ESP8266 Community Forum

- Sun Aug 16, 2015 12:58 pm #26195 With 1K pullup on GPIO0, I get a single blue flash, but sketch does not run, just the line of garbage on serial monitor.

If I then ground GPIO0 and cycle the power, I get a single blue flash (nothing on serial monitor at this point) and can then upload a sketch. Remove the ground from GPIO0 (leaving 1K pullup) and cycle power, I get a single flash, garbage on serial monitor, but if I attempt sketch upload a sketch I get "warning: espcomm_sync failed/error: espcomm_open failed"

Really could do with interpreting that serial monitor garbage...

- Sun Aug 16, 2015 1:54 pm #26200 Sort of stumped - two thoughts:

I'm not sure how old the development board is, it might be worth moving to a different area (one you don't use much, if like me the far right), just incase some of the connectors are a little worn (250 mA could be to much for worn connectors).

I think your UK like me. Do you want to do a swap? I'll send you one that I know works & you send me one that doesn't. For 62p & the price of an ESP it's worth it to me to bottom this. If your code is in Arduino IDE & you post it, I'll load & test it (but will need tonight or early tomorrow as working away for a few days), if not I could just load up blink & hit the post tomorrow.

- Sun Aug 16, 2015 5:30 pm #26221 Hi, yes why not, that would be great. I knew you were in UK, "BarnabyBear" would be too much of a coincidence.

The sketch I've been trying to run is nothing more than Serial.begin(115200); in setup() and Serial.println("hello"); delay(500); in loop().

I ripped everything off the (relatively new) breadboard today, flipped it 180 degrees and put it all back together again. Exactly the same behavoir.

I'll PM you my address. Thanks again.

Paul

- Sun Aug 16, 2015 8:12 pm #26230

GPIO 2 needs the resistor as:
It needs to be floating or pulled high at boot (still being debated) but not low.

@Barnabybear, there is no such debate about this subject, it is clear since almost a year : https://github.com/esp8266/esp8266-wiki ... ot-Process

If the "debate" you're mentioning is the fight I've with someone, let make it clear here : "Leaving a pin floating is simply a BAD engineering practice. Having a pullup resistors on those pins provides a safety against ESD". Any engineers agree with that. You can read again Squonk intervention and the follow-ups here : viewtopic.php?f=6&t=4390&start=5#p25384.
The only person who does not agree have posted there too, and he is the only one who doesn't admit that "X" and "floating" are not equivalent, and the only person on the planet that says that pullups are not equivalent to "H" mentioned in the Boot process true table.
As conclusion, which can help here in this thread, both GPIO0/GPIO2 needs to be pulled-up (and GPIO15 pulled-down) to get in proper Boot mode, that's what Boot process true table stating.