Audio gain adjustment and access switching circuit for rail transit vehicle-mounted radio station

Abstract

The invention discloses an audio gain adjustment and access switching circuit for a rail transit vehicle-mounted radio station. Comprising an audio coding and decoding chip, a reset circuit, a first operational amplifier, a first audio transformer circuit, a second operational amplifier, a second audio transformer circuit, a single-chip microcomputer containing a control program, and a crystal oscillator circuit. The single-chip microcomputer connected with the crystal oscillator is in bidirectional connection with the audio coding and decoding chip connected with the reset circuit, the audio coding and decoding chip is respectively in bidirectional connection with the two operational amplifiers, and the two operational amplifiers are respectively connected with the two audio transformers. According to the scheme, the circuit design of an audio channel is greatly simplified, firstly, the types and the number of used components are greatly reduced, and the space of a circuit board and the cost of the circuit board are saved; and secondly, as one core element is selected and adopted, the complexity of a control process is reduced, some software BUG hidden dangers caused by the complexity of the control process are avoided, and the vehicle-mounted radio station is more stable and reliable in operation.

Description

Technical Field

[0001] The invention relates to a rail transit vehicle-mounted radio station, and in particular to an audio gain adjustment and path switching circuit for a rail transit vehicle-mounted radio station. Background Art

[0002] Metro rail transit is now an indispensable means of travel for people's daily travel. The vehicles running on the subway tracks are the carriers of passengers. The wireless dispatching communication system required for the vehicles to run on the tracks is a reliable guarantee for the safe operation of rail locomotives and vehicles. The on-board radio in the locomotive is an important part of the wireless communication dispatching system. The vehicle radio is an electronic communication device installed on locomotives and vehicles. It is an important equipment in the subway operation and dispatching system. It has multiple voice services including group calls, single calls, emergency calls, vehicle broadcasts, and emergency intercoms. Therefore, the audio circuit design of the vehicle radio is very important. Since the vehicle radio needs to realize multiple voice services, the design of the audio circuit needs to adopt multiple audio channels. In the original traditional design, one audio channel requires a digital potentiometer and an analog switch to adjust the gain and switch the channel of this audio channel. Generally, there are at least three audio channels, which require three digital potentiometers and three analog switches, as well as corresponding peripheral circuits. There are many devices and a large board space is required. In addition, each digital potentiometer needs to be individually controlled by software to adjust the gain value, which also increases the requirements for the processor in the vehicle radio circuit and adds more processing overhead. This also invisibly increases some software design risks and brings some instability. Summary of the invention

[0003] In view of the above problems in the prior art, in order to simplify the audio circuit design while meeting the multi-channel audio voice services of the vehicle radio, the present invention provides an audio gain adjustment and path switching circuit for rail transit vehicle radio.

[0004] The technical solution adopted by the present invention is: an audio gain adjustment and path switching circuit for a rail transit vehicle radio station includes four parts: an audio codec chip and a reset circuit, a first operational amplifier and a first audio transformer circuit, a second operational amplifier and a second audio transformer circuit, a single-chip microcomputer containing a control program, and a crystal oscillator circuit; wherein the single-chip microcomputer connected to the crystal oscillator is bidirectionally connected to the audio codec chip connected to the reset circuit, the audio codec chip is bidirectionally connected to the first operational amplifier and the second operational amplifier, respectively, and the first operational amplifier and the second operational amplifier are respectively connected to the first audio transformer circuit and the second audio transformer.

[0005] In the operation of rail transit vehicle radio, multiple audio channels including vehicle radio calls, vehicle radio broadcasts, and vehicle radio emergency intercoms need to be switched and the volume gain adjusted. Because the audio source of the vehicle radio comes from the audio part of the wireless channel machine inside the vehicle radio, the vehicle radio then outputs the audio of the wireless channel machine to the vehicle radio calls, vehicle radio broadcasts, and vehicle power supply. The original traditional circuit processing method is to place multiple digital potentiometers and analog switches for audio gain control and audio channel switching to meet the needs of multiple audio channels of the vehicle radio. The original traditional circuit method is very cumbersome and uses many components. This design does not use traditional digital potentiometers and analog switches, simplifies the circuit design scheme, and the circuit processing method is very simple.

