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I am using Quectel EC200U in my design. This module contains three UART interfaces. The description is given below.

The module provides three UART interfaces:

The 1) main UART interface, the 2) debug UART interface, and 3) auxiliary UART interface.

The following shows their features.

  1. Main UART interface: The main UART interface supports 4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800 and 921600 bps baud rates, and the default is 115200 bps. This interface is used for data transmission and AT command communication and supports RTS and CTS hardware flow control.

  2. Debug UART interface: Only supports 921600 bps baud rate, used for the output of partial logs.

  3. Auxiliary UART Interface

May I know what is the difference between main UART interface, debug UART interface, and auxiliary UART interface?

Why we need a separate UART for debug purpose?

Why can't we use the main UART for debug purpose?

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2 Answers 2

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Why we need a separate UART for debug purpose?

For monitoring, for example.

If you check the hardware design guidelines you'll see that the aux UART is a dedicated UART module for Linux console and log outputs.

In general, a separate communication module specifically for debugging purposes can be useful. While running the code in debug mode (for testing purposes) you may want to see the contents of a register or an array or something else.

Why can't we use the main UART for debug purpose?

Because it is what it is. This is how the manufacturer has done.

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Of course the device manufacturer only knows the answer, but if you think for a moment, if you want your device to communicate with a given protocol (AT commands, modem link data with your protcol) with the main UART, then your device cannot know what data comes via modem link and what data is debug data.

Even if you make a simple MCU product, you likely want one UART for debug console, and if another UART is used for communicating with some other device, then it is reserved for that purpose.

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