
GND             →    GND          →    GND (shared)
GPIO 23 (MOSI)  →    SDA          →    SDA (shared)
GPIO 18 (SCLK)  →    SCL          →    SCL (shared)
GPIO 26 (RST)   →    RES          →    RES (shared)
GPIO 14 (DC)    →    DC           →    DC  (shared)
GPIO 10 (CS1)   →    CS           →    ─
GPIO 39 (CS2)   →    ─            →    CS
GPIO 7  (BL1)   →    BLK          →    ─
GPIO 8  (BL2)   →    ─            →    BLK
GPIO 4  (DCC)   →    DCC Input Signal

Simplified Connection Table - ESP32-S3

ESP32-S3 Pin    →    Display 1    →    Display 2
──────────────────────────────────────────────────
3.3V            →    VCC          →    VCC (shared)
GND             →    GND          →    GND (shared)
GPIO 11 (MOSI)  →    SDA          →    SDA (shared)
GPIO 12 (SCLK)  →    SCL          →    SCL (shared)
GPIO 5  (RST)   →    RES          →    RES (shared)
GPIO 14 (DC)    →    DC           →    DC  (shared)
GPIO 10 (CS1)   →    CS           →    ─
GPIO 39 (CS2)   →    ─                 →    CS
GPIO 7  (BL1)   →    BLK          →    ─
GPIO 8  (BL2)   →    ─            →    BLK
GPIO 4  (DCC)   →    DCC Input Signal

Step-by-Step Wiring Guide - ESP32

Power Connections - ESP32 (Do These First!)

CRITICAL: Use 3.3V only - 5V will damage displays!

Step 1: Power Rails
ESP32 3.3V  →  Breadboard + rail  →  Both Display VCC pins
ESP32 GND   →  Breadboard - rail  →  Both Display GND pins

SPI Bus Connections - ESP32 (Shared Between Displays)

These pins connect to BOTH displays:

Step 2: SPI Data & Clock
ESP32 GPIO 23 (MOSI)  →  Display 1 SDA  →  Display 2 SDA
ESP32 GPIO 18 (SCLK)  →  Display 1 SCL  →  Display 2 SCL

Step 3: Control Signals  
ESP32 GPIO 26 (RST)   →  Display 1 RES  →  Display 2 RES
ESP32 GPIO 14 (DC)    →  Display 1 DC   →  Display 2 DC

Individual Display Connections - ESP32

These pins are unique for each display:

Step 4: Display 1 Only
ESP32 GPIO 10  →  Display 1 CS  pin
ESP32 GPIO 7   →  Display 1 BLK pin

Step 5: Display 2 Only  
ESP32 GPIO 39  →  Display 2 CS  pin
ESP32 GPIO 8   →  Display 2 BLK pin

Step 6: DCC Input Connection
ESP32 GPIO 4   →  DCC signal input

Step-by-Step Wiring Guide - ESP32-S3

Power Connections - ESP32-S3 (Do These First!)

 CRITICAL: Use 3.3V only - 5V will damage displays!

Step 1: Power Rails
ESP32-S3 3.3V  →  Breadboard + rail  →  Both Display VCC pins
ESP32-S3 GND   →  Breadboard - rail  →  Both Display GND pins

SPI Bus Connections - ESP32-S3 (Shared Between Displays)

 These pins connect to BOTH displays:

Step 2: SPI Data & Clock
ESP32-S3 GPIO 11 (MOSI)  →  Display 1 SDA  →  Display 2 SDA
ESP32-S3 GPIO 12 (SCLK)  →  Display 1 SCL  →  Display 2 SCL

Step 3: Control Signals  
ESP32-S3 GPIO 5  (RST)   →  Display 1 RES  →  Display 2 RES
ESP32-S3 GPIO 14 (DC)    →  Display 1 DC   →  Display 2 DC

Individual Display Connections - ESP32-S3

These pins are unique for each display:

Step 4: Display 1 Only
ESP32-S3 GPIO 10  →  Display 1 CS  pin
ESP32-S3 GPIO 7   →  Display 1 BLK pin

Step 5: Display 2 Only  
ESP32-S3 GPIO 39  →  Display 2 CS  pin
ESP32-S3 GPIO 8   →  Display 2 BLK pin

Step 6: DCC Input Connection
ESP32-S3 GPIO 4   →  DCC signal input

ST7735 Display Wiring

Display Module Pins (typical ST7735 breakout)

  • VCC → 3.3V (DO NOT use 5V)
  • GND → Ground
  • SCL/SCLK → SPI Clock pin (GPIO 12 for ESP32-S3, GPIO 18 for ESP32)
  • SDA/MOSI → SPI Data pin (GPIO 11 for ESP32-S3, GPIO 23 for ESP32)
  • RES/RST → GPIO 5 for ESP32-S3, GPIO 26 for ESP32 (shared between both displays)
  • DC/A0 → GPIO 14 (shared between both displays)
  • CS → GPIO 10 (Display 1) or GPIO 39 (Display 2) for both platforms
  • BLK/LED → GPIO 7 (Display 1) or GPIO 8 (Display 2) for both platforms

Notes

Power Requirements

  • Voltage: 3.3V only - DO NOT connect to 5V
  • Current: Each display draws ~20-50mA depending on content and backlight
  • Total system: ~100-150mA for dual displays

SPI Configuration

  • Mode: SPI Mode 0 (CPOL=0, CPHA=0)
  • Speed: 40MHz (optimized for ST7735)
  • Bit Order: MSB First

Display Specifications

  • Resolution: 160x80 pixels (ST7735_GREENTAB160x80)
  • Color: 16-bit RGB565
  • Orientation: Portrait (80x160) or Landscape (160x80)

Troubleshooting

  1. No display: Check power (3.3V), connections, and CS pins
  2. Garbled display: Verify SPI pins (MOSI, SCLK, DC)
  3. Wrong colors: Check RGB order in configuration
  4. Flickering: Check power supply stability and backlight control

Hardware Testing Checklist

Before Power-On

  • Verify all connections match pin table above
  • Confirm 3.3V power (NOT 5V)
  • Check for short circuits
  • Ensure CS pins are correctly connected (different for each display)

After Power-On

  • Check system boots correctly (serial monitor)
  • Verify display initialization messages in log
  • Test backlight control (displays should light up)
  • Confirm both displays show content
  • Test image upload and display functionality

Common Issues

  • Power: Insufficient power can cause boot loops or display corruption
  • DCC signal: Ensure DCC signal is properly isolated and at correct voltage levels

Configuration Validation

Current pin configuration is automatically selected based on the build environment:

  • esp32s3-st7735-debug: Uses ESP32-S3 pinout
  • esp32dev-st7735-debug: Uses ESP32 pinout

Check the serial monitor during boot for pin configuration confirmation.