ESP8266 Community Forum

I was trying to get a delay in a program. The program kept crashing, so I reduced it to a minimal while loop and just tested that. It crashes every time.

I am running ESP8266 LuaLoader 0.87
NodeMCU 0.9.6 build 20150704 powered by Lua 5.1.4

The "Test.lua" code:============================

print("begin test")
DelayEnd = 0
while (DelayEnd == 0) do end
print("end of test")

The output: ===================

dofile(Test.lua) Sunday, January 03, 2016 12:24:33

dofile("Test.lua")
begin test
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NodeMCU 0.9.6 build 20150704 powered by Lua 5.1.4
lua: cannot open init.lua
>
Hard Restart Sunday, January 03, 2016 12:24:38

Anybody have an idea what the problem is?

The endless loop prevents that the watchdog is serviced in time. Thus it resets the chip after ~5 seconds.
You should generally avoid busy waiting loops with the nodemcu firmware. If you can't avoid them, then feed the watchdog in time.

The correct way to delay your execution is to use a tmr.alarm() callback. Anything else will just trip the watchdog, or cause the WiFi stack to fail.

Thanks, I didn't think of the watchdog timer.
How do I avoid triggering the watchdog timer? I modified the code to put some code into the wait loop, but it still crashes.

print("begin test")
DelayEnd = 0
while (DelayEnd < 10000) do
print(DelayEnd)
DelayEnd = DelayEnd + 1
end
print("end of test")

This counts to 661 before the watchdog timer triggers.
I divided the loop into a 500 count incrementing while followed by a 500 count decrementing while and the watchdog timer still triggers while counting down at 339.

print("begin test")
DelayEnd = 0
while (DelayEnd < 500) do
print(DelayEnd)
DelayEnd = DelayEnd + 1
end
while (DelayEnd > 0) do
print(DelayEnd)
DelayEnd = DelayEnd - 1
end
print("end of test")

I found tmr.wdclr() to clear the watchdog timer, now it will count to 10,000 without problems.

print("begin test")
DelayEnd = 0
while (DelayEnd < 10000) do
print(DelayEnd)
DelayEnd = DelayEnd + 1
tmr.wdclr()
end
print("end of test")

My question now is... What "resets" the watchdog timer in a normal program since I don't call tmr.wdclr()?