[0006] The beneficial effects of the present invention are as follows: the audio part of the rail transit vehicle radio greatly simplifies the circuit design of the audio path through the design scheme. First, the types and quantities of components used are greatly reduced, saving the space and cost of the circuit board; second, because a core component is selected and adopted, the complexity of the control process is reduced, avoiding some software BUG risks caused by the cumbersome control process, making the operation of the vehicle radio more stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a block diagram of the connection principle of the present invention; Figure 2 It is the circuit schematic diagram of audio codec chip and reset chip; Figure 3 is a schematic diagram of a first operational amplifier and a first audio transformer circuit; Figure 4 is a schematic diagram of the second operational amplifier chip and the second audio transformer circuit; Figure 5 It is the schematic diagram of the microcontroller and crystal oscillator circuit; Figure 6 It is a flow chart of the microcontroller control program. DETAILED DESCRIPTION

[0008] The invention is further described below with reference to the accompanying drawings and embodiments.

[0009] Reference Figure 1A circuit for adjusting audio gain and switching channels of a rail transit vehicle radio station includes four parts: an audio codec chip and a reset circuit, a first operational amplifier and a first audio transformer circuit, a second operational amplifier and a second audio transformer circuit, a single-chip microcomputer containing a control program, and a crystal oscillator circuit; wherein the single-chip microcomputer connected to the crystal oscillator is bidirectionally connected to the audio codec chip connected to the reset circuit, the audio codec chip is bidirectionally connected to the first operational amplifier and the second operational amplifier, and the first operational amplifier and the second operational amplifier are respectively connected to the first audio transformer circuit and the second audio transformer.

[0010] Reference Figure 2 In the circuit of audio codec chip N2 and reset chip N5, the model of audio codec chip N2 is TLV320AIC3106IRGZ, and the model of reset chip N5 is SP809; pin 1 and pin 2 of audio codec chip N2 are connected to 3.3V power supply through resistors R6 and R7 respectively; pin 3, pin 4, pin 5, pin 6, pin 7 and pin 8 are connected to audio output interface CRX of vehicle radio channel machine through capacitors C31, C32, C34, C37, C39 and C40 respectively. DOUT+, car radio channel machine audio output interface CRXDOUT-, car emergency intercom audio input interface IPHINPUT+, car emergency intercom audio input interface IPHINPUT-, car radio audio input interface CRINPUT+, car radio audio input interface CRINPUT-, the 23rd, 22nd, 29th and 30th pins of the audio codec chip N2 are connected to the car radio channel machine audio input interface CRXDIN+, car radio channel machine audio input interface CRXDIN-, car radio speaker audio output interface CRSPOUT+, car radio speaker audio output interface CRSPOUT- through capacitors C20, C21, C26 and C27 respectively; the 33rd pin of the audio codec chip N2 is connected to resistor R16, one end of capacitor C28 and pin 2 of the system reset chip N5, pin 1 of the system reset chip N5 is grounded, pin 3 is grounded through capacitor C45, the other end of resistor R16 is connected to the 3.3V power supply, and the other end of capacitor C28 is grounded; audio codec chip N2 Pins 43, 45, and 46 are connected and grounded, and pins 15, 26, 20, 21, 0, and 42 are connected and grounded; pins 16, 17, 24, 25, and 44 are connected and connected to a 3.3V power supply, and pin 44 is connected to one end of capacitors C7, C8, and C9. Pin 36 of the audio codec chip N2 is connected to a 1.8V power supply, and pin 36 is connected to one end of capacitors C10 and C11, and the other ends of capacitors C7, C8, C9, C10, and C11 are connected and grounded.

