Important: Reinitialise if sensor disconnects

[raako71]

In my usage I had a float variable for the sensor value, which I used in this section of code. Since the example doesn't have such a variable, I re-read the value.
Very important to have such a section of code for example if the sensor is connected by a non perfect connector

[ladyada]

is NaN really the value returned if it gets disconnected?

[raako71]

if it gets disconnected it will show (and hold) an incorrect value, if you reconnect it, it will show NaN. In my sketch I used the sleepydog library, basic idea I used is here. The key point being that watchdog will still reset once reconnected

// declare variables
float t = 0;
float t2 = 0;

// loop
t = bme.readTemperature();

// No sensor
if(t != t2){
Watchdog.reset();
//Serial.print(" Watchdog reset.");
}
t2 = t;
if(isnan(t)){
bme.begin(0x76);
Serial.print("\n reinitialise BME280 \n");
}

[khoek]

@ladyada Yes. Line 420 of Adafruit_BME280.cpp explicitly returns NAN: https://github.com/adafruit/Adafruit_BME280_Library/blob/master/Adafruit_BME280.cpp#L420

[caternuson]

Disconnect also potentially implies a power cycle and return to power on default state, losing any configuration done, like in init() or even by user. Does simply catching the NaN also result in everything else working as expected?

[khoek]

Certainly not, but the pull requester just proposes to change the simple example file. At any rate, I was just pointing out a misconception I noticed in the original reply.

…

On Fri, 30 Jul 2021, 07:32 Carter Nelson, ***@***.***> wrote: Disconnect also potentially implies a power cycle and return to power on default state, losing any configuration done, like in init() or even by user. Does simply catching the NaN also result in everything else working as expected? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#87 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AADSU3VSBNEFDLVCWLIZ453T2HCFZANCNFSM4QEZIKUA> .

[caternuson]

Oh, I see, begin() gets called when nan is detected. This should really be done in user code. That way any non-default usage of begin() can be taken care of as well. Looks like that's suggested above in the code example?

[caternuson]

Going to close this. If this continues to be a problem, please first open an issue.