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ESP_Midea/Midea_ESP/PROGRAMMING_HEADER.md
nearxos cf6e6e3baf Initial KiCad project
2026-01-06 02:05:24 +02:00

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Programming Header Pinout

Header J2 - 2x4 Programming Header (8 Pins)

Use this header to connect an external USB-to-Serial adapter (CP2102, CH340, FT232, etc.) for flashing the ESP32.

Pinout (Top View)

┌─────────────┐
│ 1  2  3  4  │  ← Top row
│ 5  6  7  8  │  ← Bottom row
└─────────────┘
Pin Signal ESP32 Connection Description
1 +3V3 +3V3 Power Rail Optional - Power ESP32 from programmer
2 GND GND Ground reference
3 UART_TX GPIO1 (UART TX) ESP32 transmits to programmer
4 UART_RX GPIO3 (UART RX) ESP32 receives from programmer
5 DTR GPIO0 Data Terminal Ready (auto-reset for flashing)
6 RTS EN Request To Send (auto-reset for flashing)
7 NC - Not connected (spare)
8 NC - Not connected (spare)

Connection to USB-to-Serial Adapter

When connecting your USB-to-Serial adapter:

Adapter Pin J2 Pin Signal
VCC Pin 1 +3V3 (optional - only if powering ESP32 from adapter)
GND Pin 2 GND
RX Pin 3 UART_TX (receives TX from ESP32)
TX Pin 4 UART_RX (sends to RX of ESP32)
DTR Pin 5 DTR (auto-reset)
RTS Pin 6 RTS (auto-reset)
- Pin 7 NC (spare)
- Pin 8 NC (spare)

Important Notes:

  • Do NOT connect VCC if your ESP32 is already powered from J1 (JST connector power input)
  • Always connect GND - this is critical for proper operation
  • RX/TX are swapped - Adapter RX goes to ESP32 TX, and vice versa
  • DTR and RTS enable automatic reset during flashing (no need to press buttons)

Optional Pull-up Resistors

For maximum reliability, add pull-up resistors:

  • R5: 10kΩ between J2 Pin 5 (DTR) and +3V3
  • R6: 10kΩ between J2 Pin 6 (RTS) and +3V3

Most USB-to-Serial adapters have built-in pull-ups, but adding them on the board ensures reliable operation.

Flashing Process

  1. Connect USB-to-Serial adapter to J2 header
  2. Power the board (via J1 JST connector or J2 Pin 1)
  3. Use esptool or ESPHome to flash: 
    esptool.py --port /dev/ttyUSB0 write_flash 0x0 firmware.bin
  4. The DTR/RTS signals will automatically put ESP32 into boot mode

Common USB-to-Serial Adapters

  • CP2102: Common, reliable, good driver support
  • CH340: Very common, cheap, good for Linux
  • FT232: Premium option, excellent driver support
  • PL2303: Older, less reliable

All of these will work with this header configuration.