Serial port debugging

Caution

In Firefly-RK3128 development board, pins of the debug uart2 port are
multiplexed with TF card interface, making them mutual exclusive. That
is to say, if uart2 port is in used, TF card must be plugin out, and
if TF card is in use, the uart2 port cannot be connected.

Purchase the adapter

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

CP2104

PL2303

CH340

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, no need to connect.

Black: GND，Ground, connect to GND pin of the board.

White: TXD，Transmit，connect to TX pin of the board.

Green: RXD，Receive, connect to RX pin of the board.

Connection parameters

The following serial port parameters are used by the Firefly-RK3128:

Baud rate: 115200

Data bit: 8

Stop bit: 1

Parity check: none

Flow control: none

Serial port debugging is used on Windows

Install the driver

Download the driver and install it:

CP2104

CH340 [1]

PL2303 [2]

If PL2303 does not works under Win8, please find drivers with version
3.3.5.122 or before.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:

Install software

Under Windows, the common softwares with serial port support are putty
and SecureCRT. Putty is open source software. We give a brief
introduction here. The use of SecureCRT is similar.Download putty from

[3]

 .We recommend to download putty.zip, which contains other useful
utilities.Extract and run "PUTTY.exe".

Select "Connection type" to "Serial".

Modify "Serial line" to the COM port found in the device manager.

Set "Speed" to 115200.

Click "Open" button.


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

Messages above say that "Ctrl-a" is the escape key. Pressing "Ctrl-a
Ctrl-q" can quit the terminal. Besides "Ctrl-q", there are several
control commands frequently used:

Ctrl-u : increase baud rate

Ctrl-d : decrease baud rate

Ctrl-f : cycle through flow controls (RTS/CTS, XON/XOFF,  and none).

Ctrl-y : cycle through parity check (even, odd and none).

Ctrl-b : cycle throught data bit (5, 6, 7, 8).

Ctrl-c : toggle local echo.

Ctrl-v : show program options (like baud rate, data bits, etc).