Relying on high-performance IP phone voice terminal hardware design
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Abstract : This paper designs a high-performance IP telephony voice terminal system hardware platform for IP telephony communication in Ethernet based on Motorola and TI's TMS320C5402 digital signal processor. The problem that the conventional communication processing capability using only the digital signal processor is not high is solved.
1 Overview IP telephony is a technology that uses the Internet or other IP networks (such as intranet, frame relay, or ATM) as a transmission carrier to implement voice communication between ordinary telephones and ordinary telephones, PCs and PCs, PCs, and ordinary telephones. Therefore, IP phones are also called VoIP (Internet Telephony) or VoIP (Voice over IP). IP telephony is different from traditional telephony. It uses packet switching technology. Packets are transmitted on the network instead of voice signals. Therefore, the voice signals are quantized, encoded, compressed, and packed (grouped) to be changed. For the data stream, it is transmitted to the other party and then inversely transformed, and finally restored to a voice signal. Since IP telephony adopts packet switching and statistical multiplexing technology, the integrated transmission of voice and data is realized, and the operating cost of the entire network is greatly reduced, so that the communication cost to which the user bears is greatly reduced. Using advanced digital signal processing technology, the original 64 kb voice signal can be compressed into a data stream of 8 kb or lower, which can transmit more information on the same line than analog technology. In the past, IP telephone terminals used DSP as the main processor. This system is still ok for voice signal processing, but the communication capability is weak. Because of this, this paper designs an IP telephony voice terminal system based on Motorola and TI's TMS320C5402 digital signal processor, which aims to realize IP telephony communication in Ethernet.
2 system overall structure
The MPC860 microprocessor is a member of the Power QUICC family from Motorola and is a versatile communications processor chip. It uses a dual processor architecture of embedded power PC core and communication processor module (CPM). The embedded Power PC core is responsible for general-purpose work. The CPM shares the peripheral tasks of the embedded Power PC core, mainly for communication services. This dual processor architecture consumes less power than traditional architecture processors. TMS320C5402 is a low-power and high-performance dedicated fixed-point DSP chip produced by Texas Instruments. It has 16kb RAM and 4kb ROM. The operation speed is much faster than that of ordinary processors. It is very suitable for digital signal processing with high real-time requirements. .
In this system, communication requirements and digital signal processing requirements are high. TI's DSP is widely used in digital signal processing with its powerful digital signal function, but its communication capability is weak. MPC860's powerful function lies in its communication processing capability, which just makes up for the shortcomings of TMS320C5402. Based on the respective strengths of MPC860 and TMS320C5402, after analysis, the following IP phone terminal system hardware solutions are given:
The whole system is mainly composed of a main control module, a control display module and a voice sampling and playing module. The main control module is composed of MPC860, which realizes the core control of the whole system; the voice processing module is composed of TMS320C5402 digital signal processor, which is the voice signal processing core of the whole system; the network control module is composed of LXT905, which completes the communication between the whole system and Ethernet. The voice sampling and playback module is mainly composed of TLC320AD545, which is responsible for sampling and converting the system voice signal and finally playing the voice. Among them, MPC860 and TMS320C5402 are the core parts of the whole system, which complete the control of the whole system and the processing of voice signals.
3 Design of main control module and voice processing module
The MPC860 of the main control module is a processor designed by Motorola for communication applications. In this system, the communication functions such as network protocol, signaling interaction and call processing of the system are completed, which is the call control core of the whole system. The TMS320C5402 of the voice processing module is designed by the IT company for digital signal processing. In this system, the functions of encoding, decoding, and compressing voice signals are completed, which is the core unit of voice signal processing of the whole system.
In the system, the MPC860 of the main control module and the TMS320C5402 of the voice processing module adopt a master-slave connection. The MPC860 acts as the master and the TMS320C5402 acts as the slave. The two communicate through the HIP interface, and the connection is simple. This will play the communication control of the MPC860 and take advantage of the digital signal processing of the TMS320C5402.
