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Asynchronous serial communication method based on electric current loop

An asynchronous serial communication and current loop technology, applied in the direction of electrical digital data processing, instruments, etc., can solve the problem of no essential difference, achieve strong anti-interference ability, high performance and price ratio, and improve the effect of long-distance transmission ability

Active Publication Date: 2009-09-02
TRAFFIC CONTROL TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Figure 10 A schematic diagram of the principle of realizing the asynchronous serial communication mode 2 by the current loop is given, and the Figure 9 The difference is that the constant current source is generated by the receiver, but there is no essential difference in the principles of sending and receiving

Method used

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  • Asynchronous serial communication method based on electric current loop
  • Asynchronous serial communication method based on electric current loop
  • Asynchronous serial communication method based on electric current loop

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0033] Such as figure 1 Shown is the implementation block diagram of current loop asynchronous serial communication applied to microprocessor communication.

[0034] A constant current source is generated internally by the current loop asynchronous serial sender to provide a constant current signal to the outside. The current signal goes through "constant current source→TTY sending positive→receiving load→TTY sending negative→photocoupler" to form a complete current loop. The entire transmitting part is controlled by the serial transmitting terminal (TXD) of the universal asynchronous serial device (UART). The transmitting signal controls the on and off of the current loop by controlling the on and off of the photocoupler, so that the receiving load or A specific current passes (logic 1) or no current passes (logic 0). It should be noted that when the photocoupler is used to realize the on-off control of the current loop, negative logic may be used, that is, the high level is cut...

Embodiment 2

[0040] Such as image 3 Shown is another implementation block diagram of the current loop asynchronous serial communication applied to the microprocessor. In this embodiment, the power and ground of the current loop for communication transmission are both on the receiver side, and are electrically isolated from the logic circuits on both sides of the sender and receiver. Therefore, the constant current source circuit is generated by the asynchronous serial receiver of the current loop, and the current signal passes through "constant current source→receiving load→TTY receiving positive electrode→photocoupler→TTY receiving negative electrode→ground" to form a complete current loop. The entire transmitting part is still controlled by the serial transmitting terminal (TXD) of the universal asynchronous serial device (UART). At the same time, the receiver uses the voltage value on the load to send it to the serial device of the asynchronous serial device through the voltage comparator ...

Embodiment 3

[0043] Such as Figure 5 Shown as the current loop asynchronous serial communication 20mA constant current source specific implementation circuit diagram. The LM4040 in the picture is a high-precision micro-power voltage reference chip that provides a stable 5V reference voltage. Therefore, the voltage at the non-inverting input of the operational amplifier U1A is 19V. According to the "virtual break" characteristic of the operational amplifier, the current at the inverting input of U1A is 0. Therefore, the current on the resistor R2 is equal to the current flowing into the emitter of the transistor P1, which is assumed to be I. The voltage at the inverting input terminal of the operational amplifier U1A is U_=24V-R2×I. When the transistor P1 is in the off state, the current I on the resistor R2 is 0, so the voltage U_ at the inverting input terminal of the operational amplifier U1A is 24V. This voltage is greater than the voltage at the non-inverting input, so the output of the o...

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Abstract

The invention discloses an asynchronous serial communication method based on a current loop, which belongs to the technical field of serial communication. First, a constant current source is used as the current for communication transmission, and then a photoelectric coupler is used to control the communication of the current loop with a voltage signal. In this way, the voltage serial communication signal is used to control the current loop logic, and the transmission of the current loop asynchronous serial communication is realized. At the same time, the current-voltage conversion circuit and the threshold judgment circuit are implemented, which can convert the current loop logic into the corresponding TTL level logic, thereby realizing the reception of the current loop asynchronous serial communication. The invention can realize long-distance serial communication, has strong anti-interference ability and low bit error rate. At the same time, it has a high performance-price ratio.

Description

Technical field [0001] The invention relates to an asynchronous serial communication method based on a current loop, which is applied to long-distance communication between microprocessors, computers, or between computers and microprocessors, and is particularly applied to situations with complex electromagnetic environments, and belongs to the technical field of serial communication . Background technique [0002] Serial communication is a widely used communication method between computers and is used in various occasions. At present, most of the widely used microcontrollers (such as MCS51 series microcontrollers) have asynchronous serial communication interfaces (UART), or asynchronous serial communication interface chips (such as INS8250) can be easily used to expand asynchronous serial communication interfaces. Line communication interface. In addition, computers above 80286 are also equipped with RS232C standard serial communication interfaces. However, this voltage serial c...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F13/38
Inventor 袁磊张建明李开成
Owner TRAFFIC CONTROL TECH CO LTD