new to IOT

[johnny78]

hi Guys
it my first time to work with IOT & webservers & this stuff
i have tested the Esp01 web server & used the ip address to enter a page to control an output
what i need to design an android App to control outputs & display Values ?

any idea to start with

thanks
Johnny

 

[KlausST]

there is no prove the WDT will work when the MCU hangs for unexpected reason

The unexpected hangs are the reason why they invented the WDT!
--> So be sure the WDT will work "especially" on unexpected hangs.

& yes i have my experience with this earlier

For me personally: This is a "one man´s opinion without proof".
It is way more likely that what you "experienced" was due to a different mistake. Either schematic, PCB layout, wiring, soldering, WDT setup, timing (even in SW), measurement.. or simply wrong expectation.
I personally have never seen any evidence for WDT malfunction, nor have I heard of an according silicon malfunction. If there was ... you surely would see some press releases about it since in worst case this may cause a risk of life. WDT is a security feature ... it simply HAS to work.

lets say i have my first Pic12c508A working since 2008 with WDT enabled coded in assembly & it works until now
maybe the WDT reset it when something wrong happen or not but i trust it
in case of what it does not do (the WDT)i want an external solution to solve this

It is way more likely that the power supply voltage dropped ... and the microcontroller did not work at all. In this case one needs to add "default mechanisms" to activate a safe status.
Let´s say now in this case you add your external power down RESET circuitry. This may cause the circuit to power down.... but it never can auusre to go out ouf power down ... and make the microcontroller do usueful things. A microcontroller needs a specified minimum voltage to run.

How a microcontroller behaves on low voltage, on RESET, on WDT reset is defined. Which pins and registers default to a known state, which one default to an unknown state. Pin´s often become high impedance... resulting in an unpredictable state. It may change with time, with temperature from device to device.
And it´s the job of the designer to add techniques to get a predicatble state (often simply by using pull up / down resistors).
If the designer misses this ... no external circuitry will improve the situation.

Or let the reason be a bad solder junction in the XTAL circuitry of a microcontroller. No external circuitry can make the microcontroller to RUN safely. BUT the WDT will cause a RESET ... and do what the dataheet describes in that situation.

Or let there be an overvoltage (maybe ESD, maybe on the power supply, maybe on any pin) problem causing a destruction of the silicon in a way that the microcontroller can not work as specified. Then no external circuitry can cure the microcontroller. It will stay defective. Maybe with unpredictable result. But then the root cause is not the WDT malfunction.. it is a missing (ESD) protection .. or a defective power supply, that may oscillate at a random temperature.
--> the same behaviour would be if you have an external power down circuitry.

If I had the same problem ... I would find a proof, an evidence .. and not rely on my opinion. I´d search for the root cause.
I can not say what leads you to this opinion. But I´m very sure:
--> If there was/is a WDT problem on a PIC12C508A ... then you will find plenty of discussions about it in the internet. (I did not do a search)
Maybe affected batch numbers, maybe workarounds ...

Klaus

 

[danadakk]

Not to get in the weeds (WDT not always....) :

https://www.ti.com/content/dam/videos/external-videos/en-us/9/3816841626001/6313371139112.mp4/subassets/introduction_to_wdts.pdf

http://rsim.cs.uiuc.edu/Pubs/srinivasan_isca04.pdf

https://forum.microchip.com/s/topic/a5C3l000000LuOTEA0/t208509 Latchup....

https://www.allaboutcircuits.com/technical-articles/watchdog-timers-microcontroller-timers/ Servicing failure and other....

https://www.ganssle.com/watchdogs.htm WDT space applications

Bedtime reading.


Regards, Dana.

 

[johnny78]

The unexpected hangs are the reason why they invented the WDT!
--> So be sure the WDT will work "especially" on unexpected hangs.


