Serial Port

Serial Port

This section explains how to utilize the serial port on kobuki’s expansion port to driving kobuki by serial interface instead of USB.


Here are pinouts of expansion port, include serial pins. Minimum number of required pins for serial communication is three; TX, RX, and GND. Additionally EX3.3 or EX5 can be used for powering external devices, such as line transceiver.


  • RX/TX : Serial data connection (voltage level is 3.3V)
  • EX3.3/EX5 : 3.3V/1A and 5V/1A power supply
  • DI0~3 : 4 x Digital input (high: 3.3~5V, low: 0V)
  • DO0~3 : 4 x Digital output (open-drain, pull-up resistor required)
  • AI0~3 : 4 x Analog input (12bit ADC: 0~4095, 0~3.3V)
  • GND : Ground
  • EN : Used for detecting an external board (connect to external ground)



a) RS-232 Interface
The voltage level of serial port is 3.3V. To connect kobuki with standard RS-232 serial port, you should use line transceiver in the middle to convert voltage level. MAX232 chip is typical solution for it. Below diagram show simplified typical example of connections between kobuki and SBC. EX3.3 pin is used to powering line transceiver. It can be EV5 pin or external power sources from outside.


b) Logic Level Interface
To connect kobuki with serial port of MCU directly, below simplest connection diagram can be used. Serial pins of kobuki are 5V-tolerant. It accepts 3.3V and 5V voltage levels typically used by integrated circuit. Connection with power pin(EX3.3 or EX5) is optional, if you powering MCU with independant sources, such as battery, or wall adaptor.



a) C++ Driver for Embedded Linux Board, or Non-ROS System


b) Protocol Specification for Custom Embedded Board, or Non-C++ Driver



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This post was last modified by leechangyong on 2016년 3월 11일.

This article has not been revised since publication.

This post was created by 거북이 on 2015년 7월 21일.

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