Serial not working after wakeup

[tatulea]

Hi,

I am using a button to put Arduino in sleep mode and wake it up, but the Serial is not working anymore after it is waking up. What should I do?

#include "ArduinoLowPower.h"

volatile bool just_wakeup = true;

// Pin used to trigger a wakeup
const int pin = 0;

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(pin, INPUT_PULLUP);
}

void loop() {
  if (just_wakeup) {
    just_wakeup = false;
    delay(3000);
    Serial.begin(115200);
  }
  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(LED_BUILTIN, LOW);
  delay(500);
  Serial.println("test");

  if (digitalRead(pin) == LOW) {
    Serial.end();
    delay(500);
    LowPower.attachInterruptWakeup(pin, wakeup_handler, FALLING );
    LowPower.deepSleep();
  }
}

void wakeup_handler() {
  just_wakeup = true;
  detachInterrupt(pin);
}

[facchinm]

Hi @tatulea, wakeup/standby with the USB connected is super tricky since it depends on the operating system/USB controller the board is connected to.
Would you mind sharing your PC or Mac configuration (both software and hardware) so I can try reproducing it? Thanks

[tatulea]

Hi,

I am using Windows 10 and Arduino IDE.
The PC is a HP EliteDesk 800 with intel I5-6500.

[grezco]

Hello,

I have the same problem with MKR WiFi1010 (and MKR1000) - Win10

[sashkaw]

Hello,

I also have the same problem with the Arduino WiFi MKR 1010 and MacBook Pro running OS X Yosemite.

[facchinm]

@tatulea @grezco @Durasno can you take a look at #8 ? Let me know if the proposed behaviour could work for you.

[grezco]

Hi @facchinm,

For me, it's the same problem.
At the wake up, the com port is present but even after closed serial monitors and reopened after a successful resume, I don't have serial print event.

[facchinm]

@grezco which operating system/PC are you using?

[grezco]

Windows 7 and Windows 10

[sashkaw]

@tatulea @grezco @Durasno can you take a look at #8 ? Let me know if the proposed behaviour could work for you.

Hi @facchinm,

The below script (based on the TimedWakeup example) seems to be working relatively well (after brief testing with Arduino WiFi MKR 1010, MacBook Pro + OS X Yosemite) with the changes from #8. The added delay is from a LowPowerLab/LowPower SAMD21 example sketch.

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  // Uncomment this function if you wish to attach function dummy when RTC wakes up the chip
  LowPower.attachInterruptWakeup(RTC_ALARM_WAKEUP, dummy, CHANGE);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(LED_BUILTIN, LOW);
  delay(500);
  
  while(!SerialUSB);
  delay(1000); 
  SerialUSB.println("Just woke up!");
  
  // Triggers a 2000 ms sleep (the device will be woken up only by the registered wakeup sources and by internal RTC)
  // The power consumption of the chip will drop consistently
  LowPower.sleep(2000);
}

void dummy() {
  // This function will be called once on device wakeup
  // You can do some little operations here (like changing variables which will be used in the loop)
  // Remember to avoid calling delay() and long running functions since this functions executes in interrupt context
}