I am having a very weird and frustrating issue with this ESP01. I am creating a shield on protoboard, and everything checks out as far as I can tell. I am using a 3.3v voltage divider (1k and 2.2k) from arduino TX to ESP RX.

When I connect the ESP straight to the arduino Mega 2560, it works fine. When I connect the ESP to my protoboard, the blue led stays lit. Now here's he weird part.

I broke out the protoboard header with jumpers to the ESP, 3.3v to vcc and ch_pd, gnd to gnd in my header. Bypassing the logic voltage divider on my protoboard results in a working ESP8266.

While still powered up, I moved the Tx/Rx to the header, through the voltage divider, and it still works! But when I disconnect USB from the Arduino, then reconnect, the blue led stays lit, until I bypass the voltage divider, connect to the ESP, then connect back to the divider.

I am currently testing my code with a simple serial relay sketch, ESP on Serial3. I have nothing else connected to ESP besides vcc, ch_pd, gnd, tx and Rx. I am connecting to the arduino and ESP on 115200 baud. The ESP replies without garbage on 115200 when connected straight to Serial3 rx/tx

I thought insufficient power may have been an issue, using the mega's 3.3v for vcc, so I built a voltage regulator circuit converting a 9v battery to 3.3v (well 3.75, using an LM317T with R1=330ohm/R2=660ohm because it's what I had on hand) and there was no change in performance, besides the LEDs being slightly brighter. The ESP still functioned with RX/TX straight to the mega while connected to the 3.75v supply.

I know pics would help a lot, and I can post some later tonight after work. My wife, sensing my frustration, told me to set everything down and go to work so I wouldn't break anything, so I am asking around for possible fixes for when I get home.

I appreciate any and all replies, and will provide any necessary clarification.

Thanks, Vl4d

  • Just a couple of silly questions, but I'm not very much into ESP. 1) when is the LED supposed to turn off? 2) you put the voltage divider only on the ESP RX terminal (i.e. on the arduino TX), right?
    – frarugi87
    Commented Jan 11, 2017 at 8:14

2 Answers 2


A wiring diagram would help.

Also, measure the 3.3v regulator's output, especially under load; 9v batteries are best in low-drain long-life applications like smoke detectors. Another supply, perhaps Arduino's 5v supply, might be a better source for the 3.3v regulator.


I would also check the ground on the components. All of the ground pins need to be connected together. IC's get flakey with grounding issues.

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