Design of intelligent remote control based on HID specification 1

USB (Universal Serial Bus) has the advantages of high speed, low cost, low power consumption, plug and play, and easy use and maintenance. With the gradual expansion of USB application areas, USB devices are now not only the standard input/output for computers to connect to peripheral devices, but also the standard input/output for smart TVs to connect to peripheral devices. HID is the abbreviation of Human Interface Devices, which is the earliest device class proposed and supported in the USB protocol. It is also the most widely used type of USB device. Typical HID devices include keyboards and mice. The USB serial bus specification specifically defines the HID specification. As long as the device complies with the HID specification, it is a HID device. The operating system comes with a HID driver, and users do not need to develop a very troublesome driver, which enables HID devices to establish communication with the operating system conveniently and quickly.

These advantages make HID devices more and more widely used in the field of smart TVs. This paper studies the design and implementation of a six-axis somatosensory game controller based on the HID specification for use in smart remote controls.

1 Working Principle

The smart remote control consists of two parts: the remote control and the RF receiver (Dongle). The remote control and the Dongle use the RF communication protocol to communicate; the Dongle is connected to the TV through the USB interface, and they communicate with each other through the USB protocol. According to the HID specification, a HID somatosensory game controller with input and output functions is simulated on the Dongle side, and communicates with the TV through the USB protocol, thus combining the remote control and the somatosensory game controller into one.

After the Dongle and the remote controller are successfully paired, communication is established between them. The on and off of the somatosensory game controller function in the remote controller is mainly realized through the feedback information of the TV. When the somatosensory switch key on the remote controller is pressed, the TV receives the information and immediately sends feedback information, so that the somatosensory switch indicator on the remote controller is on, and the somatosensory game controller function is turned on. Users can use the remote controller to experience somatosensory games. The TV will call the sensor module, vibration module, and Audio module in the remote controller according to the progress of the game to realize the interaction between the remote controller and the TV; when the somatosensory switch key on the remote controller is pressed again, the TV sends feedback information to turn off the somatosensory switch indicator on the remote controller, and the somatosensory game controller function is turned off.

The operation mode of the somatosensory game controller is mainly buttons and special actions. In this system, the buttons required by the somatosensory game controller are reused with the buttons of the remote control itself, and the data of special actions are converted into corresponding radio frequency key values. When there is a special action operation, it is sent out in the form of button key values. In addition, the special action function of the somatosensory game controller can be used to operate the TV part of the smart TV. In the somatosensory game controller mode, the remote control detects four actions of swinging left and right and swinging forward once or twice by calculating the data of the sensor, which can be used to switch pictures, music, etc. For example, swinging to the right is the next song, swinging to the left is the previous song, swinging forward is to pause the play, and swinging forward twice quickly is to exit.

2 System composition

2.1 Hardware System

Smart remote controllers have many functions, and this paper mainly studies the design and implementation of the somatosensory game controller function. The chips involved are mainly six-axis sensors, three-axis accelerometers (G-Sensor) and three-axis gyroscopes (Gyro) and MCUs. The accelerometer used is ADXL345, the gyroscope is IMU3000, and the MCU is IA2E. The MCU used on the dongle end is also IA2E.

2.1.1 ADXL345, IMU3000 and IA2E Performance Overview

The ADXL345 is a small, thin, ultra-low power, three-axis accelerometer with high resolution (13 bits) and a measurement range of ±16 g. Accessible via SPI (3-wire or 4-wire) or I2C digital interfaces, the ADXL345 is ideal for mobile devices. It can measure static gravity acceleration in tilt detection applications, as well as dynamic acceleration caused by motion or shock. Its high resolution (3.9 mg/LSB) enables measurement of tilt angle changes of less than 1.0°.

The IMU-3000 has a built-in three-axis gyroscope and a digital motion processing hardware acceleration engine, and has a second I2C interface to connect an external digital accelerator to execute a complete six-axis fusion algorithm. At the application level, linear and rotational movements are merged into a single data stream. Through the integrated fusion algorithm output, the IMU-3000 can reduce the intensive motion processing calculations of the system's main processor, without the need to frequently read motion sensing data, making it a low-cost, low-power microprocessor.

IA2E is a wireless audio transceiver chip from SYNIC, which includes a wireless RF transceiver module and a USB interface module. Its USB module includes a control endpoint, two synchronization endpoints and a bidirectional interrupt endpoint. It has very strong RF anti-interference characteristics. It can be connected to computers, TVs, MP3 and other devices through I2S, USB and other interfaces without any software support.

2.1.2 Hardware System Design

In terms of system design, the remote control and six-axis sensor are two separate modules. The advantage of this is that the sensor module does not affect other functions of the remote control.

This paper mainly introduces the communication method between the six-axis sensor module and MCU and the hardware system design of the Dongle end module.

First, the communication method between the sensor module and the MCU is introduced. They communicate with each other through a simple I2C communication protocol. The block diagram of the remote control functional module of the intelligent remote control with somatosensory game controller function is shown in Figure 1.

Figure 1: Block diagram of the remote control functional modules

The circuit connection between the sensor module and the MCU is shown in Figure 2. Since the sensor module requires a 3.3 V power supply, and the battery on the remote control circuit board is 5 V, a voltage conversion circuit is also required. The G-sensor in the sensor module generates acceleration data in the X-axis, Y-axis and Z-axis directions, and the Gyro generates angular velocity data in the X-axis, Y-axis and Z-axis directions. The MCU continuously polls the sensor module through the I2C bus to obtain this data, analyzes and organizes this data into 8-byte data packets, and then packages and sends it to the Dongle end using the 2.4 GHz radio frequency communication protocol.

Figure 2 Circuit diagram of the connection between the sensor and the MCU

The dongle end transmits data with the remote control end through the RF transceiver module, and transmits data with the TV through the USB bus. The hardware circuit of the dongle end module is relatively simple. The functional module block diagram is shown in Figure 3. The single-chip microcomputer IA2E is used as its MCU. Since the IA2E contains the RF transceiver module and the USB interface module, only one MCU is needed. IA2E integrates the underlying protocol in USB communication, has a trouble-free built-in firmware mode and a flexible external firmware mode. It is only responsible for data exchange, so the single-chip microcomputer program design is very simple. In addition, the LED light circuit module can be designed on the dongle end, which is not only beautiful, but also can assist the software to better realize the function of the somatosensory game controller. It can also be used to identify the working status of the TV and ensure that the dongle end responds correctly.

Figure 3 Dongle end functional module block diagram