Arduino Uno R3 Serial Communication with ESP32CAM without TTL

[mxmxmxmx]

I am currently trying to achieve serial communication between my ESP-32 Cam and Arduino Uno R3, as there is a host of sensors I would like to record data from into the Arduino Uno and then send to the ESP32-CAM. However, as I do not have a TTL adapter, I am forced to program the ESP32-CAM via the Arduino Uno itself. This has left me with a host of challenges.

So far, I understand that the Arduino Uno only has one hardware UART (pins 0 and 1), so as such I have tried to define a SoftwareSerial at pins 4 and 5 to act as RX and TX for the desired serial communication between ESP32CAM. Additionally, since I do not require an SD card, I have established GPIO pins 12 and 13 for use as the resulting RX TX.

The reason I have done this is because it seems as though VoR and VoT & pins 0 and 1 on the Arduino are required to be used during upload of code from Arduino IDE to the ESP32-CAM via the Arduino. To upload the code to the ESP32-CAM, I used the following connections in the image. Then, after upload, I removed the GPIO0-ground connection (to get it out of programming mode), and after hitting the reset button on the ESP32-CAM, I disconnected everything except for 5V and ground pins from the ESP32-CAM including VoR and VoT connections. Then, I uploaded the Arduino code but I cannot see anything pop up on the Serial Monitor of the ESP32.

I am not sure why that is; and I was wondering if my understanding of being able to use GPIO 12 and 13 is correct?

I noticed there was also GPIO16 which can be used for receiving (I only need communication one-way from Arduino to ESP32) but I thought it might be tricky without a partnering TX port. I have also tried uploading the ESP32-CAM code and once uploaded, switched the VoR and VoT connections to the serial ports I designated but that did not work either. Any help in helping achieve serial communication from the Arduino Uno to the ESP32-CAM would be greatly appreciated.

//ESP32 code: using pins 12 and 13 for RX and TX on ESP32

#define RXD2 GPIO_NUM_12
#define TXD2 GPIO_NUM_13

void setup() {
	Serial.begin(9600);
	SerialH.begin(9600, SERIAL_8N1, RXD2, TXD2); //serial for Uno-ESP32CAm
}
void loop() {
	if(SerialH.available()) {
		char data = SerialH.read();
		Serial.println(data); //printing to serial monitor to verify data is correct
	}
}

//Arduino: using RX and TX as pins 4 and 5 on Arduino

	#include <SoftwareSerial.h>
	
	#define RX_PIN 4
	#define TX_PIN 5
	
	SoftwareSerial sSerial(RX_PIN, TX_PIN);
	
	void setup() {
		Serial.begin(9600);
		sSerial.begin(9600);
	}
	
	void loop() {
		if (Serial.available()) {
			sSerial.write(22); //sending simple integer
		  delay(2000);
		}
	}

[srnet]

Well first off the ESP32CAM is 3V3 logic levels and the UNO is 5V logic levels, comms might work without a logic level shifter or they might not.

GPIO16 is the PSRAM select for the ESP32CAM and whilst you could use it for other stuff the picture size would then be limited to 800x600, larger images require the use of the PSRAM.

GPIO12 can be used but you need to be sure to leave it floating during programming or reset as its used internally by the ESP32 to sense the correct voltage for the Flash.

Much easier to use a USB to serial adapter to program the ESP32CAM.