For me personally: This is a "one man´s opinion without proof".
It is way more likely that what you "experienced" was due to a different mistake. Either schematic, PCB layout, wiring, soldering, WDT setup, timing (even in SW), measurement.. or simply wrong expectation.
I personally have never seen any evidence for WDT malfunction, nor have I heard of an according silicon malfunction. If there was ... you surely would see some press releases about it since in worst case this may cause a risk of life. WDT is a security feature ... it simply HAS to work.


It is way more likely that the power supply voltage dropped ... and the microcontroller did not work at all. In this case one needs to add "default mechanisms" to activate a safe status.
Let´s say now in this case you add your external power down RESET circuitry. This may cause the circuit to power down.... but it never can auusre to go out ouf power down ... and make the microcontroller do usueful things. A microcontroller needs a specified minimum voltage to run.

How a microcontroller behaves on low voltage, on RESET, on WDT reset is defined. Which pins and registers default to a known state, which one default to an unknown state. Pin´s often become high impedance... resulting in an unpredictable state. It may change with time, with temperature from device to device.
And it´s the job of the designer to add techniques to get a predicatble state (often simply by using pull up / down resistors).
If the designer misses this ... no external circuitry will improve the situation.

Or let the reason be a bad solder junction in the XTAL circuitry of a microcontroller. No external circuitry can make the microcontroller to RUN safely. BUT the WDT will cause a RESET ... and do what the dataheet describes in that situation.

Or let there be an overvoltage (maybe ESD, maybe on the power supply, maybe on any pin) problem causing a destruction of the silicon in a way that the microcontroller can not work as specified. Then no external circuitry can cure the microcontroller. It will stay defective. Maybe with unpredictable result. But then the root cause is not the WDT malfunction.. it is a missing (ESD) protection .. or a defective power supply, that may oscillate at a random temperature.
--> the same behaviour would be if you have an external power down circuitry.

If I had the same problem ... I would find a proof, an evidence .. and not rely on my opinion. I´d search for the root cause.
I can not say what leads you to this opinion. But I´m very sure:
--> If there was/is a WDT problem on a PIC12C508A ... then you will find plenty of discussions about it in the internet. (I did not do a search)
Maybe affected batch numbers, maybe workarounds ...

sorry Klaus my pic12c508A is still working since 2008 as i said
but we had a discussion about my atmega328 freezing after 1 year or more thats when other of the same board is working for more than 2 years without stop & the ?WDT couldnt help & i have uploaded a video proving that the way i use the WDT is working when i cause it to reset the MCU

anyway thanks for your time but i need the full solution which its in my opinion the power reset

--- Updated Oct 4, 2024 ---

Not to get in the weeds (WDT not always....) :

https://www.ti.com/content/dam/videos/external-videos/en-us/9/3816841626001/6313371139112.mp4/subassets/introduction_to_wdts.pdf

http://rsim.cs.uiuc.edu/Pubs/srinivasan_isca04.pdf

https://forum.microchip.com/s/topic/a5C3l000000LuOTEA0/t208509 Latchup....

https://www.allaboutcircuits.com/technical-articles/watchdog-timers-microcontroller-timers/ Servicing failure and other....

https://www.ganssle.com/watchdogs.htm WDT space applications

Bedtime reading.


Regards, Dana.

oh Dana its not a bedtime reading its a whole night reading & im sorry when i had that freeze issue with my Atmega it was after 8 months & the other one was after 11 months maybe when other boards are working for more than 2 years & when i cant know what is the reason so i cant wait for testing 6 or 9 or more months when it may not happen anytime
i dont like it & i dont trust it & maybe im not that expert but in my opinion when i have another solution i prefer to use it

thanks for your time
Johnny

--- Updated Oct 4, 2024 ---

Not to get in the weeds (WDT not always....) :

thanks for the nice information
for sure im not that expert but as i said its a whole night reading but accidentally i read some of & get happy when reading this story
https://www.ganssle.com/watchdogs.htm

now i can dream of designing a control system of a spaceship
& in case of anything wrong happened i can tell them sorry my expected to do the reset WDT is not working or its me who have errors in my design & code
just turn the power off for 30 seconds & everything will b ok