ESP8266 (ESP-07), DHT22, web server - After some time, the page does not display.

Question

I copied the program alive from this page:
ESP8266 DHT11/DHT22 Temperature and Humidity Web Server with Arduino IDE .

Unfortunately, after a long time (1 - 2 days) the web page stops displaying in the browser. You can see that the device is alive, as the blue LED on the board flashes when messages are sent to the serial port.
Has anyone encountered a similar case and can make any suggestions?
The circuit is connected as shown in this diagram:
Link .

khoam · Answer

With which version of the ESP8266 board manager did you compile the program? The latest version is 2.6.3.

kaczakat · Answer

Check the performance of the site by sending some counter seconds. This will eliminate the hanging caused by DHT. Sometimes someone complains that every now and then the sensor can hang up and only unplugging the power supply helps. I haven't noticed this, but I haven't tested the operational stability for a long time. Such sensor can be powered from uC pin and if it stops responding do ON/OFF. But this needs to be handled somehow in code.

khoam · Answer

. In this program you provided a link to, the loop() does not check the current status of the WiFi client at all (the ESP is running in STA mode) - this could also be the cause of this behaviour. You can verify this by trying to unpin the ESP when the page stops displaying.

sq9etc · Answer

. Where can this be checked? Arduino IDE 1.8.12 As for the version of the ESP8266 support library that displays in the board manager, yes, it is version 2.6.3.

khoam · Answer

. Yes, that's what I meant. Try testing pinging to ESP when you can't access the site.

sq9etc · Answer

. I also have this problem. When I combined the linked program with this Network Time Protocol I had this effect. I added myself a date and time display on the page in addition to temperature and humidity. After a few tens of minutes, up to a few hours, the readings from the DHT would stop appearing and the time would change. I added something such that when 3 times the sensor would not return the correct values I would do an ESP.reset. Unfortunately this did not help. I had to switch the power to the circuit off and on. After that it worked for a while and then it was the same thing again. I had the module reset over and over again after every three failed attempts to read from the DHT. Added after 4 [minutes]: . I hadn't thought of that ping, that's a thought. If it happens I'll check it out. For now it has been working for almost two days.

khoam · Answer

For handling DHT11/22 sensors, a far better library for ESP is DHTesp than Adafruit, among other things, better error diagnostics for DHT.

sq9etc · Answer

Possibly, maybe I'll check at some point. But this behaviour of the sensor suggests that it's not a software problem, well unless it's the sensor's firmware. After a reset I think everything should re-initialise and work normally.

sq9etc · Answer

. This happened to me again today. This is what a snippet of a dump to a file from RealTerma looks like: Code: text Expand Select all Copy to clipboard... Local time: 2020-04-03 07:20:49 Temperature: 22.00ÂşC Humidity: 48.70% 020-04-03 07:20:49 Local time: 2020-04-03 07:20:59 Temperature: 22.00ÂşC Humidity: 48.70% Soft WDT reset >>>stack>>> ctx: sys sp: 3fffed40 end: 3fffffb0 offset: 01b0 3fffeef0:  40242a1c efd8a1fc 60000600 4021223d   3fffef00:  00000000 3ffed558 00000000 00000000   3fffef10:  40231530 3ffed558 3ffee510 60000600   ... 3fffff90:  3fffdad0 00000000 3ffeed50 40100229   3fffffa0:  3fffdad0 00000000 3ffeed50 402088e5

khoam · Answer

This usually happens when a program simultaneously uses asynchronous web server together with another library running in synchronous mode after TCP or UDP. . It would be good if you could show how you 'linked' this, particularly in the loop(). Somewhat excuses it, given that after a Soft WDT Reset there is rubbish left in RAM.

oskar777 · Answer

I had a similar problem with the DHT as for the ESP-7 I selected the wrong amount of memory. Sometimes it is also a power supply problem.

sq9etc · Answer

Code: main.cpp Code: C / C++Log in, to see the code WiFi.h Code: C / C++Log in, to see the code WiFi.cpp Code: C / C++Log in, to see the code . I also do ESP.reset() there.

khoam · Answer

I suggest the following modification in loop():

Log in, to see the code

.

sq9etc wrote:
I also do ESP.reset() there.

.
Better to use ESP.restart() - "cleaner" form of restart, closes network connections correctly, leaves no "junk" in registers.

