PT2258-based multi-channel audio AV5.1 the control system
With the increase in income, consumers have long been easy to get good, cheap source of video and audio signals, such as RADIO, TV, CD, VCD, DVD, etc., in particular, VCD, DVD popularity, it is generally the AV amplifier move home, and gradually realized the sound of home theater. However, the above-mentioned audio signal sources have their own independent audio, control channel is independent, the use of red tape when it is not allowed to share the source of many AV amplifier audio sound quality, reduce the use of the fun.
In this context, the current source of family control of large number of discrete audio signals, we developed the PT2258-based audio control system AV5.1 to provide a high cost-effective, easy-to-use audio control infrared remote control platform will be the source of a variety of audio signal input to the AV amplifier, unified control. The control system has been successfully applied to a sound Enterprise in Shenzhen have been working well.
1 hardware circuit
The design for Microchip's PICl6C56 master IC, system hardware circuit diagram shown in Figure 1. Through analog switches select the source of audio signal input to the PT2258 chip-channel volume control by control IC for receiving, analyzing the keyboard or infrared remote control module of the data, control the volume of movements to achieve PT2258, stress change, mute switch and other functions Finally, the output of the AV amplifier to follow-up.
1.1-channel control PT2258
Prudential Cape PT2258 is a CMOS process launched by the channel volume control IC. Its wide operating voltage range (5 ~ 9 V), 6-channel design (O ~ a 79 dB), extremely low noise (S / N> l00 dB), high-resolution (> 100 dB), very few of the peripheral circuits as well as with the processor to facilitate I2C control bus connected to the car audio, computer multimedia, AV audio-visual areas such as around a wide range of applications, is a multi-channel AV excellent sound system volume control device. PT2258 external circuit connected as shown in Figure 2.
PT2258 former class INl ~ IN6 then 6-channel audio sources (through pre-selection of analog switches), 0UTl ~ 0UT6 after the output level to the left, middle, right, left, right, and after six active overweight bass speaker ; the first pin 6,7 for I2C pin through a pull-up resistor connected MCU's I / O port. mcu in accordance with the I2C transmission PT2258 timing to send and receive data, can be carried out on the overall volume control, can also be an independent regulator to a single channel (for example, BASS), the minimum number of 1 dB per band tuning effect of a similar linear processing, also programmable to achieve greater than 1 dB per band adjustment. This user-friendly software designed for the treble, bass quickly switch to the moderate volume of great significance, and can quickly achieve the mute (MUTE). In addition, the chip built-in 6-channel converter and low-frequency low-pass filter, deputy to ensure that the input signal pre-distortion to a very low level after the output to.
1.2 microcontroller PICl6C56
PICl6C56 as Microchip company launched the first of a series PICl6C5X, is a high-performance RISC architecture microcontroller 12. It inherited the PICl6C5X series of single-chip high-speed, low-cost, low power, low-voltage work, anti-good, easy to use many of the benefits of development, in household appliances, instrumentation, industrial areas and popular performers. PICl6C56 with 12 high-drive capability of the I / 0 port, designed to meet the needs of the system, while a slight margin for future system expansion.
1.3 analog audio source switch
The design involved four audio sources, VCD / DVD 6-channel, and the remaining 2 channels to choose 3 as the audio source CD4053 analog switch MCU can control I / O port to save 3. CD4053 is a 32-channel analog switch control, there are three independent control inputs and can end with a low-resistance and very low cut-off leakage current, it is more desirable to the multi-channel digitally controlled analog switches, circuit in Figure 3 show. 6 the input signal before (FR_I, FL_I, RR_I, RL_I, C_I, BASS_I) for VCD / DVD channel, and the rest for the CD, TV, RADIO, the two channels, with 3 MCU I / O combination of control sources the choice of input signals, such as listed in Table 1.
Infrared Remote Control 1.4
This module, including encoding, decoding in two parts. Encoding circuit system using a dedicated infrared remote control transmitter IC BL6121. It uses CMOS technology production, up to 64 external buttons, wide operating voltage range (2.2 ~ 5.5 V), for such a portable remote control device is especially suitable power supply, which constitute the circuit chip shown in Figure 4 shown. BL6121 external 455 kHz clock crystal, when the 36 ms time to reach the keys, the launch of an infrared data format code by a guide, 16-bit address code, 8-bit data code, anti-8-bit data code consists of data output waveform, see references. Receive infrared signals to the process, in fact, the infrared light signals into TTL signals in the process of integration is now widely used higher up to deal with the integration of receiving, and then will be converted into a TTL signal input of the MCU's I / O decode mouth. PIC16C56 without interruption, in the software design methodology to use to decode the query.
1.5 extension of the keyboard
Figure 5 below, using interactive keyboard design, RB0 ~ RB4 through pull-up resistor connected to the keyboard. Each I / O port for input line is also out for the output, input and output interactive use, constitute a 5 line 5. Each line in the ranks of independent (non-repetition) of the point of intersection, the set of a button, that is, any I / 0 lines are among the key after another. When a low-level output of a line, the other I / O lines are read into the key information, software design cycle of inquiry to determine the method keys. This design in the key the same number of cases, the occupation of I / O line low, save resources.
2 Software design
Microchip offers the MPLAB integrated development environment, in accordance with the procedure shown in Figure 6 the realization of software programming flow. VOLUME power system will be the initial volume for the moderate (a 10 dB), then determine whether there is local availability of keys, as well as infrared signal pin, according to keys and the case of infrared decoder function to the subroutine. Modular software design, readability, and maintenance, upgrades easy.
PT2258-based audio control system of AV5.1 not only a large number of discrete audio source centralized management, but also take full advantage of the acoustics of the AV amplifier. The system is easy to use, stable, intelligent home equipment in the case of updates, intelligent entertainment for the family provides a feasible means of control.
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