When a TXD serial port is sending data, how do I change a pin to low level and automatically change the pin to high level after the data is sent

[ShiPC123]

I used the following code

void setup() {
Serial1.begin(115200);
pinMode(PA0, OUTPUT);
digitalWrite(PA0, HIGH);
}

void loop() {
digitalWrite(PA0, LOW);
Serial1.println("12345678");
digitalWrite(PA0, HIGH);
}

But the delay() function must be added if it doesn't seem to work properly
Like this

void setup() {
Serial1.begin(115200);
pinMode(PA0, OUTPUT);
digitalWrite(PA0, HIGH);
}

void loop() {
digitalWrite(PA0, LOW);
Serial1.println("12345678");
delay(5);
digitalWrite(PA0, HIGH);
}

Is there a way to do this without adding a delay function

[fpistm]

USe Serial.flush(); instead of delay(5).

void setup() {
Serial1.begin(115200);
pinMode(PA0, OUTPUT);
digitalWrite(PA0, HIGH);
}

void loop() {
digitalWrite(PA0, LOW);
Serial1.println("12345678");
Serial1.flush();
digitalWrite(PA0, HIGH);
}

For ref: https://www.arduino.cc/reference/tr/language/functions/communication/serial/flush/

[ShiPC123]

I don't want to use delay because I want to use a non-blocking way to run the function, for example, I have a baud rate of 9600 and now I want to send 50 frames of data and it takes about 60ms. I don't want my code stuck here, is there any other way?

[fpistm]

There is no service to warn when all data sent in Arduino API (ie: callback).

[fpistm]

Just thinking of availableForWrite API, you can try to call it periodically (using HardwareTimer) and if the result equal the buffer size (SERIAL_TX_BUFFER_SIZE), it means all data were sent and so you can toggle your pin.
It is just thought, I have not tested.

[ShiPC123]

Thank you very much

[ShiPC123]

I found the following library file. How should I interpret the transmitDisableIRQ () function inside
https://github.com/PR-DC/PRDC_RS485HD_STM32/blob/main/src/PRDC_RS485HD_STM32.cpp

void PRDC_RS485HD_STM32::transmitDisableIRQ(serial_t obj) {
it = objs.find(&obj-> index);
PRDC_RS485HD_STM32 oRS485 = it-> second;
if(oRS485-> state == 1) {
oRS485-> state = 0;
if(oRS485-> pin_num) {
digitalWrite(oRS485-> enable_pin,LOW);
if(oRS485-> pin_num > 1) {
digitalWrite(oRS485-> enable_pin2,LOW);
}
}
}
}

[fpistm]

@ShiPC123, you can easily understand I can't study all user code. The only thing I can tell is that the library is for this core and it seems manage your use case to manage the pin. Up to you to use it or not or asking support to the library maintainer.