[Solved] Multiple VirtualWrites causing red SOS blink

Need Help With My Project
1

This has been a very strange issue. I am pushing data to 2 virtual pins, temperature and humidity from a DHT22 sensor. I am using the PietteTech_DHT library. However it seems if I push the temp and humidity values from the readings it causes my Photon to crash and do a red SOS blinking. If I hard code in say some int values like 5 and 6, it works just fine. But what is strange is that doing just one virtualWrite works just fine with the actual sensor values. Blynk Debug output has nothing that I can see of value. It just crashes and restarts.

Heres my stripped down code:

//#define BLYNK_DEBUG // Optional, this enables lots of prints
//#define BLYNK_PRINT Serial

#include "blynk/blynk.h"

char auth[] = "0123456789abcd";

#include <math.h>

// This #include statement was automatically added by the Particle IDE.
#include "PietteTech_DHT/PietteTech_DHT.h"

double temp                         = 0;
double humidity                     = 0;

#define DHTTYPE  DHT22       // Sensor type DHT11/21/22/AM2301/AM2302
#define DHTPIN   3           // Digital pin for communications

void dht_wrapper(); // must be declared before the lib initialization

PietteTech_DHT DHT(DHTPIN, DHTTYPE, dht_wrapper);

Timer blynk_timer(15000, blynkPublish);
Timer environment_timer(600000, environmentPublish);

void setup(){

    Particle.variable("g_temp", temp);
    Particle.variable("g_humidity", humidity);

	delay(1000);

    environmentPublish();

	delay(1000);

    blynk_timer.start();
    environment_timer.start();

    Particle.publish("End of setup");
    
    Blynk.begin(auth);

}

void dht_wrapper(){
    DHT.isrCallback();
}

void loop(){

    Blynk.run();

}

void blynkPublish(){

    if(Blynk.connected()){

       /* This failes */
        Blynk.virtualWrite(V0, temp);  // temp shows up like 70.2 when I view the variable
        Blynk.virtualWrite(V1, humidity); // humidity shows up like 50.4 when I view the variable

       /* 
       This is fine
        Blynk.virtualWrite(V0, 5);
        Blynk.virtualWrite(V1, 6);

        */


    }

}

void environmentPublish(){

    DHT.acquireAndWait();

    delay(500);

    temp = DHT.getFahrenheit();
    humidity = DHT.getHumidity();

    temp = round(temp*10)/10.0;
    humidity = round(humidity*10)/10.0;

    Particle.publish("temp", String(temp), 60, PRIVATE);
    Particle.publish("humidity", String(humidity), 60, PRIVATE);

}
2
  1. Timer is not running, no timer library is included… I recommend using ‘sparkcorepolledtimer’ library
  2. Red SOS is unlikely to be caused by Blynk.

Debug:

  1. Try getting sensor data without Blynk in intervals
  2. Try bare Blynk example without modifications
  3. When you have succeded, combine both
3

  1. Timers are included by default. See https://docs.particle.io/reference/firmware/photon/#software-timers

  2. It only happens when I use blynk. The original sketch has been working for over a year with no issues prior to me adding blynk.

I’ve spent hours troubleshooting this and I’ve taken this down to the simplest forms I can think of. I can get data just fine from sensor. I can also send data to blynk. The breaking point has been when I do two virtual writes in this particular sketch. What is strange is that I am using blynk on a different device and I am sending 3 virturalwrites in succession with no issue. It seems to be something with the data type/formating or combination of something in this particular sketch. I’m just failing to find the needle in the haystack.

4

Could you try putting a small delay (20-50ms) between writes?

5

I submitted the same issue to the particle forums and got a response that helped me stop the crashing. I changed my datatypes for temp and humidity to String. In my environmentPublish() I did this:

void environmentPublish(){

    DHT.acquireAndWait();

    temp = String::format("%.1f",DHT.getFahrenheit());
    humidity = String::format("%.1f",DHT.getHumidity());
    
    Particle.publish("librato_garage_temp", temp, 60, PRIVATE);
    Particle.publish("librato_garage_humidity", humidity, 60, PRIVATE);
}

Now the string data pushes to Blynk with no issues. So its not really solved but it no longer crashes.

6

This is VERY strange. The same operations are basically performed inside Blynk library…

7

I would not put a Blynk operation in a timer like that. Timer functions need to execute quickly. Set a Boolean in the timer and send in the main loop.