Arduino-esp32: HardwareSerial multiple definition

[atsteich]

I'm not really familar with the esp32, and I'm getting a real strange error...
I installed the esp32 in an local arduino ide, no other packages installed.

when running the following code:

`HardwareSerial Serial1(1);

define RXD2 16

define TXD2 17

void setup() {
Serial.begin(115200);
Serial1.begin(9600, SERIAL_8N1, RXD2, TXD2);
Serial.println("Serial Txd is on pin: "+String(TX));
Serial.println("Serial Rxd is on pin: "+String(RX));
}

void loop() {
while (Serial2.available()) {
Serial.print(char(Serial2.read()));
}
}`

I get an error message saying that there is a multiple definition of Serial1. I have absolutely no idea what I am doing wrong, since there are lot of examples using exactly this code...

When I remove the line " HardwareSerial Serial2(2) " the script can be compiled and uploaded, but still it is not working when I run some traffic on the specified pins.

[lbernstone]

The HardwareSerials should all be pre-allocated, so the objects are already there. The default pins for Serial1 are 9&10, for Serial2 they are 16&17. These pins are used for other hardware in some configurations (e.g. wrover modules). The serial ports can be assigned to any open I/O pins, so maybe try using 21&22 or others that aren't in use on your board. Make sure your code is consistent, as what you have posted here initializes Serial1 in one place, and then uses Serial2 later.

[atsteich]

Thanks for responding!

You are right, there shouldn't be any Serial2.xxx, but only Serial1.xxx.
Correcting this doesn't help, I still get the same error message. Changing the RX and TX pin is also not working...

Is nobody other having this problem?

[MarkusAD]

@atsteich @lbernstone kindly made clear that the names Serial/Serial1/etc are already defined, so to define them again is an error. You can refer to the uart as something else, however:

HardwareSerial GPS(1); // uart 1
void setup() {
  GPS.begin(9600, SERIAL_8N1, RXD2, TXD2);
}

[MarkusAD]

As @lbernstone said, you can use Serial1 without having to declare anything other than the Serial1.begin() line. If you still dont get any serial data, you've probably got the TX/RX lines swapped around. TX on the device should go to RX on the esp32 and RX on the device to TX on the esp32.

[larryn46]

I had a similar problem. My code was almost the same as yours. Just comment out the line
HardwareSerial Serial1(1);
to
// HardwareSerial Serial1(1);
Serial1 is already defined.

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