Design of wireless USB interface transceiver based on PDIUSBD12

1 Introduction
Universal Serial Bus ( USB ) provides a new way for personal computer peripheral input and output. of Interface standard. It enables the equipment to have fast, hot-swappable, plug-and-play, and automatic configuration capabilities, and standardizes the equipment At the same time, the USB cascade star topology not only allows up to 127 external devices to be connected , but also solves resource conflicts. ,middle The traditional transceiver generally communicates with the PC via RS232 interface . If the USB interface is used instead , the wireless / wired transceiver will have many advantages of USB communication.
PDIUSBD12 is a USB device that fully complies with the USB11 specification and is optimized for performance . It is usually used in microcontroller-based Tie The device uses a module to communicate with the microcontroller through a high-speed universal parallel interface and also supports local DMA transfer. change This allows the selection of the most suitable microcontroller as the system microcontroller from among the many available microcontrollers . Allows use of existing architecture and minimizes firmware investment. This flexibility reduces development time, risk, and cost , is the fastest way to develop low-cost and efficient USB peripheral device solutions.
According to the actual situation on site, select TDX230RTMD radio and matching antenna, which can provide voice or data signals Transparent transmission, can adapt to various point-to-point and point-to-multipoint wireless data communication methods, with integrated transceiver and easy installation , simple to use, cost-effective, stable and reliable, and is widely used in remote data collection and control systems.
Combining the advantages of the above two technologies, a wireless USB interface transceiver is designed to transmit data over long distances without Line transmission.

2 Hardware Circuit Design
The overall block diagram of the hardware circuit of the wireless USB interface transceiver designed in this paper is shown in Figure 1 .
Philips ' PDIUSBD12 chip complies with USB1.1 specification and adopts 28- pin SO or TSSOP package. It can work at 3.3 ± 0.3V or 3.6 ~ 5.5V , and has internal integrated SIE and 320B FIFO buffer . ​ , transceiver, voltage adjustment circuit and termination resistor, providing a 2 MB/s parallel interface with fully autonomous local DM A achievement The chip also provides a programmable clock, Power-on reset and low voltage reset circuits. The chip provides double input and output buffers, reaching 1 MB/s in batch mode Data transfer rate, synchronous mode can also reach 1 MB/s data transfer rate.
The microcontroller MCU uses Atmel 's 89C52 . The MCU 's serial port is directly connected to the modular wireless data transmission and receiving modules RXD and TXD PDIUSBD12 is connected to the data bus of the MCU , and the interrupt pin INTN is connected to the interrupt input of the MCU . . 2 It will automatically process the data on the USB bus, write the event into its own interrupt register, and pull down INTN to notify M CU The MCU responds to the interrupt and reads the contents of the interrupt register for judgment and processing. If data is required to be sent, the data The data is sent to the modular wireless data transmission transceiver module through the serial port, and then transmitted. After receiving the data, the serial port interrupt is triggered, and the MCU responds to the interrupt and sends the data to the USB bus. , the whole system uses self-powered mode.

Figure 2 shows the interconnection diagram of an 89C52 microcontroller and a PDIUSBD12 integrated circuit . use A widely used single-chip microcontroller, software developers develop a large number of software development platforms based on it. Most electronic engineers are familiar with it. Therefore, users can use the familiar microprocessor (89C52) for core The core program is designed to use 89C52 to realize the required functions, specifically converting data signals into signals that comply with USB rules. , it is completely completed by PDIUSBD12 . In this way, we can use the rich software resources in 89C52 and USB The plug-and-play and hot-swap features of bus technology reduce the cost of developing equipment and shorten the development cycle. [page]

3. Software design
The software design mainly includes two parts: one is the MCU software on the USB device side, which mainly completes USB protocol processing and data exchange. The second is the upper management program, which is composed of the USB communication program and the user service program . The device communicates with the system through the USB communication program, and the system completes the USB protocol processing and data transmission.
3.1 MCU software design
The microcontroller control program consists of three parts: initializing the microcontroller and all peripheral circuits (including PDIUSBD12 ); Follow The tasks of the loop part are interruptible; the tasks of the read and write interrupt service routine are time-sensitive and must be executed immediately.
The communication between the MCU and PDIUSBD12 is mainly realized by the MCU sending commands and data to PDIUSBD12 . life The command words can be divided into three types: initialization command words, data flow command words and general command words. PDIUSBD12 provides various command words . The microcontroller first sends a command to the command address of PDIUSBD12 , and then sends and Therefore, you can write functions with different functions, use functions to implement various commands, and then directly call the functions. Just count.
Background D12 interrupt service program and modular wireless data transmission and reception module interrupt service program and foreground main loop program Between Data exchange is achieved through event flags and data buffers. The background interrupt service routine is triggered by an interrupt. Flags Communicate with the main module. The main module cyclically scans each flag bit and processes the corresponding flag bit. For example, the module Wireless Digital After the transceiver module receives valid data, it sends it to the serial port to trigger the serial port interrupt, and enters the modular wireless data transmission transceiver module interrupt The service program receives the data and puts it into the data buffer, then sets the UART_DATA flag and exits. When the main module finds that UART_DATA is set, it calls the writendpoint () program to send the data to the PC .
According to the USB protocol, any transfer is initiated by the host, so the 89C52 does its foreground work and waits for interrupts. First, a token packet must be sent to PDIUSBD12 . After receiving the token packet , D12 sends an interrupt to 89C52 . Enter the interrupt service routine, first read the interrupt register of D12 , determine the type of USB token packet, and then perform the corresponding operation Therefore, the 89C52 program of USB is mainly the writing of interrupt service program. In the 89C52 program of USB, various interrupt service programs must be completed. The response of the token packet, among which the more difficult to process is the Setup packet, which is mainly the programming of terminal 0. MCU software flow chart As shown in Figure 3 .

3.2 Host software design
The host computer program mainly calls four API functions . According to the host computer 's use of the USB port, use Delphi to call these four This function can realize the host computer's operation on the USB port.
Philips provides users with the driver for D12 , but users need to modify the inf file according to their own requirements. Then recompile and link in Windows DDK to generate a new driver to meet the needs of actual applications.
When writing a host application, pay attention to the operation of the host terminal and increase the data cache in the program. Philips The provided driver supports 64 B~64 kB of cache, which can effectively reduce the handshake time between the device and the host and provide High transmission speed. When compiling the program, you need to pay attention to maintaining the compiled path.

4 Conclusion
This paper combines the advantages of USB interface and wireless communication technology and applies them to multi-point temperature measurement control system to provide a reference for PC and smart It provides a fast and convenient way to exchange data between instruments.
Directly expand the USB interface technology of the single-chip microprocessor With the continuous development of USB technology, USB will be widely used like serial port.

References

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