LED stable,N/W registration done,Ring(calling) is also working but stop respondint simple AT command

Hello Ravi,
I have gone through all issue topics but didn’t find category and solution similar to my question so I created a new one.

In my case,

  1. LED stable and network registration done.
  2. Ring is also going on when call to number from my cell
  3. COnnection and baud rate also checked

Problem:
I am using the same module from 1 week and was working properly But now it is not responding AT(simple AT) command.
Can you help,what may be the problem?

Are you using IO level translation on the UART lines?

Yes,I am using USB-TTL(CP2102) to communicate with SIM800L module.

Thats not IO level conversion. Make sure you use something like TXS0104 or TXS0108 to convert the IO levels to 2.8V levels, If you connect 5V TTL IO signals it might keep rebooting and IO will be damaged

Thanks a lot Ravi. I got your point completely.I will check by using mentioned ICs.
Your work answer people like me is wonderful job.
Appreciated

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Can you send me schematic/app note for that means how to make connection of TXS0104 or TXS0108 with GSM800L?