Serial is freezing arduino

Question

I'm using a LinkIt ONE Arduino-like to send sensor data via MQTT.

It always worked very well, then out of the blue, it stopped printing anything using Serial.print();

But if I ommit the "Serial.begin(9600);" line, the code runs normally, sending sensor data via MQTT, even if I can't see debug output.

This shows the problem is on the Serial handling.

Since I can't show the entire code here, here's two test cases:

1.

void setup(){
  Serial.begin(9600);
  Serial1.begin(9600);
  while(!Serial); //Wait until Serial is ready before printing
}
void loop() {

  Serial1.println("This came from serial 1"); //does nothing
  Serial.println("This came from serial 0");  //works
  delay(1000);
}

It shows me the following output:

This came from serial 0

This came from serial 0

Thi

Looks like the module freezes before the third iteration.

But if I omit the lines that aren't printed, from Serial1:

2.

void setup(){
  Serial.begin(9600);
  while(!Serial);  //Wait until Serial is ready before printing
}
void loop() {
  Serial.println("This came from serial 0");  //works
  delay(1000);
}

No output is shown on Serial monitor.

What is the reason behind this? Since Serial1 prints nothing, why can't I remove it?

Observations:

I tested the code in two LinkIt ONE modules of the same model.

I tested it in Arduino SDK 1.6.8, 1.5.6r2 and 1.6.5.

Edit:

Just made another test using the code below. It blinked two times showing that

Serial.begin(9600); runs

while(!Serial); runs (it didn't freeze the module waiting for Serial to initialize)

But Serial.println(); freezes

void setup(){
  pinMode(13, OUTPUT);
  blink();
  Serial.begin(9600);
  blink();
  while(!Serial); //Wait until Serial is ready before printing
}
void loop() {

  Serial.println("This came from serial 0");  //works
  blink();
  delay(1000);
}
void blink(){
  digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);               // wait for a second
  digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);
}

score 1 · Accepted Answer · answered May 22 '16 at 16:53

1

The problem was solved by:

making a clean install of Arduino IDE 1.6.9
uploading the LinkIt SDK on board manager from version 1.1.17 to 1.1.23.

Then the Serial function returned back to normal.

answered May 22 '16 at 16:53

Paulostation

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1
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score 0 · Answer 2 · answered May 17 '16 at 21:57

I have bit similar problem. I thing, this is arduino bug. When start serial port, must be take out data from Rx. When read buffer overflow my arduino freeze. I can't run delay because when arduino wait, serial port can receive lot of data -> overflow -> freeze. Instead of delay I use own function wait(milis):

void wait(unsigned long wait_time){
  unsigned long start_time;
  start_time=millis();
  while ( millis() < (start_time+wait_time) ){
    if (serial.available() > 0) serial.read();
  }
}

score -1 · Answer 3 · answered May 16 '16 at 16:58

This shows the problem is on the Serial handling.

The problem isn't actually in Serial, it's somewhere else. Many things are able to make the Arduino hang in mid-write. Show us the any code that you have written, plus links to the libraries you are using, and you'll have your answer in short order.

I will guess that you have a low-RAM condition, perhaps exacerbated by heap usage. Do you use String? I notice you're not using the F macro to save RAM.

Serial is freezing arduino

3 Answers3