Serial debug

USB-to-serial adapter is the abbreviation of USB-to-serial TTL adapter.

Debugging using RS232 serial port

You can use an RS232 to USB adapter to connect AIO-1684JD4 to a PC for serial port debugging:


Serial parameter configuration

Core-1684JD4 uses the following serial port parameters:

  • Baud rate: 115200

  • Data bits: 8

  • Stop bit: 1

  • Parity: none

  • Flow Control: None

Using serial port debugging on Windows

On Windows, putty or SecureCRT is generally used. Among them, we recommend using the free version of MobaXterm. This is a powerful terminal software, which is introduced here. The usage of other software is similar.

Go here download MobaXterm:

  1. Select session as Serial.

  2. Modify Serial port to the COM port found in Device Manager.

  3. Set Speed (bsp) to 115200.

  4. Click the OK button.

_images/debug_set_MobaXterm1.PNG _images/debug_set_MobaXterm2.PNG

Serial debugging on Linux

There are several options available on Linux:

  • minicom

  • picocom

  • kermit

The following will introduce the use of minicom.

Install minicom:

sudo apt-get install minicom

After connecting the serial cable, see what the serial device file is. The following example is /dev/ttyUSB0:

$ ls /dev/ttyUSB*


$ sudo minicom
Welcome to minicom 2.7
Compiled on Jan  1 2014, 17:13:19.
Port /dev/ttyUSB0, 15:57:00
Press CTRL-A Z for help on special keys

The above prompt CTRL-A Z is the escape key, press Ctrl-a and then z to bring up the menu:

                          Minicom Command Summary                      |
  |                                                                    |
  |              Commands can be called by CTRL-A <key>                |
  |                                                                    |
  |               Main Functions                  Other Functions      |
  |                                                                    |
  | Dialing directory..D  run script (Go)....G | Clear Screen.......C  |
  | Send files.........S  Receive files......R | cOnfigure Minicom..O  |
  | comm Parameters....P  Add linefeed.......A | Suspend minicom....J  |
  | Capture on/off.....L  Hangup.............H | eXit and reset.....X  |
  | send break.........F  initialize Modem...M | Quit with no reset.Q  |
  | Terminal settings..T  run Kermit.........K | Cursor key mode....I  |
  | lineWrap on/off....W  local Echo on/off..E | Help screen........Z  |
  | Paste file.........Y  Timestamp toggle...N | scroll Back........B  |
  | Add Carriage Ret...U                                               |
  |                                                                    |
  |             Select function or press Enter for none.               |

Press O according to the prompt to enter the setting interface, as follows:

           | Filenames and paths      |
           | File transfer protocols  |
           | Serial port setup        |
           | Modem and dialing        |
           | Screen and keyboard      |
           | Save setup as dfl        |
           | Save setup as..          |
           | Exit                     |

Move the cursor to “Serial port setup”, press enter to enter the serial port setup interface, then enter the letters indicated above, select the corresponding option, and set as follows:

   | A -    Serial Device      : /dev/ttyUSB0                              |
   | B - Lockfile Location     : /var/lock                                 |
   | C -   Callin Program      :                                           |
   | D -  Callout Program      :                                           |
   | E -    Bps/Par/Bits       : 115200 8N1                                |
   | F - Hardware Flow Control : No                                        |
   | G - Software Flow Control : No                                        |
   |                                                                       |
   |    Change which setting?                                              |

Note: Hardware Flow Control and Software Flow Control must be set to No, otherwise it may result in failure to input.

After the setup is complete, go back to the previous menu and select Save setup as dfl to save it as the default configuration, which will be used by default in the future.

Debugging using DEBUG port

If you want to develop U-Boot or kernel, you need to use the DEBUG port for debugging. The operation is the same as that of RS232 debugging, but you need to pay attention to the adapter and its driver.

Optional adapter

There are many USB-to-serial adapters on the online store, which are divided into the following types according to the chip:

Serial port Maximum baud rate Recommended or not Evaluation Purchase link
CP2104 2Mbps Recommended Support high baud rate communication, good stability Durable Click to buy
CH340 2Mbps Not recommended In actual use, it is found that the actual baud rate of many CH340s on the market cannot reach 1.5 Mbps
PL2303 1.2Mbps Not recommended The maximum baud rate cannot reach 1.5Mbps

Generally speaking, adapters using CH340 chips have relatively stable performance and are more expensive.

Note: The default baud rate for Core-1684JD4 is 115200.

Hardware connection

USB to Serial adapter with four pins:

  • 3.3V power supply (NC), no connection required

  • GND, the ground wire of the serial port, connect to the GND pin of the serial port of the development board

  • TXD, the output line of the serial port, connected to the TX pin of the serial port of the development board

  • RXD, the input line of the serial port, connect to the RX pin of the serial port of the development board

Note: If you encounter the problem that TX and RX cannot be input and output when using other serial adapters, you can try to reverse the connection of TX and RX.

AIO-1684JD4 DEBUG port:


Install driver

Download the driver and install:

If you install the CP210X driver from the official website on the Windows system, use tools such as PUTTY or SecureCRT to set the serial port baud rate to 115200. If the setting cannot be set or is invalid, you can download the old version driver.

After inserting the adapter, the system will prompt to discover new hardware and initialize it, and then you can find the corresponding COM port in the device manager: