I bought a ESP8266 module (like this). I connected the module like on the following scheme:
I use a USB to TTL converter (cp2102) that I've connected to RX&TX pins of the module. It works. It successfully transmits data in both ways when I test it with a MCU. I often use it to send debug messages to my PC from a MCU.
I use linux and CuteCom as a program for monitoring the data sent through the serial port.
I supply 3.3V to the module (as required by the manufacturer) from the cp2102 converter (it has both 5V and 3.3V outputs).
The module does not respond to any command I send to it (AT, AT+GMR, AT+RST, ATE0, etc). But it sends to the PC some data on boot (when I attach Vcc to CP_PD). Most of the data look like garbage, but at the very end I get meaningful data:
Ai-Thinker Technology Co.,Ltd. invalid
The baud rate is 115200. No parity, 8-bit characters, 1 stop bit. The full output from CuteCom:
The red LED on the module is always lightning while the power is supplied. During the boot process (approximately first 500 milliseconds) also a blue LED blinks a few times (probably due to sending that mostly-garbage data to the PC I mentioned earlier).
What have I tried?
I experimented with the resistor R1, tried: no resistor, 1k, 3k, 10k. I also tried other baud rates (1200, 2400, 4800, 9600, 19200, 38400, 57600). And tried using all the parity types, 2 stop bits and other character lengths. Nothing helped.
Why the module does not respond to any command? Hope for your help! Thanks in advance!