Serial trigger 1 byte is possible????

[tv4you2016]

Hardware:

Board	ESP32 Dev Module
Version/Date	2.0.0
IDE name	Arduino IDE
Flash Frequency	80Mhz
PSRAM enabled	no
Upload Speed	115200
Computer OS	Windows 10

Description:

Hey Good afternoon,

I have a doubt, and it is possible to make a trigger for each byte received by Serial.
I'm using the following code but it doesn't.

#include <Arduino.h>


#define PIN_NOT_RE 18   // LOW = Recived
#define PIN_DE 19  // HIGH = SEND

void setup() {
  // put your setup code here, to run once:

  Serial.begin(14400);
  Serial.setRxBufferSize(1);
  Serial.println(Serial.getTimeout()); // print the default value
  Serial.setTimeout(1);
  Serial.println(Serial.getTimeout()); // print the new value
  pinMode(4, OUTPUT);
  pinMode(PIN_NOT_RE, OUTPUT);
  pinMode(PIN_DE, OUTPUT);

  delay(5000);


  digitalWrite(4, HIGH);

  digitalWrite(PIN_NOT_RE, LOW);
  digitalWrite(PIN_DE, LOW);
}


void loop() {

}



void serialEvent() {

  if (Serial.available()) {
    digitalWrite(4, LOW);
    // get the new byte:
    char inChar = (char)Serial.read();
    digitalWrite(4, HIGH);
  }

}

[SuGlider]

@tv4you2016 ,

Please turn the debug level to verbose and check the messages, but be aware that some messages may be sent at baud rate 115200 because this is the default rate at boot time.

I can tell that Serial.setRxBufferSize(1); doesn't work given that the minimum RxBufferSize is 129 bytes.
RxBufferSize must be set before starting Serial port (Serial.begin(...))
Look at https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/HardwareSerial.cpp#L275-L289

Regarding your specific question, I've tested it with this sketch, and it worked fine:

#include <Arduino.h>

void setup() {
  Serial.begin(115200);
  Serial.println();
  Serial.println("Ready to receive bytes on UART.");
  Serial.println("It will output one byte per line with its HEX value.");
  Serial.flush(); 
}

void loop() {
}

void serialEvent() {
  if (Serial.available()) {
    char inChar = (char)Serial.read();
    Serial.print(inChar);
    Serial.print(" - 0x");
    Serial.print(inChar, HEX);
  }
  Serial.println();  // this line indicates that it has read a single byte at a time
}

[rottaran]

serialEvent is just called inbetween loop(), see

arduino-esp32/cores/esp32/main.cpp

Line 47 in 92ce408

if (serialEventRun) serialEventRun();

. Neither interrupts nor full buffers involved.

[SuGlider]

serialEvent is just called inbetween loop(), see

arduino-esp32/cores/esp32/main.cpp

Line 47 in 92ce408

if (serialEventRun) serialEventRun();

. Neither interrupts nor full buffers involved.

Yes, this is correct. Arduino has no API to trigger UART events based on ISR or Full buffers.
All it has is the serialEvent called in between loop() as you pointed out - but this is exactly the Arduino specification.
https://www.arduino.cc/en/Tutorial/BuiltInExamples/SerialEvent

[SuGlider]

A potential solution is being implemented.
It's the Serial.onReceive(function)

As soon as any data arrives UART RX, function() will called.