[0011] Reference Figure 3In the circuit of the first operational amplifier chip N1 and the first audio transformer T1, the model of the first operational amplifier chip N1 is OPA172IDCKR, and the model of the first audio transformer T1 is VT-36003; one end of the capacitor C1, the resistor R2, and the inductor L1 is connected to a 5V power supply, the other end of the capacitor C1 is grounded, the other end of the resistor R2 is connected to the resistor R4, the resistor R8, and one end of the capacitor C14, the other end of the resistor R4 is connected to the positive pole of the primary coil of the first audio transformer T1, the negative pole of the primary coil is grounded, the positive pole of the secondary coil of the first audio transformer T1 is connected to the car broadcast audio interface CRB+, and the negative pole of the secondary coil is connected to the car broadcast audio interface CRB-; the other end of the resistor R8 is grounded, and the other end of the capacitor C14 is connected to the first operational amplifier chip Pin 4 of chip N1, resistor R1, and one end of capacitor C2, the other end of inductor L1 is connected to one end of capacitor C12, pin 5 of the first operational amplifier chip N1 and one end of resistor R9, the other end of capacitor C12 is connected to pin 2 of the first operational amplifier chip N1 and then grounded, the other ends of resistor R1 and capacitor C2 are connected to pin 3 of the first operational amplifier chip N1 and one end of resistor R3, pin 1 of the first operational amplifier chip N1 is connected to the other end of resistor R9 and one end of resistor R5 and resistor R10, the other ends of resistor R3 and resistor R5 are connected to the audio codec chip N2 through capacitor C13 and capacitor C15 respectively, and are connected to pins 18 and 19 of the audio codec chip N2 through capacitors C16 and capacitor C17; the other end of resistor R10 is grounded.

[0012] Reference Figure 4In the circuit of the second operational amplifier chip N3 and the second audio transformer T2, the model of the second operational amplifier chip N3 is OPA172IDCKR, and the model of the second audio transformer T2 is VT-36003; one end of the capacitor C18, the resistor R12, and the inductor L2 is connected to a 5V power supply, the other end of the capacitor C18 is grounded, the other end of the resistor R12 is connected to the resistor R14, the resistor R18, and one end of the capacitor C24, the other end of the resistor R14 is connected to the positive pole of the primary coil of the second audio transformer T2, the negative pole of the primary coil is grounded, the positive pole of the secondary coil of the second audio transformer T2 is connected to the vehicle emergency intercom audio output interface CRIPHOUT+, and the negative pole of the secondary coil is connected to the vehicle emergency intercom audio output interface CRIPHOUT-; the other end of the resistor R18 is grounded, and the other end of the capacitor C24 is connected Pin 4 of the second operational amplifier chip N3, resistor R11, and one end of capacitor C19, and the other end of inductor L2 are connected to one end of capacitor C22, pin 5 of the second operational amplifier chip N3, and one end of resistor R17. The other end of capacitor C22 is connected to pin 2 of the second operational amplifier chip N3 and then grounded. The other ends of resistor R11 and capacitor C19 are connected to pin 3 of the second operational amplifier chip N3 and one end of resistor R13. Pin 1 of the second operational amplifier chip N3 is connected to the other end of resistor R17 and one end of resistor R15 and resistor R19. The other ends of resistor R13 and resistor R15 are connected to the audio codec chip N2 through capacitor C23 and capacitor C25 respectively, and are connected to pins 31 and 32 of the audio codec chip N2 through capacitors C29 and capacitor C30; the other end of resistor R19 is grounded.

[0013] Reference Figure 5 In the single-chip microcomputer N6 and crystal oscillator circuit, the model of single-chip microcomputer N6 is STM32F407VET6. Pins 8 and 9 of single-chip microcomputer N6 are connected to the two ends of crystal oscillator G1 respectively, and are grounded through capacitors C46 and C47 respectively; pins 11, 19, 28, 50, 75, 100, and 22 of single-chip microcomputer N6 are connected to a 3.3V power supply, pins 10, 27, 74, and 99 are connected to ground, pin 20 is grounded, pin 21 is grounded through capacitor C48, and pins 92 and 93 are connected to pins 1 and 2 of the audio codec chip N2 respectively.

[0014] Reference Figure 6 The MCU control program performs the following operations: after power-on, the audio codec chip is initialized, and the MCU sends the audio channel and gain instructions to the audio codec chip through bus communication. According to the contents of the audio channel and gain instructions, it is determined which audio channel to switch. If it is determined which audio channel it is, the audio channel is switched and the corresponding gain adjustment is performed. If it is not determined which audio channel it is, it returns to continue waiting for the audio channel and gain instructions before making another judgment.

[0015] The core of this design is the audio codec chip N2, model TLV320AIC3106IRGZ, which is used to set audio gain and switch audio paths. The existing design mostly uses multiple digital potentiometers and multi-channel analog audio switches, which are cumbersome in circuit design and complex in control process. We choose to use an audio codec chip for unified switching paths and gain adjustment.

