[AVR] ESP8266 response problem

[agreatstar]

I have an ESP8266 which I have interfaced with atmega16L, powered both through LM1117 (3.3V). I have tested the Tx-RX of my board/controller using a CP2102 USB module that I have and it works fine. I have also tested my ESP8266 through it and that too works. If I connect this USB module Dout to board, board TX to ESP8266, and output of ESP8266 again to DIN of USB module(forming a triangular topology), and send AT commands to ESP, I receive OK response on my PC terminal. But if I connect both Tx-Rx of ESP8266 to atmega, the output response of 8266 is garbled. The same program works for triangular topology mentioned above. SO my doubt is, is there a problem in direcctly connecting Tx-Rx pins of ESP to atmega? I have even tried inserting resistances in rage of 330ohms to 1K instead of direct connections. Has anybody faced a similar problem?

 

[D.A.(Tony)Stewart]

Assuming you correct polarity, how does signal look on scope? Have you tried twisted pair? Active terminator? CM choke?

 

[agreatstar]

I do not have CROs/DSOs. Current flowing through RxD Pin is less than 6mA(measured by Digital Multimeter). When I display the response received by Atmega on LCD, it is always 3 character long(which should actaully be 4 character long 'O K Cr Lf', always ending with '10' but the first two characters are random.

 

[D.A.(Tony)Stewart]

Have you verified all UART settings match?

 

[agreatstar]

Yes. In fact everything works in triangular topology at baud rate(9600). My Board sends AT to ESP, ESP responds with OK on PC terminal, and PC terminal sends OK to board which happily displays it on LCD. This simply stops working if I connect Tx of ESP(which was previously connected to USB to serial) to Rx of board.

 

[anandpv2009]

So problem is with your RX program. Post RX part of your program.