Fig. 1-1 shows an overview of the communication system. As shown in the figure, the "robot" is controlled wirelessly via the "cradle.” The user does not need to be aware of the communication control between the robot and the cradle, as it is performed on the firmware of both devices. The user can easily control the robot wirelessly by sending the specified commands described below to the cradle, which is recognized as a USB serial device from the host PC side.
Fig. 1-1 Communication system overview
The robot and cradle are each equipped with a NiceRF RF2401F20 2.4GHz ISM band radio module. For more details about the radio module, please refer to this page (4. Wireless Communication Module ). Note that 2.4GHz band communication here is different from general-purpose standards such as the Bluetooth standard. Therefore, the host PC alone cannot connect and communicate with the robot without the cradle.
Fig. 1-2 shows the packet flow in the system. In this system, the packet sent from the host PC to the cradle is called an "Instruction Packet," and the packet sent from the cradle to the host PC is called a "Status Packet," in the packet exchange between the cradle and the host PC.
Fig.1-2 Packet flow in the whole system
After startup, the robot and the cradle continue to communicate with each other at regular intervals, and the cradle organizes the acquired robot information as Status Packets, which are sent to the host PC at a frequency of about 60 Hz. The user can control the robot by sending appropriate Instruction Packets to the Cradle based on the robot status obtained from Status Packets.
For more details on the Instruction Packet and Status Packet, see 3. Communication Packet List.
Three types of LEDs (Red LED, Green LED, and Yellow LED) are mounted on the cradle. Of these, the Green LED and Yellow LED blink in response to packet transmission and reception, allowing the user to visually check the flow of Instruction Packets and Status Packets. Specifically, the Green LED blinks when the cradle sends a Status Packet to the PC, and the Yellow LED blinks when the PC sends an Instruction Packet to the cradle.
The Red LED lights up when charging is being performed correctly for each robot.
Fig. 1-3 shows an example of communication timing between the application on the host PC, the cradle, and the robots. In this system, one control cycle is set at about 60 Hz. Therefore, control processing on the application must be kept within about 16.7 msec (*1).
<aside> <img src="/icons/info-alternate_gray.svg" alt="/icons/info-alternate_gray.svg" width="40px" /> *1 This time is sufficient to control one robot. However, as the number of control units increases, the number of Instruction Packets also increases, so care should be taken in the time required to calculate and send packets for control processing with multiple units to a group.
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Fig. 1-3 Overview of communication and timing in each element.