[0016] When the differential audio signal of "car radio channel audio output interface CRXDOUT+, car radio channel audio output interface CRXDOUT-" CRXDOUT is input to the two pins 3 and 4 of the audio codec chip N2, the audio path control of the audio codec chip N2 can be switched to the 18, 19 pins and 29, 30 pins and 31, 32 pins of the audio codec chip N2 through software control, and output to the three audio paths of car broadcasting, emergency intercom, and car radio speaker output according to needs, and can also control the gain of each signal, which can completely replace the traditional use of 3-way digital potentiometers and 3-way analog switches for gain setting and path switching, avoiding the cumbersome design of multiple devices in the circuit, and the design is simple and the control method is not complicated, and the effect is very good.

Claims

1. A circuit for adjusting audio gain and switching channels of a rail transit vehicle radio, characterized in that: The circuit includes four parts: an audio codec chip and a reset circuit, a first operational amplifier and a first audio transformer circuit, a second operational amplifier and a second audio transformer circuit, a single-chip microcomputer containing a control program, and a crystal oscillator circuit; wherein the single-chip microcomputer connected to the crystal oscillator is bidirectionally connected to the audio codec chip connected to the reset circuit, the audio codec chip is bidirectionally connected to the first operational amplifier and the second operational amplifier, respectively, and the first operational amplifier and the second operational amplifier are respectively connected to the first audio transformer circuit and the second audio transformer.

2. The audio gain adjustment and path switching circuit for rail transit vehicle radio according to claim 1 is characterized in that: In the circuit of the audio codec chip N2 and the reset chip N5, the model of the audio codec chip N2 is TLV320AIC3106IRGZ, and the model of the reset chip N5 is SP809; the pins 1 and 2 of the audio codec chip N2 are connected to the 3.3V power supply through resistors R6 and R7 respectively; the pins 3, 4, 5, 6, 7 and 8 are connected to the car radio channel machine audio output interface CRXDOUT+, the car radio channel machine audio output interface CRXDOUT-, the car emergency intercom audio input interface IPHINPUT+, the car emergency intercom audio input interface IPHINPUT-, the car radio audio input interface CRINPUT+, the car radio audio input interface CRINPUT- through capacitors C31, C32, C34, C37, C39 and C40 respectively, and the audio Pins 23, 22, 29 and 30 of the audio codec chip N2 are connected to the audio input interface CRXDIN+ of the vehicle radio channel machine, the audio input interface CRXDIN- of the vehicle radio channel machine, the audio output interface CRSPOUT+ of the vehicle radio speaker, and the audio output interface CRSPOUT- of the vehicle radio speaker through capacitors C20, C21, C26 and C27 respectively; Pin 33 of the audio codec chip N2 is connected to resistor R16, one end of capacitor C28 and pin 2 of the system reset chip N5, pin 1 of the system reset chip N5 is grounded, pin 3 is grounded through capacitor C45, the other end of resistor R16 is connected to a 3.3V power supply, and the other end of capacitor C28 is grounded; Pins 43, 45 and 46 of the audio codec chip N2 are connected and then grounded, and pins 15, 26, 20, 21, 0 and 42 are connected and then grounded; Pins 16, 17, 24, 25, and 44 are connected to a 3.3V power supply, and pin 44 is connected to one end of capacitors C7, C8, and C9. Pin 36 of the audio codec chip N2 is connected to a 1.8V power supply, and pin 36 is connected to one end of capacitors C10 and C11. The other ends of capacitors C7, C8, C9, C10, and C11 are connected and grounded.

