Recently, I've been attempting to build an anti-collision detection system for uses in a car. I bought several nodeMCU units and wil use one as a WiFi hub.

In the course of experimenting, I broke off the micro-USB connectors of two of the units. I have since purchased a hot glue gun and glued the other two down.

The problem is programming without a USB connector. I've read elsewhere, a USB-to-serial adapter/converter can be used. The units are common and feature the FTD232RL chip with the power jumper set to 3.3V. I have several. What I've read states that the FLASH button is held down while the RESET button is "tapped." This establishes bootloader mode.

I'm not sure what I'm doing wrong, but this doesn't work for me. One of the two USB-less units contains a program that runs whenever I plug it in. That unit has a 5v power supply soldered to the Vin/GND pins. After trying to follow the steps, the original programs still runs when the unit is plugged in.

The Arduino IDE compiler attempts to connect to the unit via a Windows COM port but times out. When I hold the FLASH button down and push the RESET button, I then release the FLASH button. There is a quick blip of the blue LED, then the LED comes on and stays on for about 10-15 seconds. Is this to be expected?

I also tried with the other USB-less unit which has a couple of wire leads soldered to the ESP chip to replace a broken FLASH button. The same thing happens.

Any ideas? Am I doing this correctly? I've read this post:

How to program an ESP8266 without a USB port

Thank you.

This is the wiring setup: ESP USB2Serial

Tx / Rx

Rx / Tx

Vin / 5V


UPDATE: Apr 20; I've disvcovered several of my cables are not functioning as exprected. Fortunately, three are.

  • 2
    Do you see the ESP8266 boot messages on the serial connection? You may need a strange baud rate (74880).
    – Majenko
    Apr 19 at 17:53
  • I don't understand how you power the board. If the USB socket is broken and you want to supply the ESP with the 3.3V from the external programmer, you need to connect it to the 3.3V. If you power it with external 5V don't connect the 3.3V of the programmer if it's set to 3.3V.
    – Sim Son
    Apr 19 at 18:12
  • I supply the NodeMCU with 5V from a wall plug/power supply applied to 'Vin.'. The USB-to-sewrial gets power from the USB port on that board.
    – Jim Julian
    Apr 19 at 22:36

1 Answer 1


I did some checking and discovered some of my cables are not suitable for data transfers. They seem to work for charging. Three cables worked with the ESP8266s. These calbles were used to re-program all ESP8266s/NodeCMUs, even the ones without USB connectors. The one thing the failing cables had in common was their thiness. The nworking cables were heavier and longer.

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