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68 lines
2.9 KiB
Plaintext
68 lines
2.9 KiB
Plaintext
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The ESP-IDF has interrupt watchdogs and task watchdogs. Normally on
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each core there is a very low prio idle task (IDLE0, ILDE1) that feeds
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the watchdog (an internal timer) and if that timer expires a
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reboot/reset happens. This thought to enure that even the lowest prio
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tasks get run ever.
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Now enter the Arduino IDE generated task loop(). When there are two cores,
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loop() is run on core1. If loop runs continiously, IDLE1 is never run and
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triggers the watchdog. It is said that this can be previented by one
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of the following:
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1. Call delay(X) with big enough X
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2. Call yield()
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While the delay() method works, big enough X to run idle seem to be in
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the ms range and there are definitely applications that can not accept
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a several ms long pause in loop().
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The yield() method does not work because it only seems not to yield to
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a low prio task like IDLE1 in all circumstances.
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Then the makers of the Arduino IDE did get the brilliant idea to
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disable that IDLE1 calls the watchdog. Then loop() can spin on core1
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and other tasks (like wifi or interrupts or whatever) can run on core0
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and are watched by the IDLE0 watchdog. All swell and well. Almost.
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Enter: SINGLE CORE ESP32
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As the IDLE0 watchdog is not disabled it will fire when loop() runs on
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core0. The next idea is to feed the watchdog from loop() just
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alongside the yield. There is a function called esp_task_wdt_feed(),
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so can that be used to feed the watchdog? Yes and no. While it
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will feed the watchdog, there is as well as check in the ESP-IDF
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that the watchdog is fed from ALL tasks that should feed it. So
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if the setup is that IDLE0 should feed the watchdog, we can not
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get away by calling esp_task_wdt_feed() from loop(). BUMMER!
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But there seems to be a way around this. The watchdog is implemented
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by low level timers/counters and these are accessible. So we can feed
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the dog behind the back of the ESP-IDF:
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#include "soc/timer_group_struct.h"
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#include "soc/timer_group_reg.h"
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void feedTheDog(){
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// feed dog 0
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TIMERG0.wdt_wprotect=TIMG_WDT_WKEY_VALUE; // write enable
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TIMERG0.wdt_feed=1; // feed dog
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TIMERG0.wdt_wprotect=0; // write protect
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// feed dog 1
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TIMERG1.wdt_wprotect=TIMG_WDT_WKEY_VALUE; // write enable
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TIMERG1.wdt_feed=1; // feed dog
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TIMERG1.wdt_wprotect=0; // write protect
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}
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As I do not have a single core ESP32 I tested this by enabling the
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IDLE1 watchdog (which normally is disabled) and checking that I
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do get watchdog resets. Then I call feedTheDog() from loop()
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and the resets disappear. So I guess the feeding operation is
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successful. For a single core ESP32 of course only dog0 has
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to be fed.
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Feed dog directly behind back of the ESP-IDF routines:
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https://forum.arduino.cc/t/esp32-a-better-way-than-vtaskdelay-to-get-around-watchdog-crash/596889/13
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Disable/Endable WDT code:
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https://github.com/espressif/arduino-esp32/commit/b8f8502f
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Get/set taskid on cores:
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https://techtutorialsx.com/2017/05/09/esp32-get-task-execution-core/
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