ESP8266 Community Forum

- Sat Aug 22, 2015 10:36 pm #26843 Hi,

I have been trying the USB to Serial board for communicating with ESP-12E. I have voltage divided the Tx from USB-Serial board. But the communication is not successful and there was no response for "AT" command from ESP-12E. Also, I'm not sure whether the USB-Serial board gives 3.3v or 5v and whether the voltage divider is necessary. Is it necessary to divide the voltage from Tx line of the below board to 3.3v? If so, why could the ESP-12E is not responding to the "AT" command?



Thanks in advance,
Ajay.

- Mon Aug 24, 2015 10:08 am #26952 I have got my ESP12E up and running. I failed to connect GPIO15 to ground and because of that mis-connection ESP didn't respond my AT commands. While debugging I voluterily connected USB-Serial board to ESP12E without voltage divider. I'm still unknown what's the voltage level outputting from this USB-Serial board and why that it didn't blown my ESP module when I connected without voltage divider. Any explanations are still welcomed.

- Mon Aug 24, 2015 10:14 am #26953 Do you have any voltmeter handy ?
Just leaving the USB-UART floating, you can measure the HIGH level present on the TX line.
If it is above 3.3V, better add a voltage divider or some MOSFET level translator such as the following :