CN102117254A - Embedded-system-based asynchronous data receiving method - Google Patents

Abstract

The invention relates to an embedded-system-based asynchronous data receiving method, which belongs to the field of electronic equipment control. The method comprises the following steps that: a timing interval of a timer is set according to the baud rate of an upper computer; an external interrupt port of a system serves as a data receiver connected with the upper computer, and triggers the external interrupt of the system when receiving a data start bit from the upper computer, the system uses the external interrupt port as an ordinary input/output (I/O) port, and simultaneously the timer starts timing; the system performs sampling on the external interrupt port at a certain time interval, and stores obtained data; and when a data stop bit is obtained from the upper computer in the sampling, the system finishes the external interrupt, the timer stops timing, and the system stops using the external interrupt port as the ordinary I/O port. In the method, asynchronous data reception can be realized simply only by the external interrupt port and the timer.

Description

Method based on the asynchronous reception of Implementation of Embedded System data

 

Technical field:

The present invention relates to a kind of method that realizes the asynchronous reception of data, relate to a kind of method specifically, belong to electronic equipment control field based on the asynchronous reception of Implementation of Embedded System data.

Background technology:

The asynchronous reception of data is a kind of communication mode that is in daily use.Asynchronous communication is when sending signal, and the time interval between the signal that is sent can be arbitrarily.Certainly, receiving end must be carried out the preparation of reception constantly, if the power supply of receiving end main frame does not add that all it is just nonsensical that transmitting terminal sends character so, because receiving end can't receive at all.Transmitting terminal is the proceed-to-send signal character at any time, therefore must add mark at the beginning and the end position of each character, promptly adds start bit and position of rest, so that receiving end can correctly be received each character.The benefit of asynchronous communication is that communication facilities is simple, cheap.

Existing embedded system mainly is the SCI serial communication module that utilizes system's master chip in order to realize the asynchronous reception of data, carries out some simple parameters and sets and realize.But this design needs special SCI module or RXD port, if system just can't not carry out, is subjected to the restriction ratio of hardware condition bigger.

Summary of the invention:

Technical matters to be solved by this invention overcomes the deficiency of above-mentioned prior art exactly, and a kind of method that realizes the asynchronous reception of data based on the external interrupt port of embedded system is provided.

In order to solve the problems of the technologies described above, the present invention adopts following technical scheme:

A kind of method based on the asynchronous reception of Implementation of Embedded System data comprises the steps,

(1) according to the baud rate of host computer, the timing interval of delta t of setting timer is the inverse of host computer baud rate;

(2) with the external interrupt port of system as the data receiver that is connected with host computer, when it receives the data start bit that host computer sends, the external interrupt of triggering system, system uses the external interrupt port as common I/O mouth, and timer picks up counting simultaneously;

(3) system took a sample once from the external interrupt port every the Δ t time, and the data that obtain are done to preserve processing;

(4) when sampling obtains data position of rest that host computer sends, the system finishing external interrupt, timer stops timing, and stops the external interrupt port is used as common I/O mouth.

The invention has the beneficial effects as follows: after using the inventive method,,, just can realize the asynchronous reception of data as long as 1 external interrupt port and 1 timer are arranged even embedded system does not have special SCI module or RXD port.Not only easy, stable, and cost is low, and real-time is good.

Description of drawings:

Fig. 1 is the FB(flow block) of the embodiment of the invention 1;

Fig. 2 is the procedure chart that the inventive method receives 1 frame data.

Embodiment:

Embodiment 1, and referring to Fig. 1, a kind of method based on the asynchronous reception of Implementation of Embedded System data comprises the steps,

(1) according to the baud rate of host computer, the timing interval of delta t of setting timer is the inverse of host computer baud rate, is 9600Hz such as the baud rate of this routine host computer, and Δ t is exactly 1/9600=104 μ s so.

(2) with the external interrupt port of system as the data receiver that is connected with host computer, when it receives the data-signal that host computer sends, the external interrupt of triggering system, system uses the external interrupt port as common I/O mouth, this moment, system carried out analysis and judgement to data-signal, if the data start bit, timer picks up counting so, otherwise the system finishing external interrupt is external interrupt ports-settings waiting signal.

(3) if the data start bit, system every the Δ t time from the sampling of external interrupt port once, and the data that obtain are done to preserve handle.When sampling obtained data position of rest that host computer sends, timer stopped timing, stops the external interrupt port is used as common I/O mouth, and is external interrupt ports-settings waiting signal; When sampling obtain be not host computer send the data position of rest time, timer continues timing.

The process that wherein specifically receives 1 frame data as shown in Figure 2, suppose totally 11 of frame data, 1 start bit+8 bit data positions+1 bit parity check position+1 position of rest, when the external interrupt port receives the data start bit, timer picks up counting, and the external interrupt port used as common I/O mouth, utilize system delay and use timer every 104 μ s timing samplings, can accurately take a sample to the high-low level (1 or 0) of input, when sampling obtains data position of rest that host computer sends, timer stops timing, stops the external interrupt port is used as common I/O mouth, thus the asynchronous reception of realization data.

Claims (1)

1. method based on the asynchronous reception of Implementation of Embedded System data is characterized in that: comprises the steps,

(1) according to the baud rate of host computer, the timing interval of delta t of setting timer is the inverse of host computer baud rate;

(2) with the external interrupt port of system as the data receiver that is connected with host computer, when it receives the data start bit that host computer sends, the external interrupt of triggering system, system uses the external interrupt port as common I/O mouth, and timer picks up counting simultaneously;

(3) system took a sample once from the external interrupt port every the Δ t time, and the data that obtain are done to preserve processing;

(4) when sampling obtains data position of rest that host computer sends, the system finishing external interrupt, timer stops timing, and stops the external interrupt port is used as common I/O mouth.

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