GPIO Pinout

The ESP32-CAM (AI-Thinker) has severe GPIO constraints. The OV2640 camera claims 15 pins, the SD card claims 6, and PSRAM uses GPIO16.

Camera pins (OV2640)

GPIO	Function	Notes
0	XCLK	Also BOOT pin — pull LOW to enter flash mode
5	VSYNC
18	PCLK
19	D7
21	D6
22	D5
23	D4
25	D3
26	D2
27	D1
32	PWDN	Camera power down control
34	D0	Input only
35	HREF	Input only
36	SIOC (SCL)	Input only
39	SIOD (SDA)	Input only

SD card pins (4-bit mode)

GPIO	Function	Notes
2	DATA0	Also affects boot (must be LOW or floating)
4	DATA1	Also connected to onboard LED flash
12	DATA2	Must be LOW during boot
13	DATA3
14	CLK
15	CMD

PSRAM

GPIO	Function	Notes
16	PSRAM CS#	Not available — connected to PSRAM chip select

Danger

Using GPIO16 while PSRAM is enabled causes watchdog triggers and boot loops. Never configure GPIO16 as a general-purpose pin on ESP32-CAM.

Available pins for LoRa UART

GPIO	Default Function	Availability
1	U0TXD (Console TX)	Available if serial console is sacrificed
3	U0RXD (Console RX)	Available if serial console is sacrificed
13	SD DATA3	Available if SD card uses 1-bit mode or is disabled
14	SD CLK	Available if SD card is disabled

LoRa UART: Option 1 — GPIO 1/3 (recommended for production)

Repurpose the programming/console UART for LoRa communication.

#define LORA_UART_NUM      UART_NUM_0
#define LORA_UART_TX_PIN   GPIO_NUM_1
#define LORA_UART_RX_PIN   GPIO_NUM_3

Pros:

• Pins are already wired and physically accessible
• Keeps PSRAM and SD card fully available
• Clean hardware design

Cons:

• No serial console output for debugging
• Must disconnect LoRa module to flash via UART
• Requires OTA for field updates

LoRa UART: Option 2 — GPIO 13/14 (development alternative)

Use SD card pins for UART.

#define LORA_UART_NUM      UART_NUM_1
#define LORA_UART_TX_PIN   GPIO_NUM_13
#define LORA_UART_RX_PIN   GPIO_NUM_14

Pros:

• Keeps serial console for debugging
• Can still flash normally via UART

Cons:

• Loses SD card functionality (or must use 1-bit mode, losing GPIO13)
• GPIO14 shared with SD CLK

Wiring diagram (Option 1)

ESP32-CAM          RYLR896/998
─────────          ───────────
GPIO1 (TX) ──────▶ RXD
GPIO3 (RX) ◀────── TXD
3.3V ──────────── VDD
GND ───────────── GND