A design scheme for a multifunctional recording and amplification system

0 Introduction

Safety is the first priority for power enterprises. In power work, including dispatch pre-orders, operating instructions, operating steps, operating reports, situation reports, etc., telephone recording is required. Recording can better urge relevant personnel to strictly abide by safety procedures and labor discipline, which greatly promotes power safety production. At present, Fujian and Zhejiang regions have successively carried out quasi-military work on power systems, which has played a good role in promoting the regularity and safety of power production. At the same time, recording requirements are put forward for operating steps, work content, safety measures, division of labor, etc. in maintenance work. However, traditional recorders, recorders, etc. are not convenient for use in work due to their functions, capacity, convenience, etc.

1 Recording and amplification system structure

Multifunctional recording and amplification system, which mainly includes ARM data processing module, recording system, and amplification system. The system is applicable, portable, and easy to operate. Among them, the recording system is used to record the work content, dangerous points, safety measures and division of labor arrangements before work in power maintenance work; the amplification system assists the person in charge of the work to amplify the above work, especially in large-scale maintenance or occasions with a large number of people, etc., which promotes power safety production, and has an audio playback function, which can play MP3 music and recorded language. It also supports voice-controlled recording function: it automatically pauses recording when the external sound is too small, and automatically continues recording when there is sound. The system structure block diagram is shown in Figure 1. 2 Design of the hardware platform of the new recording and playback system The CPU of the multifunctional recording and amplification system adopts a 32-bit ARM processor-AT91SAM9263, the recording module adopts a voice chip with excellent performance, the ISD4004 voice chip produced by the American ISD company, and the amplification module is based on the widely used TEA2025 amplifier chip. 2.1 ARM module The AT91SAM9263 microcontroller produced by the American ATMEL company. The controller is based on the industrial-grade system-on-chip (SoC) chip of ARM9263EJ-S; it has rich on-chip resources and standard interfaces, as well as low power consumption, low cost, high performance, support for multiple major embedded operating systems, and has extremely strong audio processing capabilities. The specific wiring diagram of the minimum system of the AT91SAM9263 chip is shown in Figure 2. This system uses active crystal oscillator X1 (18.432MHz) and passive crystal oscillator X2 (32.768kHz) as the main oscillator and slow clock oscillator of the system. The system main clock and slow clock reference generated by the oscillator pass through two PLLs (Phase Locked Loops) inside the microprocessor to generate various CPU clocks, peripheral clocks and USB device working clocks required by the system. 2.2 Recording module The recording module is a recording system based on ISD4004. The ISD4004 chip can be directly stored without A/D conversion and compression, and there is no A/D conversion error. It has the characteristics of repeated recording and playback, long storage time, no need to expand the memory when using, and simple peripheral circuits. The pins include power supply, clock, voice signal analog input/output terminal, and MCU interface (SPI interface). The chip adopts multi-level direct analog storage technology. Each sample value is directly stored in the on-chip flash memory, so it can reproduce the voice very realistically and naturally. The specific wiring of the recording module circuit is shown in Figure 3. [page] The module is controlled by voice control and panel keys, including starting, pausing and stopping recording. At the same time, during the recording process, if the sound is less than the set value, the recording will be automatically paused, and when the sound rises again, the recording will automatically continue. 2.3 Sound reinforcement system The sound reinforcement module adopts TEA2025 power amplifier chip and audio, with an output power of up to 4.7W, and the sound output is clear and loud. TEA2025 is a dual-channel power amplifier integrated circuit produced in Europe. The circuit has the characteristics of high channel separation, low impact noise when the power is turned on, few external components, and the maximum voltage gain can be adjusted by external resistors. It is used for power amplification in pocket or portable stereo sound systems. The specific wiring of the sound reinforcement module circuit is shown in Figure 4. The MIC signal goes to the recording module for recording, and first enters the transistor Q1 common emitter amplification. The quiescent current of the transistor Q1 is about 1mA, and the collector quiescent voltage is about 3V. After the voice signal is amplified by Q1, it is sent to the power amplifier TEA2025 through C8 for power amplification. The amplification module is connected to the microphone signal and is controlled by the recording system. It can be used to play and audition the recorded files. 2.4 The SD storage module uses the SD/MMC card controller integrated in the microprocessor. The SD/MMC card interface is designed in the system, so that the system can use the SD/MMC card to store the measurement data process, which effectively enhances the data storage function of the system. This card is controlled by a 6-wire SD card interface. The interface circuit of the SD/MMC card is shown in Figure 5.

3 Software Design

At present, there are many operating systems to choose from. Here we use µC/OS-II. µC/OS-II has the characteristics of high execution efficiency, small footprint, excellent real-time performance and strong scalability. The minimum kernel can be compiled to 2KB.

3.1 µC/OS-II initialization startup design

Before using all services of µC/OS-I, the function OSInit() must be used to implement initialization and initialize all global variables and data structures. At the same time, the OSInit() function will create an idle task OSTaskIdle, assign the lowest priority to the task and put it in the ready state. If the user application also wants to use the statistical task, then create the statistical task OSTaskstat() and let it enter the ready state. The priority of this task is set to OS_LOWESTPRIG_1. The system initialization process is shown in Figure 6. [page] 3.2 µC/OS-II porting design The file system structure of mC/OS-II includes the core code part, the setting code part, and the porting code part related to the processor. The top software application layer is the code on mC/OS-II. The core code part includes 7 source code files and 1 header file. The functions are kernel management, event management, message queue management, storage management, message management, semaphore processing, task scheduling and timing management. The setting code part includes 2 header files, which are used to configure the number of event control blocks and whether to include message management related codes. The porting code part related to the processor is the part that needs to be changed during the porting process, including 1 header file OS_CPU.H, 1 assembly file OS_CPU_A.S and 1 C code file. In fact, the work that needs to be completed to port mC/OS-II to the AT91RM9263 processor is mainly the following three files related to the architecture: OS_CPU.H, OS_CPU.C and OS_CPU_A.S. 3.3 Main program flow The main program flow chart of the control program is shown in Figure 7, which includes six subroutines such as time correction, recording, playback, playback time setting, and playback selection. 4 Conclusion This paper proposes a design scheme for a multifunctional recording and amplification system. This scheme fully utilizes the rich characteristics of ARM interfaces. After transplanting the efficient and stable µC/OS-II operating system, it has multiple functions such as amplification, recording, and playback, which meets the needs of safe production in power systems. Experiments have proved that this scheme has strong practicality.