CN106209678A - MODBUS message frame method of reseptance for DSP/BIOS - Google Patents

Abstract

The invention discloses a kind of MODBUS message frame method of reseptance for DSP/BIOS, based on DSP/BIOS software desk Implementation, flow process and message frame handling process is received including message frame, wherein message frame receives the realization of process selecting SCI hardware interrupts thread, and message frame handling process selection cycle traps thread realizes.Message frame processes cycle traps thread elapsed time clock and is driven by system clock, and makes its clock cycle value equal to MODBUS message frame time interval, and when elapsed time clock adds up until being equal to the clock cycle, inbound message frame processes traps thread.The present invention uses in system clock replacement prior art and determines character pitch time the method accurately distinguishing two message frames with intervalometer, can effectively save the hardware resource of microprocessor, lower the automation control system peripheral hardware resource requirement to microprocessor.

Description

MODBUS message frame receiving method for DSP/BIOS

technical field

The invention relates to a method for receiving a MODBUS message frame, in particular to a method for receiving a MODBUS message frame for DSP/BIOS.

Background technique

Modbus, invented by Modicon in 1979, is the world's first real bus protocol for industrial field. It has become the communication protocol standard in the industrial field and has been widely used. Determining the idle time of the communication line and thus accurately distinguishing the two message frames has always been an important problem that must be solved in the MODBUS communication process. In the prior art, the communication between the microprocessor and the MODBUS equipment is all realized by the method of timer interruption, that is, the timer timing value is equal to the time interval between message frames, and the current value of the timer is reset when entering the SCI interrupt program each time. Timing value, when entering the timer interrupt program, it means that the current message frame has been transmitted. This technology can be seen in "Design of Mining DTU Test System Based on STM32F103 and MODBUS" published in "Coal Mining Machinery" in 2013, " Communication between PC and dsPIC6014 processor based on MODBUS protocol", "Research on master-slave communication between S7-200 series PLC and single-chip microcomputer based on Modbus protocol" published in "Laboratory Research and Exploration" in 2012, etc. Although this method is simple and easy to implement, it takes up valuable timer resources of the microprocessor, making its hardware resources not effectively utilized, and also increases the peripheral resource requirements of the automatic control system for the microprocessor.

Contents of the invention

In order to solve the above-mentioned problem that the existing MODBUS communication technology occupies microprocessor timer resources, the present invention provides a MODBUS message frame receiving method for DSP/BIOS.

To achieve the above object, the present invention adopts the following technical methods:

A kind of MODBUS message frame receiving method for DSP/BIOS, realizes based on DSP/BIOS software platform, comprises message frame receiving flow and message frame processing flow, described message frame receiving flow selects SCI hardware interrupt thread to realize, described message frame Processing flow selection cycle soft interrupt thread implementation.

Further, the specific running process of the SCI hardware interrupt thread is:

(1) The serial port enters the SCI hardware interrupt thread after receiving 1 character data;

(2) Reset message frame processing cycle soft interrupt thread timing clock;

(3) Read the received data and save it to the member pointed to by the current member number value in the received frame array;

(4) Add 1 to the current member number of the receiving frame array;

(5) Return from the SCI hardware interrupt thread;

Further, the timing clock of the message frame processing cycle soft interrupt thread is driven by the system clock.

Further, the message frame processing cycle soft interrupt thread clock cycle is the time required to transmit 3.5 character data.

Furthermore, the message frame processing cycle soft interrupt thread adopts a single operation mode.

Further, the specific running process of the soft interrupt thread of the message frame processing cycle is:

(1) When the soft interrupt thread timing clock value of the message frame processing cycle is equal to the set clock cycle, it enters into operation;

(2) The current member number of the receiving frame array is cleared;

(3) data processing;

(4) Send a response message frame;

(5) Return from the message frame processing cycle soft interrupt thread.

Compared with the prior art, the present invention adopts the system clock to replace the prior art method of determining character interval time and accurately distinguishing two message frames by a timer, which can effectively save the hardware resources of the microprocessor and reduce the impact of the automatic control system on the microprocessor. The device's peripheral resource requirements.

Description of drawings

Fig. 1 is the message frame receiving flowchart of the embodiment of the present invention;

Fig. 2 is a message frame processing flowchart of an embodiment of the present invention;

Fig. 3 is the connection diagram of TMS320F28335 type DSP and MODBUS equipment in the specific embodiment.

detailed description

The present invention will be further described below in conjunction with accompanying drawings and examples.

As shown in Fig. 1 and Fig. 2, a kind of MODBUS message frame receiving method for DSP/BIOS, realizes based on DSP/BIOS software platform, comprises message frame receiving flow and message frame processing flow, described message frame receiving flow selects SCI The hardware interrupt thread is implemented, and the message frame processing flow is implemented by a periodic soft interrupt thread.

Specifically, the specific running process of the SCI hardware interrupt thread is:

(1) The serial port enters the SCI hardware interrupt thread after receiving 1 character data;

(2) Reset message frame processing cycle soft interrupt thread timing clock;

(3) Read the received data and save it to the member pointed to by the current member number value in the received frame array;

(4) Add 1 to the current member number of the receiving frame array;

(5) Return from the SCI hardware interrupt thread.

Specifically, the message frame processing cycle soft interrupt thread timing clock is driven by the system clock.

Specifically, the message frame processing cycle soft interrupt thread clock cycle is the time required to transmit 3.5 character data.

Specifically, the message frame processing cycle soft interrupt thread adopts a single-run mode.

