ESP8266 Community Forum

- Tue Dec 20, 2016 7:34 pm #59769 2.96V is kind of low. I'm assuming you get about that when you measure from Vcc to Gnd. Batteries are not my first choice. You can get voltage drops, spikes, due to the internal and series resistance. If your batteries are close to 3 volts then they probably are too low.

A picture of your setup as you use it might help to tell you if you are doing anything wrong. What kind of bypass capacitors are you using? How short are the connecting wires. D15 needs to be grounded but it is best to have a resistor doing that and not a low resistance. 10K is typically used. The concern I have is that the module can try putting out a high on that pin and if you have it grounded it will draw too much current and that can affect your supply, along with not being good for the port driver circuit.

These modules are not very forgiving.

- Tue Dec 20, 2016 7:35 pm #59770 see this topic
http://www.esp8266.com/viewtopic.php?f=13&t=1380&e=0

you are missing reset button and a capacitor on reset pin connected to GND, now i'm not sure is C necessary for 12F, but for 12 it is .

- Wed Dec 21, 2016 1:38 pm #59794

2.96V is kind of low. I'm assuming you get about that when you measure from Vcc to Gnd. Batteries are not my first choice. You can get voltage drops, spikes, due to the internal and series resistance. If your batteries are close to 3 volts then they probably are too low.

Actually i think 2.96V should be more then enough, the other ESPs i have even flash at 2.27V! Always had problems when powering them with 3.3V from the USB-Serial Converter. I think because of not enough current. This one, that doesnt want to flash, does start an AP wenn powered and seems to run fine. So i think the power supply cant be the reason for the problem.
But to rule out that it has something to do with power supply i tried it again today with an external powersupply with 3.3V and its still the same. Doesnt want to boot. Also the same when powered from the serial converter.

Strange thing i noticed is that it doesnt start the AP when GND of the serial adapter isnt connected to the ESP but RX and TX are. Instead the led is on the whole time.

Ok, then i followed what shinobi said and connected Reset to 3.3V (it already had 3.3V without that direct connection, and from what i read, this is wright?). Pushbutton between GND and Reset and nothing.
When i release the button, the ESP just boots normal and starts the AP.

Then i did read the linked thread and there i saw that i should connect GPIO2 to VCC and so i did.
Now the led stays off but instead of going to flash mode after Reset button push it just starts the AP.

I can post a picture of the setup later, but basically it looks like on the photo on the beginning of this thread with only 4 cables connected. VCC, GND, RX and TX. On the photo theres a wrong resistor, now it is 9.1K because i didnt have any 10K left.

Im starting to think that i should just throw this one away and work with the others that behave like expected. But im so curious why this one doesnt want to flash but succesfully starts an AP when powered.
Oh it also doesnt react on AT commands, no matter what baud rate.
Its just under 2€ that i would loose but i live in fear the next time i order some ESPs, the whole batch will behave like that.

Thank you both for your help!

Edit: i totally overlooked the capacitor part or confused it with resistor on first reading, will try that! Thanks!
Edit2: i soldered an 10uF capacitor between GND and RST but nothing changed. Theres a realy small delay now when releasing the reset button or powering on but it just blinks two times and starts the AP.
It behaves exactly like one of the working ESPs when GPIO0 isnt grounded, i just tested. But GPIO0 is grounded or at least the pinhole. Can i somehow check if its realy grounded without measuring directly on the ESP chip? Because my measuring tips are way to big.