espaper won't boot anymore

Question

I used the espaper kit for 3 days or so with my own server and was very happy with the battery lifetime (from 4.13 to 4.08 in 3 days).

Unfortunately the device stopped working all of a sudden and just displayed the "Device not found" screen. I attached the serial monitor and only got garbage ("{l    #l⸮rs$    cl⸮{⸮⸮⸮c⸮     # ⸮⸮r⸮    d`⸮⸮ol⸮{⸮⸮NoNb$b>"). A lot and really fast. Kinda like the output you get when resetting a normal esp8266, just a LOT more and it doesn't stop. So I tried to program again and this did work like a charm. So I guess the bootloader still works. After programming I got the following error over and over:

epc1=0x40229904, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000000, depc=0x00000000
Fatal exception (0):

After turning it off and on again I got the same garbage again.

So I tried a different programmer I had lying around with the same result: flashing worked, but exceptions and then garbage.

I now tried the following small test program but it behaves exactly the same and gives me lots of garbage. It works fine on another esp8266 I have here. So I don't think it is my environment. Especially since it happened all of a sudden and I can still flash, but get garbage only.

Any idea what else I could test?

void setup() {
  Serial.begin(115200);
  Serial.print("Setup");
}

void loop() {
  Serial.print(".");
  delay(1000);
}

Answer 1

If you are reading the exception in clear text you might have switched the baud rate of the serial monitor. Please make sure that the baud rate in the serial monitor is set to 115200. Note: I'm not talking about the baud rate of the Tools menu in the Arduino IDE, but the one in the lower right corner of the window where you see the garbage...

Comments

The exception shows only right after flashing without a reboot. The baud rate is set to 115200. I also tried setting it to 9600: Just slower garbage.
Also: In my test sketch above I explicitly set the baud rate to 115200. I also have it set in the board settings as well as in the console.

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Also tried flashing my simple test script with 9600 baud and then opening serial console with 115200 baud. Same result. Tried all baud rates in console. Nothing works. Arduino GUI actually gets unresponsive at 115200 after a short while as too much data gets transferred into the console window.
Just to make sure: This used to work (same arduino and GUI version) and still works just fine with another esp8266. I have been programming esp8266s for over 2 years now but I never had the situation that the console would output garbage at that rate and without ever stopping.

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The following thread discusses the problem in detail btw (with no solution): https://bbs.espressif.com/viewtopic.php?f=65&t=1606&sid=181336a054c19053ac49cecab7a8ffc3

So I currently believe I got a defective module here. Just in case: I only took the whole thing apart real quick in the beginning. Since then it has been in its housing so I don't see how an ESD should have occurred. Especially since it was running over night and dead in the morning.

I can try flashing firmware using esptool if you let me know how, where and what exactly.

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I will contact you by email to discuss a replacement