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Fatal exception 28 at power on?

PostPosted: Sat Dec 02, 2017 2:19 pm
by synfinatic
So I've been trying to debug this issue for hours and I thought I had the exact order of operations figured out to determine why sometimes my ESP8266 crashes at boot with:


ets Jan 8 2013,rst cause:2, boot mode:(2,0)

Fatal exception (28):
epc1=0x40100000, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000004, depc=0x00000000
Fatal exception (28):
epc1=0x40100000, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000004, depc=0x00000000
Fatal exception (28):
epc1=0x40100000, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000004, depc=0x00000000
<repeats forever>

Or while sometimes it starts just fine and will operate for hours and hours. It never seems to start to work and then fail. But after trying every combination, I can't seem to find any pattern. It kinda smells like a power issue, but I'm not really sure? The one thing I can say is that if it starts throwing that error on boot doing a reset of the ESP8266 does not make it go away. That at least seems to me to be a strong indicator it's not a power issue, but I'm not sure?

Here's my circuit design: https://synfin.net/misc/espdsc.pdf

The board is powered by a USB Battery Pack capable of 1A @5V.

I've tried the Arduino Exception Decoder tool and it only gives me the following translation of the above error:

0x40100000: _stext at ?? line ?

All my source code is available via: https://github.com/synfinatic/esp-dsc

Re: Fatal exception 28 at power on?

PostPosted: Sat Dec 02, 2017 4:18 pm
by btidey
GPIO15 must be low during boot to get it into run mode. This is normally done with a pull down resistor on that line (~4k7). That doesn't seem to be the case on your circuit.

Re: Fatal exception 28 at power on?

PostPosted: Sat Dec 02, 2017 4:52 pm
by synfinatic
Wow. Not sure how I missed that. Let me try that. thanks.

Re: Fatal exception 28 at power on?

PostPosted: Sat Dec 02, 2017 8:21 pm
by synfinatic
Also, I'm not pulling up GPIO2. How did this ever work? :lol: