Automatic transmitting and receiving switching circuit

Abstract

The utility model discloses an automatic transmitting and receiving switching circuit, and relates to the technical field of transmitting and receiving circuits, and a serial communication chip in the circuit comprises a signal receiving pin, a signal transmitting pin and a mode switching pin; the mode switching pin is connected with the power supply voltage end through the second resistor; the mode switching pin is also grounded through a switching tube; the control end of the switching tube is grounded through the first capacitor; the control end of the switching tube is also connected to a signal sending pin through a first resistor; and the control end of the switch tube is also connected to a signal sending pin through a diode. According to the circuit, the threshold level arrival time of the mode switching pin can be controlled by adjusting the resistance-capacitance parameters on the circuit, so that the enable signal shaping of the mode switching pin is realized, the on-line data duty ratio of the serial communication chip can be controlled to a certain extent, and the signal transmission quality is improved.

Description

Technical Field

[0001] The present application relates to the technical field of transceiver circuits, and in particular to an automatic transceiver switching circuit. Background Art

[0002] Figure 1 The circuit of RS485 using MOS tube to realize automatic transmission and reception switching in the prior art is shown. Figure 1 In the circuit shown, the TX signal on the DI pin controls the RE and DE pins through a conversion circuit built by a MOS tube, so that when TXD=1, RE and DE=0 / when TXD=0, RE and DE=1, thereby realizing the switching control of the transmit and receive mode of the RS485 chip.

[0003] But if Figure 1 When the automatic transceiver switching circuit shown is actually used, the duty cycle on the AB signal line is smaller than the duty cycle on the TXD line, and the quality of signal transmission is poor. Utility Model Content

[0004] The present application provides an automatic transceiver switching circuit, which improves the signal transmission quality.

[0005] On the one hand, the present application provides an automatic transceiver switching circuit;

[0006] The circuit includes a serial communication chip, a first resistor, a second resistor, a first capacitor, a second capacitor, a switch tube and a diode;

[0007] The serial communication chip includes a signal receiving pin, a signal sending pin and a mode switching pin; the mode switching pin is connected to the power supply voltage terminal through the second resistor; the mode switching pin is also grounded through the switch tube;

[0008] The control end of the switch tube is grounded through the first capacitor; the control end of the switch tube is also connected to the signal sending pin through the first resistor; the control end of the switch tube is also connected to the signal sending pin through the diode.

[0009] In a possible implementation manner, the circuit further includes a second capacitor; and the mode switching pin is grounded through the second capacitor.

[0010] In a possible implementation, the switch tube is an NMOS tube;

[0011] The drain of the switch tube is connected to the power supply voltage terminal through the second resistor;

[0012] The source of the switch tube is grounded; the gate of the switch tube is connected to the source of the switch tube through the first capacitor.

[0013] In a possible implementation, the gate of the switch tube is connected to the anode of the diode; and the cathode of the diode is connected to the signal sending pin.

[0014] In a possible implementation, when the mode switching pin is at a high level, the serial communication chip sends data through the signal sending pin;

[0015] When the mode switching pin is at a low level, the serial communication chip receives data through the signal receiving pin.

[0016] In a possible implementation, the serial communication chip is RS485.

[0017] In a possible implementation, the serial communication chip further includes a first differential pin and a second differential pin; the circuit further includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor;

[0018] The first differential pin is connected to the power supply voltage terminal through the seventh resistor; the first differential pin is connected to the first signal line through the sixth resistor; the first differential pin is also connected to the second differential pin through the fifth resistor;

[0019] The second differential pin is grounded through the third resistor; the second differential pin is also connected to the second signal line through the fourth resistor.

[0020] The technical solution provided by this application may have the following beneficial effects:

[0021] The embodiment of the present application provides an automatic transceiver switching circuit, which includes a serial communication chip, a first resistor, a second resistor, a first capacitor, a switch tube and a diode; the serial communication chip includes a signal receiving pin, a signal sending pin and a mode switching pin; the mode switching pin is connected to the power supply voltage terminal through the second resistor; the mode switching pin is also grounded through the switch tube; the control end of the switch tube is grounded through the first capacitor; the control end of the switch tube is also connected to the signal sending pin through the first resistor; the control end of the switch tube is also connected to the signal sending pin through the diode. In the automatic transceiver switching circuit provided by the above scheme, the threshold level arrival time of the mode switching pin can be controlled by adjusting the resistance and capacitance parameters such as the first capacitor, the second capacitor, the first resistor, and the second resistor on the circuit, so as to realize the shaping of the enable signal of the mode switching pin, and then the online data duty cycle of the serial communication chip can be controlled to a certain extent, thereby improving the quality of signal transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 The present invention shows a circuit for realizing automatic transmission and reception switching of RS485 built by using MOS tube in the prior art.

[0024] Figure 2 The figure is a schematic diagram showing the structure of an automatic transceiver switching circuit according to an exemplary embodiment.

[0025] Figure 3 Shows Figure 2 The waveform diagram of the circuit shown when used on the RS485 chip. DETAILED DESCRIPTION

[0026] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0027] In the description of the embodiments of the present application, the term "corresponding" may indicate a direct or indirect correspondence between two items, or an association relationship between the two items, or a relationship between indication and being indicated, configuration and being configured, and the like.

[0028] Figure 2 exist Figure 1 The automatic transceiver circuit shown in the figure is further improved. Please refer to Figure 2 , which is a schematic diagram of a structure of an automatic transceiver switching circuit according to an exemplary embodiment. Figure 2 As shown, the circuit includes a serial communication chip U1, a first resistor R1, a second resistor R2, a first capacitor C1, a second capacitor C2, a switch tube Q1 and a diode D1;

[0029] The serial communication chip includes a signal receiving pin RO, a signal sending pin DI and a mode switching pin RE / DE; the mode switching pin RE / DE is connected to the power supply voltage terminal VCC through the second resistor R2; the mode switching pin RE / DE is also grounded through the switch tube Q1;

[0030] The control end of the switch tube Q1 is grounded through the first capacitor C1; the control end of the switch tube Q1 is also connected to the signal sending pin DI through the first resistor R1; the control end of the switch tube Q1 is also connected to the signal sending pin DI through the diode D1.

[0031] Optionally, in an embodiment of the present application, the serial communication chip is RS485, and the mode switching pin RE / DE in the serial communication chip is the RE / DE pin in the RS485 chip. When the mode switching pin is pulled high (high level), the serial communication chip is in chip sending mode, and when the mode switching pin RE / DE is pulled low (low level), it is in chip receiving mode.

[0032] In the above circuit structure, since the mode switching pin RE / DE is connected to the power supply voltage terminal VCC through the second resistor R2, and the mode switching pin RE / DE is grounded through the switch tube Q1, when the switch tube Q1 is turned off, the mode switching pin RE / DE is pulled high, and the serial communication chip is in the chip sending mode; when the switch tube Q2 is turned on, the mode switching pin RE / DE is pulled low, and the serial communication chip is in the chip receiving mode.

[0033] Therefore, in the embodiment of the present application, the switching between the receiving mode and the sending mode of the serial communication chip is controlled by the switch tube Q1.

[0034] In the embodiment of the present application, when a high level signal is sent from the signal sending pin on the serial communication chip, the first capacitor is charged through the first resistor R1, and since the positive electrode voltage of the diode is lower than the negative electrode voltage, the diode is in a cut-off state at this time;

[0035] When the first capacitor is fully charged, the switch tube Q1 meets the on state, the switch tube Q1 is turned on, and the mode switching pin RE / DE is instantly pulled low, and the serial communication chip is switched to the signal transmission mode. At this time, the full charge time of the first capacitor represents the delay of the serial communication chip switching to the signal transmission mode. By adjusting the parameters of the first resistor R1 and the first capacitor C1, the delay of the serial communication chip switching to the signal transmission mode can be controlled.

[0036] If the signal of the serial communication chip is sent, the signal sending pin on the serial communication chip is at a low level. At this time, the positive voltage of the diode is higher than the negative voltage, so the second diode is turned on. At this time, the charge in the first capacitor C1 will be instantly discharged through the diode D1, thereby turning off the switch tube Q1, so that the serial communication chip is switched to the sending mode.

[0037] Further, such as Figure 2 As shown, the circuit further includes a second capacitor C2, and the mode switching pin RE / DE is grounded through the second capacitor C2.

[0038] When the circuit also includes a second capacitor C2, when the switch tube Q1 is turned off, the second capacitor C2 begins to be charged by the second resistor R2, and the serial communication chip will not be switched to the sending mode instantly. When the second capacitor C2 is fully charged, the serial communication chip is switched to the sending mode and starts to send "0". Therefore, the parameters of the second capacitor C2 and the second resistor R2 can control the delay of the serial communication chip being switched to the signal sending mode.

[0039] Further, such as Figure 2 As shown, the switch tube is an NMOS tube;

[0040] The drain of the switch tube Q1 is connected to the power supply voltage terminal VCC through the second resistor R2;

[0041] The source of the switch tube Q1 is grounded; the gate of the switch tube Q1 is connected to the source of the switch tube Q1 through the first capacitor C1.

[0042] Further, such as Figure 2 As shown, the gate of the switch tube is connected to the anode of the diode; the cathode of the diode is connected to the signal sending pin.

[0043] Further, such as Figure 2 As shown, the serial communication chip further includes a first differential pin A and a second differential pin B; the circuit further includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7;

[0044] The first differential pin is connected to the power supply voltage terminal VCC through the seventh resistor R7; the first differential pin A is connected to the first signal line RS485_A through the sixth resistor R6; the first differential pin A is also connected to the second differential pin B through the fifth resistor R5;

[0045] The second differential pin B is grounded through the third resistor R3 ; the second differential pin B is also connected to the second signal line RS485_B through the fourth resistor R4 .

