Port Open fails with T3.5, works with T3.2

[paynterf]

Hi,

I have a simple two-line program

void setup()
{
	Serial.begin(115200);
	Serial.println("Starting Teensy");
  /* add setup code here */

}

This compiles and works fine with a T3.2, but when I compile this same program for a T3.5 & upload, I get a 'Port failed to open' error. I have tried this trick with two different T3.5's with the same result.

I have verified that the Tools->Serial option is set for 'Serial', and I have tried using the reset button to make sure the 3.5 is in programming mode - no luck.

Am I missing something here?

TIA,

Frank

 

[Theremingenieur]

T3.5 is probably too fast and starts Serial.println(whatever) before the other side is ready to receive data after just having been initialized with Serial.begin().

Add a delay(100) after Serial.begin() and check if this helps. Adapt the delay time if needed.

 

[Projectitis]

To add to what Theremingenieur says, in my latest project (on T3.6) I've had to add a delay(2000) after Serial.begin. Anything less hasn't worked! Your situation may be different.

 

[defragster]

If you want to see first Serial prints something like this is best. Results also vary with choice of SerMon The startup time will be changing with next beta #4 and release of TD 1.42 - this will still work. In TD_1.42 PJRC is including a teensy_sermon smarter alternative to the IDE SerMon that will show under 'Tools / Ports'.

  Serial.begin(115200);
  while (!Serial && millis() < 3000 ) ;
  Serial.print( "Teensy Online @ millis=" );
  Serial.println( millis() );

This will wait up to 3 seconds for Serial to appear - and after that connected to USB or not - it will continue

 

[paynterf]

Thanks for the quick replies, but it's still not working for me. I added a couple of lines in loop() to blink the built-in LED, so I know the program is actually uploading and running OK. If I change the delay time around the loop and reupload, the built-in LED behavior changes appropriately. However, even with the code suggested by defragster (and even with the time in the 'while' statement increased to 13000) I still don't get any printout.

Interestingly though, the 'while' statement clearly falls through to loop() after about 6 seconds, even with the timeout value set to 13000. So it appears that the '!Serial' portion of the AND statement goes FALSE before the 13000 millisec timeout elapses, but I still don't get any prints.

I also changed the baud rate around a bit, but that doesn't effect anything.

Of course, this all works fine on the T3.2 - here's the code

const int LED_PIN = 13;


void setup()
{
	Serial.begin(115200);
	while (!Serial && millis() < 13000);
	Serial.print("Teensy Online @ millis=");
	Serial.println(millis());
	Serial.println("Starting Teensy");

	pinMode(LED_BUILTIN, OUTPUT);

  /* add setup code here */

}

void loop()
{
	bool status = digitalRead(LED_BUILTIN);
	digitalWrite(LED_BUILTIN, !status);
	delay(1250);
	Serial.println("blink");

  /* add main program code here */

}

and here's the printout from the T3.2

Opening port
Port open
Teensy Online @ millis=3412
Starting Teensy
blink
blink
blink
blink
blink
blink
blink

Port closed

Frank

 

[defragster]

That is ODD - even on the T_3.2 - I've seen it take 2000 or 2500 millis with IDE SerMon - but not anything over 3400?

Try TyCommander - it is what I use and it works much better in general.

Or update to TD_1.42 Beta 3 - it has the improved teensy_sermon in early debug state and it might give feedback Paul can use to help.

And as KurtE notes below - I've not seen any trouble on T_3.5 or T_3.6

 

[KurtE]

Works fine on one of my T3.5s... I am currently running current beta plus TyCommander...

Teensy Online @ millis=388
Starting Teensy
blink
blink
blink
blink
blink
blink
blink
blink
blink
blink
blink