- What Is A Serial Connection
- Bluetooth Serial Connection Matlab Functions In Word
- Send Data From Matlab To Arduino Via Bluetooth
Serial communication is the most common low-level protocol for communicating between two ormore devices. Normally, one device is a computer, while the other device can be a modem, aprinter, Arduino ® hardware, another computer, or a scientific instrument such as an oscilloscopeor a function generator. For many serial port applications, you can communicate with yourinstrument without detailed knowledge of how the serial port works. Communication through aserial port is established with a serialport object, which you create inthe MATLAB ® workspace.
For information about creating a serialportobject, see.Before you can write or read data, the serialport object and the instrumentmust have identical communication settings. For information, see. Basic features of serial port communication.Establish a connection between MATLAB and the device using the serial port.Set properties associated with the device baud rate and serial data format.Write and read both text and binary data with a serial port device.Enhance instrument communication by executing a callback function when a specifiedevent occurs on the device.Signal the presence of connected devices and control the flow of data usingcontrol pins.Connect to serial port devices using serialport instead of serial.
Overview of the Serial Port IntroductionFor many serial port applications, you can communicate with your device withoutdetailed knowledge of how the serial port works. If your application isstraightforward, or if you are already familiar with the previously mentionedtopics, you might want to begin with to see how to use your serial port device withMATLAB ® software. What Is Serial Communication?Serial communication is the most common low-level protocol for communicatingbetween two or more devices. Normally, one device is a computer, while the otherdevice can be a modem, a printer, another computer, or a scientific instrument suchas an oscilloscope or a function generator.As the name suggests, the serial port sends and receives bytes of information in aserial fashion — one bit at a time.
These bytes are transmitted using eithera binary (numerical) format or a text format. The Serial Port Interface StandardThe serial port interface for connecting two devices is specified by theTIA/EIA-232C standard published by the Telecommunications IndustryAssociation.The original serial port interface standard was given by RS-232, which stands forRecommended Standard number 232. The term RS-232 is still inpopular use, and is used in this guide when referring to a serial communication portthat follows the TIA/EIA-232 standard. RS-232 defines these serial portcharacteristics.The maximum bit transfer rate and cable length.The names, electrical characteristics, and functions of signals.The mechanical connections and pin assignmentsPrimary communication is accomplished using three pins: the Transmit Data pin, theReceive Data pin, and the Ground pin.
Other pins are available for data flowcontrol, but are not required.Other standards such as RS-485 define additional functionality such as higher bittransfer rates, longer cable lengths, and connections to as many as 256devices. Connecting Two Devices with a Serial CableThe RS-232 standard defines the two devices connected with a serial cable as theData Terminal Equipment (DTE) and Data Circuit-Terminating Equipment (DCE). Thisterminology reflects the RS-232 origin as a standard for communication between acomputer terminal and a modem.Throughout this guide, your computer is considered a DTE, while peripheral devicessuch as modems and printers are considered DCEs. Many scientific instrumentsfunction as DTEs.Because RS-232 mainly involves connecting a DTE to a DCE, the pin assignments aredefined such that straight-through cabling is used, where pin 1 is connected to pin1, pin 2 is connected to pin 2, and so on.
The following diagram shows a DTE to DCEserial connection using the transmit data (TD) pin and the receive data (RD)pin.For more information about serial port pins, see. NoteYou can connect multiple RS-422 or RS-485 devices to a serial port.
If youhave an RS-232/RS-485 adaptor, you can use the MATLAB serial port object with these devices. Serial Port Signals and Pin AssignmentsSerial ports consist of two signal types: data signals and control signals.
Tosupport these signal types, as well as the signal ground, the RS-232 standarddefines a 25-pin connection. However, most Windows ® and UNIX ® platforms use a 9-pin connection. In fact, only three pins arerequired for serial port communications: one for receiving data, one fortransmitting data, and one for the signal ground.The following diagram shows the pin assignment scheme for a 9-pin male connectoron a DTE. NoteThe serial port pin and signal assignments are with respect to the DTE. Forexample, data is transmitted from the TD pin of the DTE to the RD pin of theDCE. Signal StatesSignals can be in either an active state or aninactive state. An active state corresponds to thebinary value 1, while an inactive state corresponds to the binary value 0.
