Small voice system composed of GMS97C2051 and ISD2560

    Abstract: This article introduces the computer voice system composed of the single-chip computer GMS97C2051 and the voice chip ISD2560, and gives the practical circuit, recording and playback program block diagram and source program. The system hardware circuit is simple, easy to debug, cost-effective and practical. It can be used as the voice board of the computer voice service system and has certain practical and reference value.

    Keywords: GMS97C2051 microcontroller ISD2560 voice chip segmented recording combination playback

    At present, the computer voice service industry is becoming more and more widespread, such as computer voice clocks, voice-based digital multimeters, mobile phone bill inquiry systems, queuing machines, bus stop announcers, etc. The author designed a microcomputer voice board using the single-chip microcomputer GMS97C2051 and ISD2560, which realizes segmented recording and combined playback of speech. Through software modification, the entire segment recording and loop playback can also be realized. The system completes the voice recording and playback function and can be used as a subsystem of the voice service system without using special ISD voice development equipment.

1 System introduction and interface circuit

　　GMS97C2051 is a powerful microcontroller produced by LG Semiconductor, which provides a highly flexible and effective solution for many embedded control application systems. GMS97C2051 comes with 2K bytes of programmable EEPROM, 128 bytes of RAM, 15 I/O lines, two 16-bit timer/counters, a fully bidirectional serial port, a precision comparator, etc. It is instruction set and pin compatible with the industry standard MCS-51. The pin arrangement is shown in Figure 1(a).

　　Port P1 is a bidirectional I/O port. Ports P1.2~P1.7 provide internal pull-up resistors, and P1.0 and P1.1 require external pull-ups. P1.0 and P1.1 are also the positive input terminal (AIN0) and negative input terminal (AIN1) of the on-chip precision comparator. Port P3 is 7 bidirectional ports with internal pull-up resistors (except P3.6, which is the output pin of the on-chip comparator and cannot be used as an ordinary I/O port). For specific performance of GMS97C2051, please refer to reference [1].

　　ISD2560 is one of the ISD series single-chip voice recording and playback integrated circuits. It is a permanent memory voice recording and playback circuit. The recording time is 60 s and can be repeated up to 100,000 times. It uses direct level storage technology, eliminating the need for A/D and D/A converters. ISD2560 is highly integrated and includes preamplifier, internal clock, timer, sampling clock, filter, automatic gain control, logic control, analog transceiver, decoder and 480 Kbytes of EEPROM, etc. The internal EEPROM storage unit is evenly divided into 600 rows and has 600 address units. Each address unit points to one of the rows. The address resolution of each address unit is 100 ms. ISD2560 control level is compatible with TTL level, the interface is simple and easy to use. The pin arrangement is shown in Figure 1(b).

　　◇ A0~A9 are address lines, with a total of 1024 combination states. The first 600 states are used for addressing internal memory, and the last 256 states are used as operating modes. For specific usage, see reference [2]. This system adopts the method of direct operation on the address.

　　◇ Microprocessor interface: P/R recording and playback control terminal. When this terminal is at high level, it is in the playback state, and when it is at low level, it is in the recording state. This terminal is used for start and stop control during recording and playback, usually with P/R The terminal is used in conjunction with the terminal; the terminal is the output terminal of the end signal of each segment of information. It is a negative signal with a time of 12.5 ms. The rising edge marks the end of the information.

　　◇ MIC IN is the microphone preamplifier input terminal; MIC REF is the microphone compensation terminal, and the circuit connected to the microphone is shown in Figure 2; AGC automatic gain control terminal; ANA IN and ANA OUT are the input terminals and output terminals of analog signals. Connect a coupling capacitor between them, usually with a value of 0.22~1μF.

　　The interface circuit and peripheral circuit between ISD2560 and microcontroller GMS97C2051 are shown in Figure 2. The P1 port, P3.4 and P3.5 of the microcontroller are connected to the address line of ISD2560 to set the starting address of the voice segment. P3.0~P3.3 are used to control the recording and playback status. P3.7 expands a recording key for use during recording. The specific performance and usage of ISD2560 can be found in reference [2].

2 System working principle and program design

2.1 ISD2560 internal address unit addressing

　　Although ISD2560 provides an address input line, the address of its internal information segment cannot be read. Typically an operating mode is used which does not require knowledge of the address, but this does not satisfy the different practical needs. Generally, direct operation on the address is used, but reading out the internal information address of ISD2560 requires special ISD development equipment, which is relatively expensive. This system is controlled by a single-chip microcomputer. It does not need to read out the information address, but directly sets the starting address of the information segment. There are many ways to implement it. One way is: since the address resolution of ISD2560 is 100 ms, the internal timer of the microcontroller can be used to time for 100 ms, and then a counter is used to count the number of times the microcontroller has been timed. The count value of the counter is The address unit occupied by the speech segment. This method can make full use of the EEPROM inside the ISD2560 and can be used when there are many fields. Please refer to reference [4] for the specific use of this method. If there are fewer voice fields, the following method can be used: directly allocate address units according to the content of each field. Generally speaking, 3 words are spoken every 1 s, and 180 words can be spoken in 60 s. Based on the address resolution of ISD2560 being 100 ms, the number of address units required for the speech segment can be calculated. This system adopts this method.

2.2 Control of ISD2560 by GMS97C2051 microcontroller during recording and playback

　　When recording, press the recording button, the microcontroller sets the starting address of the voice segment through the mouth line, and then sets the PD terminal, P/R terminal and terminal to low level to start recording; at the end, release the button, and the microcontroller returns the terminal. to high level, the recording of a piece of voice is completed. The same method can be used to enroll the second paragraph, the third paragraph, and so on. It is worth noting that the recording time cannot exceed the preset time of each voice segment.

　　When playing, find the starting address of the corresponding voice segment based on the voice content to be played, and send it out through the mouth line. Then set the P/R terminal to high level, set the PD terminal to low level, and let the terminal generate a negative pulse to start playback. At this time, the microcontroller only needs to wait for the information end signal of ISD2560, that is, the generation of. The signal is a negative pulse. On the rising edge of the negative pulse, the voice segment ends. Therefore, the microcontroller must detect the rising edge to play the second segment. Otherwise, the voice played will not be continuous and a popping sound will be produced. This must be paid attention to when compiling software. The sound recording and playback program block diagram is shown in Figure 3 and Figure 4.

2.3 System interface source program

　　The following is a recording program for recording 5 pieces of voice information and a source program for combined playback of these 5 pieces of voice information. During playback, the playback can be combined according to the actual situation. This program can be expanded when necessary.