In the process of voice processing of the system, a certain storage space is required. The 16K on-chip storage space of the TMS320C5402 digital signal processor cannot meet the requirements of the voice processing process, so the memory expansion is required. The TMS320C5402 has a memory expansion, and the MPC860's memory controller comes with eight memory slots. Therefore, in this system, the expansion of the memory can be performed in the TMS320C5402 or in the MPC860. In this system, in order to keep the MPC860 better control and compact function of the whole system, it is expanded on the MPC860 here. After analysis and comparison, it was decided to use one 4MB Flash E2PROM and two 16MB SDRAM. Among them, Flash E2PROM adopts Intel's 28F320B3, which occupies BANKO, corresponding to /CS0 chip select signal, memory management mechanism selects GPCM (universal chip select mechanism), data bus width is 32 bits, SDRAM adopts K45281632B of SAMSUNG company. Occupying BANKI, corresponding to the /CS1 chip select signal, the memory management mechanism selects UPMA (user programmable mechanism), two SDRAMs are used in parallel, and the data bus width is 32-bit. as shown in picture 2.
4 network control module design
The network control module is based on the LXT905 universal 10BASE-T transceiver manufactured by Intel Corporation, and then provides a direct connection to the nearby unit interface AUI or 10BASE-T twisted pair through the 232467SM transformer. Complete system and Ethernet communication, including: Manchester codec, receive suppression and transmit pulse shaping, link integrity test, 10BASE-T polarity flip detection and correction.
There are four serial communication controllers SCC in the MPC860, which can be configured separately to implement different protocols, such as bridging, routing, gateway functions, etc., providing interfaces to WAN, LAN and private networks. Set the general SCC mode register GSMR[MODE]=ob1100 to select Ethernet. The SCC will perform the Ethernet/IEEE 802.3 media access control MAC for all CSMA/CD and provide the interface for the channel. Since the IP telephone terminal system we designed is mainly used in Ethernet to communicate, the SCC is defined here as the Ethernet mode.
Figure 3 shows the signal connection method from MPC860 to Ethernet. A serial interface adapter SIA (RJ-45) and transceiver are required to interface to the media outside of the MPC860 and Ethernet controllers.
The MPC860 core configures the SCC to work for the Ethernet controller. In addition to setting the general SCC mode register, it is also necessary to set other fields of the GSMR to specific values. If the data synchronization register DSR is used to specify the synchronization pattern of the frame, it is necessary to set DSR[SYN1]=ox55, DSR[SYN2]=oxDE in Ethernet mode. The transceiver error message will be recorded in the SCC Ethernet Receive Buffer Descriptor RxBD and the SCC Ethernet Transmit Buffer Register TxBD.
5 other module design
At the heart of the voice sampling and playback module is the TLC320AD545, a high-end audio codec from TI. The voice sampling module consists of a codec TLC320AD545, an analog circuit and a serial port. It also includes a microphone, an amplifier circuit, and a speaker driver circuit. as the picture shows:
The main functional indicators of TLC320AD545: the highest sampling rate of 11.025Hz, 16bit sampling, 80db dynamic range, 8 ohm AT41 differential speaker drive. The A/D channel and the microphone complete the digitization of the voice, and the D/A is connected to the speaker to convert the received digitized voice into an analog voice. The serial port is connected to the serial port of the TMS320C5402 to complete data transmission. The control display module mainly implements the system LCD display.
6 Conclusion
Based on Motorola's MPC860 and TI's TMS320C5402 digital signal processor, this paper designs a high-performance IP telephony voice terminal system for IP telephony communication in Ethernet. It solves the problem that the communication processing capability of the conventional digital signal processor is not high, and has certain significance for the development of today's IP telephone.
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Low Noice Speaker Cable,Speaker Cable,Speaker Wire
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