Anactive signal state is often described as logic 1,on, true, or amark. An inactive signal state is often described aslogic 0, off,false, or a space.For data signals, the on state occurs when the receivedsignal voltage is more negative than -3 volts, while the offstate occurs for voltages more positive than 3 volts. For control signals, theon state occurs when the received signal voltage is morepositive than 3 volts, while the off state occurs forvoltages more negative than -3 volts. The voltage between -3 volts and +3 voltsis considered a transition region, and the signal state is undefined.To bring the signal to the on state, the controlling deviceunasserts (or lowers) thevalue for data pins and asserts (orraises) the value for control pins. Conversely, tobring the signal to the off state, the controlling deviceasserts the value for data pins and unasserts the value for control pins.The following diagram shows the on andoff states for a data signal and for a controlsignal. The Data PinsMost serial port devices support full-duplexcommunication meaning that they can send and receive data at the same time.Therefore, separate pins are used for transmitting and receiving data. For thesedevices, the TD, RD, and GND pins are used.
However, some types of serial portdevices support only one-way or half-duplexcommunications. For these devices, only the TD and GND pins are used.
This guideassumes that a full-duplex serial port is connected to your device.The TD pin carries data transmitted by a DTE to a DCE. The RD pin carries datathat is received by a DTE from a DCE. The Control PinsThe control pins of a 9-pin serial port are used to determine the presence ofconnected devices and control the flow of data.
The control pins include.The RTS and CTS Pins. The RTS and CTS pins are used to signal whether the devices are ready tosend or receive data. This type of data flow control—calledhardware handshaking—is used to preventdata loss during transmission. When enabled for both the DTE and DCE,hardware handshaking using RTS and CTS follows these steps.The DTE asserts the RTS pin to instruct the DCEthat it is ready to receive data.The DCE asserts the CTS pin indicating that it isclear to send data over the TD pin. If data can no longer be sent,the CTS pin is unasserted.The data is transmitted to the DTE over the TDpin.
If data can no longer be accepted, the RTS pin is unasserted bythe DTE and the data transmission is stopped.To enable hardware handshaking in MATLAB software, see.The DTR and DSR Pins. Many devices use the DSR and DTR pins to signal if they are connected andpowered.
Signaling the presence of connected devices using DTR and DSRfollows these steps.The DTE asserts the DTR pin to request that theDCE connect to the communication line.The DCE asserts the DSR pin to indicate it isconnected.DCE unasserts the DSR pin when it is disconnectedfrom the communication line.DTR/DSR lines have multiple purposes depending on the application. Forexample these lines can be used for handshaking, flow control, or evenproviding power to the unit. However RTS/CTS lines are mostly used for dataflow control between the host and device. Refer to your device documentationto determine its specific pin behavior.The CD and RI Pins. The CD and RI pins are typically used to indicate the presence of certainsignals during modem-modem connections.A modem uses a CD pin to signal that it has made a connection withanother modem, or has detected a carrier tone. CD is asserted when the DCEis receiving a signal of a suitable frequency.
CD is unasserted if the DCEis not receiving a suitable signal.The RI pin is used to indicate the presence of an audible ringing signal.RI is asserted when the DCE is receiving a ringing signal. RI is unassertedwhen the DCE is not receiving a ringing signal (e.g., it is betweenrings). Serial Data FormatThe serial data format includes one start bit, between five and eight data bits,and one stop bit.
A parity bit and an additional stop bit might be included in theformat as well. The following diagram illustrates the serial data format. Number of data bits - parity type - number of stop bitsFor example, 8-N-1 is interpreted as eight data bits, no parity bit, and one stopbit, while 7-E-2 is interpreted as seven data bits, even parity, and two stopbits.The data bits are often referred to as a character becausethese bits usually represent an ASCII character. The remaining bits are calledframing bits because they frame the data bits. Bytes Versus ValuesA byte is the collection of bits that comprise theserial data format. At first, this term might seem inaccurate because a byte is8 bits and the serial data format can range between 7 bits and 12 bits.
However,when serial data is stored on your computer, the framing bits are stripped away,and only the data bits are retained. Moreover, eight data bits are always usedregardless of the number of data bits specified for transmission, with theunused bits assigned a value of 0.When reading or writing data, you might need to specify avalue, which can consist of one or more bytes.
Forexample, if you read one value from a device using the int32format, that value consists of four bytes. For more information about readingand writing values, see.