3. The audio gain adjustment and path switching circuit for rail transit vehicle radio according to claim 2 is characterized in that: In the circuit of the first operational amplifier chip N1 and the first audio transformer T1, the model of the first operational amplifier chip N1 is OPA172IDCKR, and the model of the first audio transformer T1 is VT-36003; one end of the capacitor C1, the resistor R2, and the inductor L1 are connected to a 5V power supply, the other end of the capacitor C1 is grounded, the other end of the resistor R2 is connected to one end of the resistor R4, the resistor R8, and the capacitor C14, the other end of the resistor R4 is connected to the positive pole of the primary coil of the first audio transformer T1, the negative pole of the primary coil is grounded, the positive pole of the secondary coil of the first audio transformer T1 is connected to the car broadcast audio interface CRB+, and the negative pole of the secondary coil is connected to the car broadcast audio interface CRB-; the other end of the resistor R8 is grounded, and the other end of the capacitor C14 is connected to the first operational amplifier Pin 4 of chip N1, resistor R1, and one end of capacitor C2, and the other end of inductor L1 are connected to one end of capacitor C12, pin 5 of the first operational amplifier chip N1, and one end of resistor R9. The other end of capacitor C12 is connected to pin 2 of the first operational amplifier chip N1 and then grounded. The other ends of resistor R1 and capacitor C2 are connected to pin 3 of the first operational amplifier chip N1 and one end of resistor R3. Pin 1 of the first operational amplifier chip N1 is connected to the other end of resistor R9 and one end of resistor R5 and resistor R10. The other ends of resistor R3 and resistor R5 are connected to the audio codec chip N2 through capacitor C13 and capacitor C15 respectively, and are connected to pins 18 and 19 of the audio codec chip N2 through capacitors C16 and capacitor C17; the other end of resistor R10 is grounded.

4. The audio gain adjustment and path switching circuit for rail transit vehicle radio according to claim 3 is characterized in that: In the circuit of the second operational amplifier chip N3 and the second audio transformer T2, the model of the second operational amplifier chip N3 is OPA172IDCKR, and the model of the second audio transformer T2 is VT-36003; one end of the capacitor C18, the resistor R12, and the inductor L2 is connected to a 5V power supply, the other end of the capacitor C18 is grounded, the other end of the resistor R12 is connected to the resistor R14, the resistor R18, and one end of the capacitor C24, the other end of the resistor R14 is connected to the positive pole of the primary coil of the second audio transformer T2, the negative pole of the primary coil is grounded, the positive pole of the secondary coil of the second audio transformer T2 is connected to the vehicle emergency intercom audio output interface CRIPHOUT+, and the negative pole of the secondary coil is connected to the vehicle emergency intercom audio output interface CRIPHOUT-; the other end of the resistor R18 is grounded, and the other end of the capacitor C24 is connected Connect to pin 4 of the second operational amplifier chip N3, resistor R11, and one end of capacitor C19, the other end of inductor L2 is connected to one end of capacitor C22, pin 5 of the second operational amplifier chip N3 and one end of resistor R17, the other end of capacitor C22 is connected to pin 2 of the second operational amplifier chip N3 and then grounded, the other ends of resistor R11 and capacitor C19 are connected to pin 3 of the second operational amplifier chip N3 and one end of resistor R13, pin 1 of the second operational amplifier chip N3 is connected to the other end of resistor R17 and one end of resistor R15 and resistor R19, the other ends of resistor R13 and resistor R15 are connected to the audio codec chip N2 through capacitor C23 and capacitor C25 respectively, and are connected to pins 31 and 32 of the audio codec chip N2 through capacitors C29 and capacitor C30; the other end of resistor R19 is grounded.

5. The audio gain adjustment and path switching circuit for rail transit vehicle radio according to claim 4 is characterized in that: In the single-chip microcomputer N6 and crystal oscillator circuit, the model of the single-chip microcomputer N6 is STM32F407VET6, and the 8th and 9th pins of the single-chip microcomputer N6 are respectively connected to the two ends of the crystal oscillator G1, and are grounded through capacitors C46 and C47 respectively; the 11th, 19th, 28th, 50th, 75th, 100th and 22nd pins of the single-chip microcomputer N6 are connected to a 3.3V power supply, the 10th, 27th, 74th and 99th pins are connected to ground, the 20th pin is grounded, the 21st pin is grounded through capacitor C48, and the 92nd and 93rd pins are respectively connected to the 1st and 2nd pins of the audio codec chip N2.

6. The audio gain adjustment and path switching circuit for rail transit vehicle radio according to claim 1 is characterized in that: The single-chip microcomputer control program performs the following operations: after power-on, the audio codec chip is initialized, and the single-chip microcomputer sends audio channel and gain instructions to the audio codec chip through bus communication. It determines which audio channel to switch based on the content of the audio channel and gain instructions. If it is determined which audio channel it is, the audio channel is switched and the corresponding gain adjustment is performed. If it is not determined which audio channel it is, it returns to continue waiting for the audio channel and gain instructions before making another judgment.

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