EC200U Series - GPS NMEA and PPP Conflict on Same UART Port

IoT Modules LTE Standard Module
1

Hello Quectel Team,

I am currently working on a project using the EC200U Series 4G LTE module with a microcontroller ESP32-S3 running MicroPython.

I have successfully established a PPP connection using the main UART port. However, I am facing a conflict issue where I cannot poll GPS data while PPP is active, because both operations are competing for the same UART port.

My current setup:

  • MCU: ESP32-S3 with MicroPython
  • Module: Quectel EC200U Series
  • Main UART: Currently used for PPP internet connection
  • GPS Config: Using AT+QGPSCFG="autogps",1 and AT+QGPSCFG="nmeasrc",1

The problem: When PPP connection is active on the main UART, I cannot send AT commands like AT+QGPSGNMEA or receive NMEA sentences because the port is occupied by PPP data.

I would like to ask:

  1. Is it possible to output NMEA GPS sentences to a separate UART port (such as uart2 as shown in AT+QGPSCFG="outport" response below) so GPS runs independently from PPP?
  2. From my module, the response of AT+QGPSCFG=? shows these outport options:
+QGPSCFG: "outport",("none","uart1","uart2","usbat","usbmodem","usbnmea")

What exactly are uart1 and uart2 mapped to physically on the EC200U? Are they Main UART and Aux UART respectively?

  1. Based on the hardware design document, the EC200U has Main UART, Debug UART, and Auxiliary UART. However, the Quectel engineer previously mentioned that Auxiliary UART = Debug UART. Could you please clarify this?
  2. If CMUX is the recommended solution, could you provide a simple example or reference on how to set up CMUX on EC200U specifically for separating PPP data and GPS NMEA on the same physical UART, considering our host side is ESP32-S3 with MicroPython?

Any clarification or reference documentation would be greatly appreciated.

Thank you.

2

Dear Customer,

In PPP mode, the UART is occupied by PPP data, so AT commands and GNSS polling cannot be used on the same raw UART at the same time. If the module supports AT+QGPSCFG="outport","uart2" and the corresponding UART pins are available in the hardware design, NMEA can be output to that port independently.

Normally, uart1 refers to the main UART and uart2 refers to the secondary UART, but for EC200U the exact mapping depends on the module variant and pin multiplexing. Please check whether the UART2/Aux/Debug pins are exposed and usable in the current hardware.

If only one UART is available, the recommended method is CMUX. With CMUX, PPP and AT commands can run over different virtual channels on the same physical UART. However, the host side must support GSM 07.10 / 3GPP 27.010 multiplexing. On ESP32-S3 with MicroPython, this may require a custom CMUX implementation or driver.