[0046] When the TXD signal on the signal sending pin DI sends 1, the first capacitor C1 is charged through the first resistor R1, and the positive electrode voltage of the diode D1 is lower than the negative electrode voltage, and the diode is in the cut-off state. At this time, the charging time of the first capacitor C1 can be adjusted by adjusting the resistance / capacitance value of the first resistor R1 and the first capacitor C1, thereby controlling the opening time of the switch tube Q1 (the time for the RE / DE pin to change from a high level to a low level). The switch tube Q1 will not be turned on until the voltage on the AB line is completely cut into a high state. At the same time, the RE / DE pin is directly grounded, and the voltage is instantly pulled to 0, ensuring that the signal receiving pin RO will not receive the previous signal "0" that has not been completed on the AB line.

[0047] When the TXD signal on the signal sending pin DI sends a 0, the positive electrode voltage of the diode D1 is higher than the negative electrode, the diode D1 is turned on, and the electricity of the first capacitor C1 will be instantly discharged through the diode D1, and the switch tube Q1 is turned off. At this time, the second capacitor C2 begins to be charged by the second resistor R2 (by adjusting the resistance / capacitance value here, the charging time of the second capacitor C2 can be controlled, and then the time for the RE / DE signal to change from 0 to 1 can be controlled, and finally the purpose of adjusting the duty cycle on the AB line is achieved) until the RE / DE threshold is reached, the RS485 chip switches to the sending mode and starts to send "0".

[0048] Figure 3 Shows Figure 2 The waveform diagram of the circuit shown is when it is used on the RS485 chip. Figure 3 As shown, by controlling Figure 2 The parameter values ​​of the resistors and capacitors shown can set a certain delay in the time for RE / DE (mode switching pin RE / DE) to switch from a high level to a low level, thereby ensuring that the first differential pin A is at a high level when switching to the receiving mode; the circuit can also shorten the time for RE / DE (mode switching pin RE / DE) to switch from a low level to a high level as much as possible, thereby preventing the receipt of a "0" signal.

[0049] In summary, the embodiment of the present application provides an automatic transceiver switching circuit, which includes a serial communication chip, a first resistor, a second resistor, a first capacitor, a second capacitor, a switch tube and a diode; the serial communication chip includes a signal receiving pin, a signal sending pin and a mode switching pin; the mode switching pin is connected to the power supply voltage terminal through the second resistor; the mode switching pin is also grounded through the switch tube; the control end of the switch tube is grounded through the first capacitor; the control end of the switch tube is also connected to the signal sending pin through the first resistor; the control end of the switch tube is also connected to the signal sending pin through the diode. In the automatic transceiver switching circuit provided by the above scheme, the threshold level arrival time of the mode switching pin can be controlled by adjusting the resistance and capacitance parameters such as the first capacitor, the second capacitor, the first resistor, and the second resistor on the circuit, so as to realize the shaping of the enable signal of the mode switching pin, and then the online data duty cycle of the serial communication chip can be controlled to a certain extent, thereby improving the quality of signal transmission.

[0050] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the utility model disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0051] It should be understood that the present application is not limited to the exact construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims

1. An automatic transceiver switching circuit, characterized in that: The circuit includes a serial communication chip, a first resistor, a second resistor, a first capacitor, a switch tube and a diode; The serial communication chip includes a signal receiving pin, a signal sending pin and a mode switching pin; the mode switching pin is connected to the power supply voltage terminal through the second resistor; the mode switching pin is also grounded through the switch tube; The control end of the switch tube is grounded through the first capacitor; the control end of the switch tube is also connected to the signal sending pin through the first resistor; the control end of the switch tube is also connected to the signal sending pin through the diode.

2. The circuit according to claim 1, characterized in that The circuit also includes a second capacitor; the mode switching pin is grounded through the second capacitor.

3. The circuit according to claim 1, characterized in that The switch tube is an NMOS tube; The drain of the switch tube is connected to the power supply voltage terminal through the second resistor; The source of the switch tube is grounded; the gate of the switch tube is connected to the source of the switch tube through the first capacitor.

4. The circuit according to claim 3, characterized in that The gate of the switch tube is connected to the anode of the diode; the cathode of the diode is connected to the signal sending pin.

5. The circuit according to claim 1, characterized in that When the mode switching pin is at a high level, the serial communication chip sends data through the signal sending pin; When the mode switching pin is at a low level, the serial communication chip receives data through the signal receiving pin.

6. The circuit according to any one of claims 1 to 5, characterized in that: The serial communication chip is RS485.

7. The circuit according to claim 6, characterized in that The serial communication chip further includes a first differential pin and a second differential pin; the circuit further includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor; The first differential pin is connected to the power supply voltage terminal through the seventh resistor; the first differential pin is connected to the first signal line through the sixth resistor; the first differential pin is also connected to the second differential pin through the fifth resistor; The second differential pin is grounded through the third resistor; the second differential pin is also connected to the second signal line through the fourth resistor.

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