What is "Fatal exception (29)"?

[eyal]

I have a few esp modules. This time I use an esp-07 with a very simple test program (in lua) that repeatedly deep sleeps for 1 second.

Code: Select all

node.dsleep(1*1000000)

After a few loops (10 to 30) it stops during the wakeup and at 115200 baud I see:

Code: Select all

MEM CHECK FAIL!!!
Fatal exception (29):
epc1=0x40222768, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000044, depc=0x00000000

What is it trying to tell me? Is it the SDK or lua talking? Better yet, where is this information documented?

This was the case with SDK 0.9.5, 1.0.0 and now also with 1.0.1b1.

Thanks

[YimingLi]

Hi,

The number in the parenthese, i.e. 29 in this example, should be "exception cause" number defined by Xtensa chip core.

According to Xtensa datasheet, exception cause 29 is "Strore Prohibited Cause", a store referenced a page mapped with an attribute that does not permit stores.

Hope it will be helpful.

[kolban]

You can also use the "epc1" property to determine the instruction that caused the problem. Since this is a hex address in memory, it isn't that immediately useful, however if you use objdump to dump the address tables of the compiled application, you can figure out "pretty closely" where in your code the problem was caught.