ESP32 Serial.setDebugOutput

[Xylopyrographer]

For the ESP32 can someone shed light on Serial.setDebugOutput()?

Only info I can find is from the ESP8266 docs on Serial here, where it states:

By default the diagnostic output from WiFi libraries is disabled when you call Serial.begin. To enable debug output again, call Serial.setDebugOutput(true). To redirect debug output to Serial1 instead, call Serial1.setDebugOutput(true).

You also need to use Serial.setDebugOutput(true) to enable output from printf() function.

I see the function is in the current core libraries (HardwareSerial.h for example), and I can trace it through to the lower level libraries but does it affect anything?

Is this lingering code from porting from the ESP8266 to the ESP32?

.print(), .println(), .printf(), log_x(), and LOG_X() all work OK without ever using .setDebugOutput( true ) ( even with using WiFi).

Is it turned on by default somewhere in the 'Serial' libraries?

[mrengineer7777]

In my experience .setDebugOutput(true) doesn't seem to do anything.

[me-no-dev]

It actually does, but I think it's ON for Serial by default. If you want to have the output on some other port (Serial1, USB, etc) then it will be switched. We should have it off by default though, so maybe @SuGlider can have a look

[SuGlider]

Sorry for the long delay in answering it. For the records:

HardwareSerial::setDebugOutPut(bool) sets the Serial port (UARTx) to output DEBUG information using the Arduino log_x() where x is d for debug, e for error or i for information log messages.

By default, right after booting, Logging is set to output using UART0 (console serial port).
If the user wants to mute all log_x() output, Serial.setDebugOutput(false) will do the job.
Serial.end() also does the same, among other things, such as detaching UART pins.

By other hand Serial1.setDebugOutput(true) would set all the log messages to be sent to UART1.
Only 1 serial port can output log messages. The last Serial port that set DebugOutput to true will be used.

Let's say that I want to use UART0 for connecting to an external device, but I also want to see the logging into UART1.
The code for that shall be:

Serial.begin(9600);  // connected to an external UART hardware
Serial1.begin(115200);  // Our log messages port
Serial1.setDebugOutput(true);  // enables logging to be sent to UART1 and not to UART0 anymore
log_i("This log message goes to Serial1!");

Details:

setDebugOutPut(true) sets a function pointer in ROM ETS PUTC1, which in turn is used by ROM ets_printf(), which is used by IDF and Arduino log functions. Therefore, it just points the ets_install_putc1() to a void function that writes a character to the UARTx FIFO in order to transmit it through the Serial Port.