Claims:1. A method for automatically detecting baud rate value in at least one communication module when receiving data messages from at least one remote terminal device, wherein said method comprising:
pre-setting, said communication module to at least one default baud rate value, and thereby initiating said communication module to receive said data messages from said remote terminal device by means of a receive communication link;
receiving, by a processing unit in said communication module, data frames corresponding to said data messages and initiating data processing method for determining if said data frames are valid or invalid; and
simultaneously monitoring, by an input port of said processing unit, edge transition corresponding to said data frames, and thereby generating at least one edge triggered interrupt, wherein said input port coupled to said receive communication link;
detecting, by said processing unit, if said edge is a first edge or a second edge of said data frame, wherein if said edge is a first edge, triggering at least one timer at said first edge, wherein if edge is a second edge, enable record of timer count between said first edge and said second edge and thereby triggering said timer, wherein said timer count generates a baud rate value;
comparing, by said processing unit, said baud rate value with said default baud rate value of said communication module;
setting, by said processing unit, the baud value of said communication module to the default baud rate value if said baud rate value corresponds to said default baud rate value, else setting the baud value of said communication module according to the generated baud rate value.

2. The method as claimed in claim 1, wherein said communication module coupled to said remote terminal device by means of at least one serial communication protocol, preferably selected as RS-485 differential bus.

3. The method as claimed in claim 1, wherein during said data processing method, if said data frames are valid, then generating, by said processing unit, response frames corresponding to said data frames, and thereby transmitting said response frame to said remote terminal device, else discarding, by said processing unit, said data frames.

4. The method as claimed in claim 1, wherein said edge transition of said data frames corresponds to high-to-low or low-to-high edge.

5. The method as claimed in claim 1, wherein said data frame comprises at least one start bit, 8 bits of data and at least one stop bit.

6. The method as claimed in claim 1-5, wherein recording of said timer count stores a transition time between said first and second edge in said data frame.

7. The method as claimed in claim 6, wherein said timer count stores minimum transition time for said data frame to determine time period of a single bit in said data frame, wherein said single corresponds to the reciprocal of said baud rate value.

8. A data communication module configured to receive data messages from a remote terminal device and operating the method as claimed in claims 1-7, said data communication module comprising:
at least one converter module configured to translate said data messages from said remote terminal device into data messages compatible to said communication module;
at least one processing unit integrated with Universal Asynchronous Receiver/Transmitter (UART) to receive/transmit data messages, by using at least two communication link, from/to said converter module, and said processing unit comprises at least one input port coupled to one of the said communication link to monitor received data messages and determine level edge transitions;
wherein said processing unit configured to:
detect if said edge is a first edge or a second edge, wherein if said edge is a first edge, trigger at least one timer at said first edge, wherein if edge is a second edge, enable record of timer count between said first edge and said second edge to generate a baud rate value;
compare, said baud rate value with a default baud rate value pre-set in said communication module; and thereby if said baud rate value corresponds to said default baud rate value, set the baud value of said communication module according to default baud rate value, else set the baud value of said communication module according to the generate baud rate value.
, Description:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to communication protocols and devices, and more particularly relates to a method for automatically detecting baud rate in Modbus remote terminal unit (RTU) based communication for use in an electrical switching devices.

BACKGROUND

[002] An electronic trip unit (ETU) senses the current flowing through a feeder or a motor where the circuit breaker is installed. The ETU can provide various types of protections from electrical faults such as thermal overload, short circuit, earth fault, and the like. Higher end electronic trip units also add functionalities such as energy metering, trip records along with different type of advanced protections. It also can detect the position of circuit breaker and counters for breaker operations.

[003] An electronic trip unit with advanced functionalities has lot of configuration parameters and status information which needs a proper user interface. Therefore generally higher end trip units have a display module with keypad or touchscreen. It can be used to configure various settings for protections and other functions and also to view status information such as trip records, breaker status, fault counters and the like.

[004] An Industry will have many such circuit breakers installed at various different places. Hence, the configuration process consumes lot of time and resources. Hence there is a communication module provided as accessory to the electronic trip unit which provides remote access to all the information and configuration parameters. All the breakers and their information can be monitored from a remotely located control room where a SCADA system is installed. Tasks like configuring various settings of different circuit breakers, monitor metering values, generate alarms, check records, execute remote commands can be performed with minimum efforts. It can be integrated with industrial automation systems.

[005] Typically, the communication module follows various serial wired or wireless protocols that includes Modbus RTU, TCP/IP, Profibus, and the like. Modbus RTU has been a very popular communication protocol in industry as it needs RS485 as physical medium which is relatively cost effective and simpler in installations. Modbus RTU is a serial protocol which has Master-Slave system. The remote station or SCADA acts as Master and communication modules for individual circuit breakers act as Modbus Slaves with different Slave IDs.

[006] Modbus RTU Communication module has its communication parameters such as Slave ID, Parity, Stop bit and Baud rate which need to be configured as per the configuration of the Modbus Master. Baud rate is a very important parameter which is measured in number of bits per second. Generally Modbus RTU supports baud rates from ‘1200’ to higher baud rate such as 115.2 kbps.

