Serial port debugging

Purchase the adapter

There are many USB-to-serial adapters on the online store, and they have the following types according to the chips:

In general, the adapter with CH340 has stable performance and is more expensive.

Hardware connection

There are four different color of connection line for the serial-to-USB adapter:

  • Red: 3.3V power supply, the connection is not required

  • Black: GND, which is the ground wire of the serial port and is used to connect the GND pin of the serial port of development board

  • White: TXD, which is the output line of the serial port and is used to connect the TX pin of the serial port of development board

  • Green: RXD, which is the input line of the serial port and is used to connect the RX pin of the serial port of development board

Note: if you are experiencing the problems with the TX and RX that cannot be input and output using other serial port adapters, you can attempt to swap the connection between TX and RX.

Serial port connection diagram for AIO-3288C:

_images/module_serial2.jpg

Connection parameters

The following serial port parameters are used by the AIO-3288C:

  • Baud rate: 115200

  • Data bits: 8

  • Stop bits: 1

  • Parity check: None

  • Flow control: None

Serial port debugging is used on Windows

Install the driver

Download the driver and install it:

If PL2303 is not properly used on Win8, please refer to this article to use the version 3.3. 5.122 of old driver or later.

Once the adapter is plugged in, you are prompted to discover the new hardware and initialize it, then you can find the corresponding COM port in the device manager:_images/debug2.png

Install software

In general, the putty or SecureCRT is used under Windows. In which, the putty is the open source software. Here we introduce that the SecureCRT is used in a similar way to putty. You are recommended download the putty to download putty.zip here, which contains other useful tools.

After extraction, you can run the PUTTY. exe, select the Connection type as Serial, set the Serial line to the COM port seen by the device manager, and set Speed (baud rate) to 115200, and then press Open:

_images/debug3.png

Serial port debugging is used on Ubuntu

There are several options available on Ubuntu:

  • picocom

  • minicom

  • kermit

It is relatively simple to use the picocom, and next we will introduce the picocom, and other software is similar.

Install

sudo apt-get install picocom

If the serial line is connected, you can see what the serial device file is, and the following example is /dev/ttyUSB0

$ ls /dev/ttyUSB*
/dev/ttyUSB0

Run

$ picocom -b 115200 /dev/ttyUSB0
picocom v1.7

port is        : /dev/ttyUSB0
flowcontrol    : none
baudrate is    : 115200
parity is      : none
databits are   : 8
escape is      : C-a
local echo is  : no
noinit is      : no
noreset is     : no
nolock is      : no
send_cmd is    : sz -vv
receive_cmd is : rz -vv
imap is        : 
omap is        : 
emap is        : crcrlf,delbs,

Terminal ready

The above information indicates that Ctrl-a is the Escape key, and you can exit the terminal by pressing Ctrl-a Ctrl-q. In addition to Ctrl-q, there are several commonly used control commands:

  • Ctrl-u :Increase the baud rate

  • Ctrl-d :Reduce the baud rate

  • Ctrl-f :Switch the flow settings (hardware flow control RTS/ CTS, software flow control I/ O, none)

  • Ctrl-y :Switch the parity check (even, odd and none)

  • Ctrl-b : Switch the data bits (5, 6, 7, 8)

  • Ctrl-c :Switch the local-echo switch

  • Ctrl-v :Display the parameters and status of current serial port