Use this forum to chat about hardware specific topics for the ESP8266 (peripherals, memory, clocks, JTAG, programming)
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By HermannSW
#19332 Hi,

after some help on Github I was able to flash and use my ESP8266-01 via USB2TTL connector (switch at 3V3), see:

Now I tried the same cabling with ESP8266-12 and got continuous resets (seen in clear via minicom @115200).
I measured exactly 3.00V between GND and VCC on ESP8266-12 which seems to be too low.

Next I added LD33V into the mix and switched USB2TTL to 5V, resulting in 3.28V between GND and VCC on ESP8266-12, again with continuous resets.

Finally I removed LD33V and directly used USB2TTL with switch at 5V, resulting in 4.88V between GND and VCC on ESP8266-12, and this time its working?!?!?

Now I am not sure whether running ESP8266-12 at 4.88V over USB port is a good idea, thoughts?

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User avatar
By cal
#19335 Moin,

didn't used my esp 8266-12 yet but remembered something.
Google to the rescue:

Note that GPIO15 must be grounded. That fact was not stated in much the information available on-line regarding this module. The unit will simply not work without this connection. I hope this saves someone from the initial grief I went through prior to properly configuring GPIO15.

If my single intelligence fails I can still hope for Collective intelligence. :lol:

User avatar
By HermannSW
#19336 Thanks, but connecting GPIO15 to GND resulted in continuous resets again.

But I realized that even my 5V switch USB2TTL did not work most times, and I felt uncomfortable with 4.88V anyway.

The article you provided gave me the clue what is really needed, a reliable 3.3V power source.
Since I have none I just used two fresh AA batteries giving 3.32V.
And I did powercycle this setup again and again and it comes back cleanly with RST message in minicom each time.
I did not connect GPIO15 and it works, not sure whether GPIO15 really is needed for device to work.