ESP8266 Community Forum

- Tue Mar 03, 2015 5:10 am #11149 I thought I'd share my experiences in getting some ebay ESP-01 modules flashed with the latest AT firmware. I'm using Linux and esptool.py. After getting the modules into bootloader mode quite easily by tying GPIO0 to ground, I simply couldn't get esptool to connect. It kept saying "Failed to connect". I checked everything, from the traces on the board to double-checking my logic levels, and the fact that esptool's Tx made it in at proper 3.3V levels. All seemed fine, but it just wouldn't work.

At a whim, I decided to replace my USB-serial interface, and changed from my "USB BUB II" (using a FTDI 1131) to a no-name CP2102 I bought off eBay. And presto, esptool flashed on the first try.

Here's a summary of the actual connections made for flashing:
- USB module Tx --> URXD
- USB module Rx --> UTXD
- USB module ground --> GND
- external 3.3V power supply --> VCC
- GPIO2 --> VCC
- GPIO0 --> GND
- CH_PD --> 1K --> VCC
- RST --> 1K --> VCC

I'm posting this so others may benefit. If someone happens to have an idea why one serial module won't work and another would, let me know.

- Sat Apr 09, 2016 9:22 am #45173 I had same problem. I will try using CP2102