What do the RAM occupancy statistics look like after compilation?

sq9etc · Answer

. 36 %. What can be done so that this compilation message window does not close by itself in Atom? It's difficult to see this memory occupation, because it closes immediately. Added after 9 [hours] 5 [minutes]: .yield() didn't help. I will still see with replacing ESP.reset() with ESP.restart().

khoam · Answer

. Did the program crash and perform a Soft WTD Reset? Or did the program not resume correctly after forcing ESP.reset()? These are two different things.

sq9etc · Answer

. I don't know that, because I didn't have the bug plugged in. The effect was that after a while it stopped reading DHT22 as before. I can only suspect that the cause was the same, i.e. Soft WDT Reset.

khoam · Answer

. However, I suggest you do this. Otherwise solving this problem will be shooting blindly. Maybe it will work .

sq9etc · Answer

After the changes:
-adding yield() where you suggested,
-replacing ESP.reset() to ESP.restart(),

is the same, ie:
-the soft WDT reset occurs,
-after the above it is not possible to get along with the DHT22, ESP.restart() does not help for lack of communication with the sensor.

khoam · Answer

. Also after the last temperature and humidity values have been correctly displayed (vide post #10)? After what time did this Soft WDT Reset occur?

sq9etc · Answer

. Exactly like this. . First time after 1h 18m of operation, second time after almost 4 hours of correct operation.

khoam · Answer

OK, that leaves one point to be clarified. I refer to the first code from post #13.
What specifically did you want to achieve by using the variables dHTReadingErrorsCount and prevDHTReadingErrorsCount ? On what state of these variables did you want to make the circuit reset dependent and in what situation?
What I see in the code is

sq9etc · Answer

. After three failed attempts to read the sensor, a reset is to be performed. With that said, if the temperature and humidity fail to be read in one cycle then I count this as one error. Therefore I entered two variables and incremented dHTReadingErrorsCount when reading the humidity, only when I failed to do so when reading the temperature. Hence the condition: Code: C / C++Log in, to see the code .

krzbor · Answer

I had a program on the ESP that sometimes rebooted (several times a day). The ESP was working with the SIM800. I decided that interference from GSM was the culprit. However, I had to tweak the program and the reboots were almost all the time. Eventually I determined that the problem was due to returning 'String' as the result of a function - it should work, but it didn't. I solved the problem by stopping the function returning the String value - the String is now passed to the function by reference and everything started working. There is a processor function in your code that returns a String. Perhaps the same problem as mine is also occurring?

khoam · Answer

Regardless of how long a period of time they occurred? Actually returning the entire String object through a function is not good practice. The problem is that the function send_P() requires a callback of type AwsTemplateProcessor :Code: C / C++Log in, to see the code Type AwsTemplateProcessor is defined as:Code: C / C++Log in, to see the code so you cannot substitute a callback function of a type other than String(const String&) . Multiple memory allocations for the String object returned by the function processor () can be avoided by defining a global variable of type String with a reservation of the appropriate buffer length using String.reserve() . This variable would be modified inside the processor() function and returned by that function - so no new String variable would be created each time for the send_P() function call. You could also use send() instead of send_P() and pass the String variable modified by processor() directly. Code: C / C++Log in, to see the code .

krzbor · Answer

Indeed, I hadn't noticed that the function was a callback. My experience with the String object was that if a function returns this object and it is assigned to a global variable, it is OK (this is how I have it in other projects). The problem arose when the result of a function returning a String was stored in another function in a local variable - in other words, stack handling came into play. Since we have a callback here, this situation also occurs.

khoam · Answer

@krzbor For me the best way to use the String class is to use the std::string class from the C++ standard library Fortunately in the case of the ESP8266 this library is available. The String class in the HAL for ESP8266 has been rewritten from the AVR version of the HAL and this is, in my opinion, a gigantic misunderstanding.

sq9etc · Answer

. An apt point, although in my case when the sensor stopped reading, it was on amen. Added after 4 [minutes]: . I replaced Send_P with Send, but nothing changed, i.e. after tens of minutes the sensor stopped responding. I commented out the part of the code responsible for retrieving and converting the time to text. Instead, I display myself the number of readings since the module started. At the moment there are 5080 readings, which means everything has been working for more than 14 hours. I continue to have three variables displayed as I had. So that doesn't look like some kind of string problem to me.

khoam · Answer

. This can happen, but I think such a meter should be reset after a certain period of time when there are no errors - erroneous readings can also be due to temporary disturbances beyond your control. On the other hand, when it actually stops reading the sensor, the next 3 erroneous readings will come out anyway. It would also be good to check if there are any memory leaks during operation. You can use the function getFreeHeap (), which returns (as a uint32_t) the amount of available memory on the heap. Using the function:Code: C / C++Log in, to see the code In loop() you can periodically send information to Serial.

sq9etc · Answer

I debugged a piece of code converting time from a uint32_t type variable to a text string, and in this form the program ran for over 3 days.
In the original version, quickly put together from the two, which I presented on the listing, there was one uncool thing. Namely, the time server was queried as often as the sensor, i.e. every 10 seconds.
I have now changed this so that the synchronisation occurs once a day after midnight according to winter time. So far it has worked since evening. I hope that this way it will already work stably for a long time. I wonder what the time divergence will be at the end of the day. I increment the time myself every sensor reading, i.e. every 10 s.

ESP8266 (ESP-07), DHT22, web server - After some time, the page does not display.

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