[007] However, as per Modbus RTU specifications, master and the slave both should be properly configured for the same desired baud rate. If master wants to change the baud rate then the baud rate configuration of all the Slave IDs also needs to be changed. There is also a possibility that all the slaves may not support a particular baud rate hence it becomes difficult to configure baud rates or change baud rate setting of the Modbus Master. This introduces rigidness in configuration process for Modbus RTU communication system.

[008] Reference is made to Chinese patent application CN104052579A which gives an automatic baud rate matching process for Modbus RTU communication modules. As per the proposed process when the Modbus slave device receives certain number of error message packets from the master, it changes its baud rate to the next available setting. In this way it will keep on going into the baud rate matching process till valid message is received from master. This method manages to detect the baud rate but requires high amount of processing. Also the delay of detecting the correct baud rate is high because it’ll keep on trying with different baud rates to match it with the baud rate setting of the master. In the case when multiple slaves are connected with different baud rate settings, each slave will receive error message packets during communication of the other slave. Hence the matching process runs very frequently which results into high processor usage and also hampers the communication timings.

[009] Reference is also made to a non-patent document H8/300L which is an application note by Renesas. The document describes a software implementation for automatic baud rate detection for establishing communication link between two devices. It is a pure software implementation description. The baud rate detection method is generic for two devices communicating on serial lines. It does not talk about any specific system or application. As per the implementation, there are set of pre-defined characters which are known to both master and the slave. The master sends pre-defined characters to the slave with a particular baud rate. The slave tries to sample the data with one baud rate and checks if it matches with the pre-defined character then it means that it is sampling with correct baud rate. If the sampled data is not matched with those characters then the slave tries sampling with different baud rate. Hence it is a trial and error method where every baud rate setting for sampling is tried till a sampled data matched with the pre-defined character is obtained. Also here there is a need for a pre-defined character to be sent for baud rate detection. Hence the master has this work to do about deciding when to start baud rate detection. This implementation is completely separate software process with special requirements of pre-defined characters and the process is not integrated along with the main application

[0010] Thus, in view of the drawbacks of the prior art, there exist a dire need to a method of automatic baud rate detection for Modbus RTU communication module which enhances the flexibility of the Modbus RTU communication system with respect to the baud rate configurations with time efficient minimalistic processing.

SUMMARY OF THE INVENTION

[0011] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0012] An object of the present invention is to provide a method for automatically detecting baud rate in Modbus remote terminal unit (RTU) based communication for use in electrical switching devices.

[0013] Accordingly to one aspect, the present invention provides a method for automatically detecting baud rate value in at least one communication module when receiving data messages from at least one remote terminal device, wherein said method comprising:
• pre-setting, said communication module to at least one default baud rate value, and thereby initiating said communication module to receive said data messages from said remote terminal device by means of a receive communication link;
• receiving, by a processing unit in said communication module, data frames corresponding to said data messages and initiating data processing method for determining if said data frames are valid or invalid;
• simultaneously monitoring, by an input port of said processing unit, edge transition corresponding to said data frames, and thereby generating at least one edge triggered interrupt, wherein said input port coupled to said receive communication link;
• detecting, by said processing unit, if said edge is a first edge or a second edge of said data frame, wherein if said edge is a first edge, triggering at least one timer at said first edge, wherein if edge is a second edge, enable record of timer count between said first edge and said second edge and thereby triggering said timer, wherein said timer count generates a baud rate value;
• comparing, by said processing unit, said baud rate value with said default baud rate value of said communication module;
• setting, by said processing unit, the baud value of said communication module to the default baud rate value if said baud rate value corresponds to said default baud rate value, else setting the baud value of said communication module according to the generated baud rate value.

[0014] In the second aspect, there is provided a data communication module configured to receive data messages from a remote terminal device and operating the method as mentioned, said data communication module: at least one converter module configured to translate said data messages from said remote terminal device into data messages compatible to said communication module; at least one processing unit integrated with Universal Asynchronous Receiver/Transmitter (UART) to receive/transmit data messages, by using at least two communication link, from/to said converter module, and said processing unit comprises at least one input port coupled to one of the said communication link to monitor received data messages and determine level edge transitions;
wherein said processing unit configured to:
• detect if said edge is a first edge or a second edge, wherein if said edge is a first edge, trigger at least one timer at said first edge, wherein if edge is a second edge, enable record of timer count between said first edge and said second edge to generate a baud rate value;
• compare, said baud rate value with a default baud rate value pre-set in said communication module; and thereby
• set the baud value of said communication module according to default baud rate value if said baud rate value corresponds to said default baud rate value, else set the baud value of said communication module according to the generates baud rate value.

[0015] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0016] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0017] Figure 1 illustrates the system block diagram according to one embodiment of the present invention.
[0018] Figure 2 illustrates the basic internal architecture of the communication module according to one embodiment of the present invention.
[0019] Figure 3 illustrates an internal process flow of the communication module according to one embodiment of the present invention.
[0020] Figure 4 illustrates an automatic baud rate detection process according to one embodiment of the present invention.

