UART Test using example code.

[swpmx]

Does the example teensy "EchoBoth" sketch require any external hardware for this line to become true for Teensy 3.2:

if (HWSERIAL.available() > 0) {

This line is never true when I run the sketch when nothing is connected to pins 0 (RX) and 1 (TX).

#define HWSERIAL Serial1

void setup() {
Serial.begin(9600);
HWSERIAL.begin(38400);
}

void loop() {
int incomingByte;

if (Serial.available() > 0) { /// <----- This line works fine and is true when data is entered
incomingByte = Serial.read();
Serial.print("USB received: ");
Serial.println(incomingByte, DEC);
HWSERIAL.print("USB received:");
HWSERIAL.println(incomingByte, DEC);
}
if (HWSERIAL.available() > 0) { /// <------This line is never true.
incomingByte = HWSERIAL.read();
Serial.print("UART received: ");
Serial.println(incomingByte, DEC);
HWSERIAL.print("UART received:");
HWSERIAL.println(incomingByte, DEC);
}
}

 

[stevech]

? when nothing is connected to pins ?

 

[swpmx]

Only the USB cable is plugged into the Teensy 3.2 all other pins are not connected.

What is required for (HWSERIAL.available() >0) to be true (greater than 0)?

 

[robsoles]

...

What is required for (HWSERIAL.available() >0) to be true (greater than 0)?

expected: Serial device (including, certainly not limited to, another Teensy) connected to the appropriate pins on Teensy AND transmitting appropriately.

 

[stevech]

Only the USB cable is plugged into the Teensy 3.2 all other pins are not connected.

What is required for (HWSERIAL.available() >0) to be true (greater than 0)?

Quick read.... I'd say that something needs to send data to the RX pin.
A "loop-back" test would be to connect the TX pin to the RX pin. Then send a character to the hardware serial port and see if receive it.

 

[swpmx]

Quick read.... I'd say that something needs to send data to the RX pin.
A "loop-back" test would be to connect the TX pin to the RX pin. Then send a character to the hardware serial port and see if receive it.

OK, thanks. That is what I wanted to know. It does require connections to RX pin before the Serial.available will be true then.


Thanks for the responses.

 

[jonr]

Not only a connection, but a byte has to be received.