Port Connection for EC20

I am using a Beaglebone black booted with SDK RTOS. I have my UART1 port pinmuxed on the GPIO pins. Will I be able to connect to the RS232 Main port using jumpers with only 3 signals (TX,RX,GND) to send AT commands??

Hi Karthik_Eswar, thanks for your question
You can use 3 signal (TX, RX, GND) jumpers to connect to the RS232 main port to send AT commands, but make sure that the level has been correctly converted (1.8v-3v-12v), thank you.

Thank you Duncan for confirming the signal lines. However, I am not sure about the voltage levels, any suggestions to make sure I am doing it right?

I even tried using USB-TTL from my windows running PC to send commands via the Qcom tool, and I have done the continuity check but I am not able to.


Hello Karthik_Eswar
If you just use the RS232 main port to send AT commands (the logic of the flying line is RX-TX, TX-RX, GND-GND), you don’t need USB-TTL. As for the level, you can refer to the attached EC20 Hardware mobile phone manual, it is recommended to use the corresponding level conversion chip as recommended in the manual, thank you.Quectel_EC20_R2.1_Hardware_Design_V1.2.pdf (1.4 MB)


I have purchased the TXS0108E voltage translator for UART communication. I am confused how to provide 1.8V for Va and how to connect the OE pin of the voltage translator?

Hello, Va 1.8V is the output voltage of the module, and the input voltage of the module is provided by the VBAT pin; the OE pin can be designed according to the reference circuit connection method:the external resistance ensures that the output is Hi-Z state during power-up or power-off .