Editing esp (section)

===WDT- Watchdog Timer===
[https://arduino-esp8266.readthedocs.io/en/latest/boards.html#boot-messages-and-modes Boot messages and Modes]<br>

Here is a very [https://www.sigmdel.ca/michel/program/esp8266/arduino/watchdogs_en.html detailed explanation] of the Watchdog timers in the ESP8266.<br>

The ESP8266 is a little different than the standard Arduino boards in that it has the watchdog(WDT) turned on by default. If the watchdog timer isn't periodically reset then it will automatically reset your ESP8266. The watchdog is reset every time '''loop()''' runs or you call '''delay()''' or '''yield()''' but if you have blocking code like a while or for loop, then the watchdog may time out, resulting in your reset.<br>

The '''delay()''' function is blocking so this prevents other code from running while it's sitting there waiting out the delay. '''delay()''' doesn't cause WDT reset though because it automatically calls '''yield()''' to prevent that.<br>

When the ESP reboots, you get the reboot cause:
 ets Jan  8 2013,rst cause:2, boot mode:(3,7)

*Soft WDT: Cause 2
*Hardware WDT: Cause 4

;Cause for reset:
{| class="wikitable" 
|-
! Number
! Description
|-
| 0
| unknown
|-
| 1
| normal boot
|-
| 2
| reset pin
|-
| 3
| software reset
|-
| 4
| watchdog reset
|}

<br>

;Boot Mode
{| class="wikitable" 
|-
! Number
! GPIO15
! GPIO0
! GPIO2
! Mode
|-
| 0
| 0V
| 0V
| 0V
| Not valid
|-
| 1
| 0V
| 0V
| 3.3V
| Uart
|-
| 2
| 0V
| 3.3V
| 0V
| Not valid
|-
| 3
| 0V
| 3.3V
| 3.3V
| Flash
|-
| 4
| 3.3V
| 0V
| 0V
| SDIO
|-
| 5
| 3.3V
| 0V
| 3.3V
| SDIO
|-
| 6
| 3.3V
| 3.3V
| 0V
| SDIO
|-
| 7
| 3.3V
| 3.3V
| 3.3V
| SDIO
|}
<br>

The timeout for the hardware watchdog is 8.2 seconds, and 3.2 seconds for the software watchdog timeout<br>

Don't block software watchdog too long with blocking code, otherwise it will trigger hardware watchdog reset.<br>
You can reset the WDT inside your blocking code with:
 ESP.wdt_reset()
or
 yield();


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