[0021] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0022] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0023] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0024] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0025] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0026] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0027] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0028] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0029] It is also to be understood that the term “module” is used in the specification to indicate an apparatus, unit, component and the like. The term “means” when used in the specification is taken to specify the mode by which desired result is achieved.

[0030] The present invention can be implemented with an electrical switching system that may include but not limited to, circuit breakers or thermo-magnetic breaker, molded case circuit breaker (MCCB) residual circuit breaker (RCB), earth leakage circuit breaker (ELCB) and the like.

[0031] In one unit, an electronic trip is communicably couple to the communication module. The electronic trip unit is the primary processing unit to provide the primary features that may include but not limited to protections, record keeping, updating status information or any combination thereof. The communication module is responsible to act as Modbus Slave for the remote terminal unit such as SCADA or the Modbus master, to give access to the information in the trip unit. The communication module can also be integrated into the electronic trip unit as one single embedded system. A separate communication module provided as an accessory with the main electronic trip unit adds flexibility to the application and the user.

[0032] In one embodiment, as shown in Figure 1, the communication module can be a separate entity which is connected to the trip unit on an internal bus for communication. There is a remote terminal device or control room where the SCADA system is installed which is connected to the communication module using at least one communication such as RS-485 differential bus. The SCADA is the Modbus Master following Modbus RTU protocol and the communication module acts as a Modbus slave. Slave ID of the communication module can be configured using different type of user interfaces such as a DIP switch, local display unit and the like.

[0033] In one embodiment, reference is made to figure 2 which shows the basic internal architecture of the communication module. It consists of a microcontroller which is the main processing unit of the module. The microcontroller has an integrated UART engine which has 2 lines for serial communication i.e. ‘Tx’ and ‘Rx’. There is a TTL-to-RS485 converter module which is normally an analog integrated circuit (IC). This converter module translates the TTL signals of Tx and Rx into RS-485 differential bus which enables the microcontroller to communicate with the Modbus Master. As shown in the figure 2 the Rx signal which shows the data received from the Modbus Master is also connected to an input port of the microcontroller. The input port pin is continuously monitored by the microcontroller. The timings of level transitions of the Rx signal are analyzed to determine the baud rate at which Master is sending the data.

[0034] In one embodiment, reference is made to figure 3 which shows the internal process flow of the communication module. After the module is powered on, it first undergoes configuration process to configure its functional parameters. Baud rate is one of the main configuration parameter for Modbus serial communication. It starts with a preset baud rate value and goes into receiving mode as the main process starts. When the Modbus Master sends a message, the data bytes are received based on sampling with preset baud rate. According to the data processing if a valid data frame is detected, then an appropriate response frame is prepared and sent to the Modbus Master. Otherwise the received bytes are discarded. There is another process executed in parallel to monitor the ‘Rx’ signal through an input port pin. This process is the novel method for detecting the baud rate automatically shown inside the dotted box in figure 3. There is a timing measurement module which analyzes the level transitions of the ‘Rx’ Signal continuously as the data bytes are received. With the timing analysis it is detected if the baud rate has been changed or not and the communication module is re-configured for the new baud rate if detected. The method of automatic baud rate detection is a parallel process and hence it does not cause any undesired delay to affect the basic Modbus data processing and response generation.

[0035] In one embodiment, reference is made to figure 4, the automatic baud rate detection process is explained with detail. The input port of the microcontroller can be configured to generate an edge-triggered interrupt. When an edge is detected on ‘Rx’ signal (High-to-Low or Low-to-High), an interrupt is generated. On the basis of the current state of Modbus reception module it is detected whether the current detected edge is the first edge of a Modbus Data Frame or not. This is the syncing process which is responsible to sync the baud rate detection process with the received Modbus data. At the first edge, a timer is started. When the next edge is detected, the timer count is recorded to know the transition time between edges and the timer is restarted. In this way the process keeps track of transition time between every consecutive edge of in a data frame. Every byte in a data frame at least has one start bit, 8 bits of data and one or two stop bits. Hence the process stores the minimum transition time for each data frame from which time period of a single bit is predicted. One single bit time is exactly the reciprocal of baud rate i.e. the number of bits per unit time. The detected baud rate value is compared with current baud rate setting of the communication module. If any change in baud rate is identified then re-configuration process is executed which is to apply the new baud rate setting to the communication module.

[0036] Some of the advantages of the present invention, are as follows:
• Automatic baud rate detection feature in Modbus RTU slave device used for remote access to a circuit breaker.
• Parallel processing of the received signal through UART engine to decode the data as well through an input port for timing analysis is achieved. This allows the process to keep track of the baud rate of the received data independently, making the baud rate detection process highly responsive without affecting the data processing with undesired delay.
• The detection process is able to directly detect the baud rate without any matching process like some prior methods. Hence it takes equal processing time for any baud rate setting providing consistency in the process.

[0037] Although a method for automatic baud rate detection and a communication module thereof have been described in language specific to structural features and/or methods, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations of the method for automatic baud rate detection and a communication module thereof.