Specifically, the specific running process of the soft interrupt thread of the message frame processing cycle is:

(1) When the soft interrupt thread timing clock value of the message frame processing cycle is equal to the set clock cycle, it enters into operation;

(2) The current member number of the receiving frame array is cleared;

(3) data processing;

(4) Send a response message frame;

(5) Return from the message frame processing cycle soft interrupt thread.

DSP is the abbreviation of digital signal processor. In this example, the DSP processor of C2000 series and model TMS320F28335 produced by TI company is selected. TMS320F28335 is connected with MODBUS equipment through RS232 (see Figure 3). The baud rate is 9600b/s, and the communication mode is Adopt MODBUS RTU, the data transmission format is 1bit start bit, 8bit data bit, 1bit stop bit, no parity bit.

DSP/BIOS is a size-cuttable real-time multitasking operating system kernel specially designed and developed by TI for its TMS320C6000TM, TMS320C5000TM and TMS320C28xTM series DSP platforms. DSP supports four threads with different priorities, which are arranged in order of priority from high to low, namely hardware interrupt (HWI), software interrupt (SWI), task (TSK) and background thread (IDL). Periodic function (PRD) is a special software interrupt. When its timing clock is equal to the set clock period value, it enters the ready state. The main configuration parameters of its example are:

(1) period: Periodic function clock period value. When the current clock timing value of the periodic function reaches the set clock period value, it enters the ready state. The timing clock can be driven by the system clock, or add 1 after calling the PRD_tick function;

(2) mode: Periodic function operation mode, there are two types of continuous operation (continuous) and single-shot (one-shot).

The API function and function thereof that the present invention mainly uses are as follows:

(1) PRD_start: It is used to start a timing clock of a periodic function, and the periodic function enters operation after starting and waiting for the set clock cycle. If PRD_start is called again before the current clock count value of the periodic function reaches the set clock cycle value, the current clock count value will restart from zero.

In the DSP/BIOS program of TMS320F28335, the message frame receiving process is created as an SCI hardware interrupt thread, and the message frame processing process is created as a periodic soft interrupt thread. Wherein the realization of the present invention needs to set the message frame processing thread as a single trigger mode, and its clock cycle value (period) is set to the minimum time interval between two message frames or data packets in the MODBUS communication, i.e. 3.5 character data transmission time, Its timing clock is driven by the system clock. When the baud rate is 9600b/s and the transmission format is 10bit, the message frame processing cycle soft interrupt thread clock cycle value is as follows:

$\frac{\mathrm{<span\; class="notranslate">\; 3.5</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; 9600</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 1000</span>}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 3.7</span>}\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; ,</span>$

When the serial port receives 1-character data transmitted by the MODBUS device, the DSP/BIOS program enters the message frame receiving thread. In this thread, first call the PRD_start function to start the timing clock of the message frame processing PRD thread, then read the data from the SCI receiving register and save it to the receiving frame array, and return after adding 1 to the current member number of the receiving frame array. During the transmission process of the same data packet, the DSP/BIOS program constantly repeats the above process. Since the two-character data transmission interval in a data packet is less than the clock cycle value of the message frame processing cycle soft interrupt thread, and calls PRD_start to reset the current timing clock value of the message frame processing cycle soft interrupt thread when entering the SCI hardware interrupt thread each time, the DSP The /BIOS program will not enter the message frame processing cycle soft interrupt thread. After the current message frame transmission is completed, the idle time of the communication line is greater than the clock cycle value of the message frame processing cycle soft interrupt thread, and the thread starts running after the current timing clock reaches the clock cycle value.

The message frame processing cycle soft interrupt thread is responsible for processing the received message frame. First reset the current member number of the receive frame array to receive the next message frame. Then process the message frame, such as CRC check, extract valid data in the data field of the message frame, and so on. If TMS320F28335 is a MODBUS slave, it will return from this thread after sending the corresponding response message frame according to the interpretation of valid data; if it is a MODBUS master, it will return directly.

The above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (6)

1. a kind of MODBUS message frame receiving method for DSP/BIOS, realizes based on DSP/BIOS software platform, comprises message frame receiving process and message frame processing flow, it is characterized in that: message frame receiving process selects SCI hardware interrupt thread to realize, The message frame processing flow is implemented by selecting a periodic soft interrupt thread. 2. a kind of MODBUS message frame receiving method that is used for DSP/BIOS according to claim 1, is characterized in that, described SCI hardware interrupt thread concrete running process is: (1) The serial port enters the SCI hardware interrupt thread after receiving 1 character data; (2) Reset message frame processing cycle soft interrupt thread timing clock; (3) Read the received data and save it to the member pointed to by the current member number value in the received frame array; (4) Add 1 to the current member number of the receiving frame array; (5) Return from the SCI hardware interrupt thread. 3. the MODBUS message frame receiving method that is used for DSP/BIOS according to claim 1 is characterized in that: message frame processing cycle soft interrupt thread timing clock is driven by system clock. 4. the MODBUS message frame receiving method that is used for DSP/BIOS according to claim 1 is characterized in that: message frame processing cycle soft interrupt thread clock cycle is the time required for transmission of 3.5 character data. 5. the MODBUS message frame receiving method that is used for DSP/BIOS according to claim 1 is characterized in that: message frame processing cycle soft interrupt thread adopts single run mode. 6. the MODBUS message frame receiving method that is used for DSP/BIOS according to claim 1, is characterized in that, described message frame processing cycle soft interrupt thread concrete running process is: (1) When the soft interrupt thread timing clock value of the message frame processing cycle is equal to the set clock cycle, it enters into operation; (2) The current member number of the receiving frame array is cleared; (3) data processing; (4) Send a response message frame; (5) Return from the message frame processing cycle soft interrupt thread.