ESP_Midea/Midea_ESP/2X4_HEADER_PINOUT.md

2x4 Programming Header Pinout

Header J2 - 2x4 Programming Header (8 Pins Total)

This is a standard 2-row, 4-column header (2.54mm pitch) commonly used for programming headers.

Physical Layout

Top View:
┌─────────────┐
│ 1  2  3  4  │  ← Top row
│ 5  6  7  8  │  ← Bottom row
└─────────────┘

Pin Numbering:

• Top row (left to right): Pins 1, 2, 3, 4
• Bottom row (left to right): Pins 5, 6, 7, 8

Pin Assignment

Pin	Signal	ESP32 Connection	Description
1	+3V3	+3V3 Power Rail	Optional - Power ESP32 from programmer
2	GND	GND	Ground reference (required)
3	UART_TX	GPIO1 (UART0 TX)	ESP32 transmits to programmer
4	UART_RX	GPIO3 (UART0 RX)	ESP32 receives from programmer
5	DTR	GPIO0	Data Terminal Ready (auto-reset)
6	RTS	EN	Request To Send (auto-reset)
7	NC	-	Not connected (spare)
8	NC	-	Not connected (spare)

Connection to USB-to-Serial Adapter

USB-to-Serial Pin	J2 Pin	Signal	Notes
VCC (3.3V)	Pin 1	+3V3	Optional - only if powering ESP32 from adapter
GND	Pin 2	GND	Required - always connect
RX	Pin 3	UART_TX	Adapter RX receives from ESP32 TX
TX	Pin 4	UART_RX	Adapter TX sends to ESP32 RX
DTR	Pin 5	DTR	Auto-reset control
RTS	Pin 6	RTS	Auto-reset control
-	Pin 7	NC	Spare (not used)
-	Pin 8	NC	Spare (not used)

Important Notes:

• RX/TX are swapped - Adapter RX connects to ESP32 TX (Pin 3), and vice versa
• Do NOT connect VCC if ESP32 is already powered from J1 (JST connector)
• Always connect GND - critical for proper operation
• DTR and RTS enable automatic reset (no button pressing needed)

Advantages of 2x4 Header

1. Standard layout - Common 2.54mm pitch header format
2. More stable - 2-row design is more mechanically stable
3. Spare pins - Pins 7 and 8 available for future expansion
4. Easy to connect - Standard programming cable format
5. Prevents wrong orientation - 2-row design makes it harder to connect backwards

KiCad Symbol

Library: Connector_PinHeader_2.54mm
Symbol: PinHeader_2x04_P2.54mm_Vertical

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 (pins 1-6)
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. DTR/RTS signals automatically put ESP32 into boot mode
5. No button pressing required!

Future Expansion

Pins 7 and 8 are spare and can be used for:

• Additional UART (if needed)
• I2C (SDA/SCL) for debugging
• SPI (MISO/MOSI) for additional peripherals
• GPIO monitoring
• Or leave as NC (Not Connected)

---

Summary

2x4 Header Layout:

Top Row:    VCC  GND  TX   RX
Bottom Row: DTR  RTS  NC   NC

6 pins used (1-6) for programming
2 pins spare (7-8) for future use

This is a standard, stable, and convenient programming header configuration!