Synchronous and Asynchronous CommunicationThe RS-232 standard supports two types of communication protocols: synchronousand asynchronous.Using the synchronous protocol, all transmitted bits are synchronized to acommon clock signal. The two devices initially synchronize themselves to eachother, and continually send characters to stay synchronized. Even when actualdata is not really being sent, a constant flow of bits allows each device toknow where the other is at any given time. That is, each bit that is sent iseither actual data or an idle character. Synchronous communications allowsfaster data transfer rates than asynchronous methods, because additional bits tomark the beginning and end of each data byte are not required.Using the asynchronous protocol, each device uses its own internal clock,resulting in bytes that are transferred at arbitrary times.
So, instead of usingtime as a way to synchronize the bits, the data format is used.In particular, the data transmission is synchronized using the start bit ofthe word, while one or more stop bits indicate the end of the word. Therequirement to send these additional bits causes asynchronous communications tobe slightly slower than synchronous. However, it has the advantage that theprocessor does not have to deal with the additional idle characters. Most serialports operate asynchronously.The start bit is transmitted with a value of 0.The data bits are transmitted. The first data bitcorresponds to the least significant bit (LSB), while the last data bitcorresponds to the most significant bit (MSB).The parity bit (if defined) is transmitted.One or two stop bits are transmitted, each with avalue of 1.The baud rate is the number of bits transferred persecond.
The transferred bits include the start bit, the data bits, the paritybit (if defined), and the stop bits. Start and Stop BitsAs described in,most serial ports operate asynchronously. This means that the transmitted bytemust be identified by start and stop bits. The start bit indicates when the databyte is about to begin; the stop bit(s) indicate(s) when the data byte has beentransferred. The process of identifying bytes with the serial data formatfollows these steps.When a serial port pin is idle (not transmittingdata), it is in an on state.When data is about to be transmitted, the serial portpin switches to an off state due to the startbit.The serial port pin switches back to anon state due to the stop bit(s).
This indicatesthe end of the byte.Data BitsThe data bits transferred through a serial port might represent devicecommands, sensor readings, error messages, and so on. The data can betransferred as either binary data or ASCII data.Most serial ports use between five and eight data bits.
What Is A Serial Connection
Binary data istypically transmitted as eight bits. Text-based data is transmitted as eitherseven bits or eight bits.
If the data is based on the ASCII character set, aminimum of seven bits is required because there are2 7 or 128 distinct characters. If an eighth bitis used, it must have a value of 0. If the data is based on the extended ASCIIcharacter set, eight bits must be used because there are2 8 or 256 distinct characters. The Parity BitThe parity bit provides simple error (parity) checking for the transmitteddata. The following table shows the types of parity checking.
NoteParity checking can detect only 1-bit errors. Multiple-bit errors canappear as valid data.For example, suppose the data bits 01110001 are transmitted to your computer.If even parity is selected, the parity bit is set to 0 by the transmittingdevice to produce an even number of 1s.
If odd parity is selected, the paritybit is set to 1 by the transmitting device to produce an odd number of1s. Finding Serial Port Information for Your PlatformThis section describes the ways to find serial port information for Windows and UNIX platforms. NoteYour operating system provides default values for all serial port settings.However, these settings are overridden by your MATLAB code, and will have no effect on your serial portapplication.
Use the seriallist FunctionThe seriallist function returns a list of all serial portson a system. The list includes virtual serial ports provided by USB-to-serialdevices and Bluetooth Serial Port Profile devices.
This provides a list of theserial ports that you have access to on your computer and could use for serialport communication. Stty speed 4800 /dev/ttyS0 Using Virtual USB Serial PortsIf you have devices that present themselves as serial ports on your operatingsystem, you can use them as virtual USB serial ports in MATLAB.
Bluetooth Serial Connection Matlab Functions In Word
An example of such devices would be a USB Serial Dongle. ForBluetooth ® devices, use the Bluetooth support in the InstrumentControl Toolbox™.
Send Data From Matlab To Arduino Via Bluetooth
See (Instrument Control Toolbox) formore information.MATLAB can communicate with these devices as long as the serial driversprovided by the device vendor are able to emulate the native hardware. Certainsoftware, like HyperTerminal, does not require the device driver to fully implementand support the native hardware. Selected Bibliography.