MAX232 is used to interface the microcontroller to standard RS-232 port of personal computer. It is a signal level converter necessary for conversion between TTL and RS-232 standards.
The MAX232 requires 5 external 10uF capacitors. These are used by the internal charge pump to create +10 volts and -10 volts. The MAX232 includes 2 receivers and 2 transmitters so two serial ports can be used with a single chip. We will only use one transmitter for this project. The only connection that must be made to the 8052 is one jumper from pin 3 of the 8052 to pin 11 of the MAX232.
The circuit diagram shown below illustrates the connection of RS232 with microcontroller and serial port DB9 connector.Data is transmitted and received on pins 2 and 3 respectively. Data Set Ready (DSR) is an indication from the Data Set (i.e., the modem or DSU/CSU) that it is on. Similarly, DTR indicates to the Data Set that the DTE is on. Data Carrier Detect (DCD) indicates that a good carrier is being received from the remote modem.
Pins 4 RTS (Request To Send - from the transmitting computer) and 5 CTS (Clear To Send - from the Data set) are used to control. In most Asynchronous situations, RTS and CTS are constantly on throughout the communication session. However where the DTE is connected to a multipoint line, RTS is used to turn carrier on the modem on and off. On a multipoint line, it's imperative that only one station is transmitting at a time (because they share the return phone pair). When a station wants to transmit, it raises RTS. The modem turns on carrier, typically waits a few milliseconds for carrier to stabilize, and then raises CTS. The DTE transmits when it sees CTS up. When the station has finished its transmission, it drops RTS and the modem drops CTS and carrier together.
Clock signals (pins 15, 17, & 24) are only used for synchronous communications. The modem or DSU extracts the clock from the data stream and provides a steady clock signal to the DTE. Note that the transmit and receive clock signals do not have to be the same, or even at the same baud rate.
Note: Transmit and receive leads (2 or 3) can be reversed depending on the use of the equipment - DCE Data Communications Equipment or a DTE Data Terminal Equipment.
CTS Clear To Send
DCD Data Carrier Detected (Tone from a modem)
DCE Data Communications Equipment eg. modem
DSR Data Set Ready
DSRS Data Signal Rate Selector (Not commonly used)
DTE Data Terminal Equipment eg. computer, printer
DTR Data Terminal Ready
FG Frame Ground (screen or chassis)
NC No Connection
RCk Receiver (external) Clock input
RI Ring Indicator (ringing tone detected)
RTS Request To Send
RxD Received Data
SG Signal Ground
SCTS Secondary Clear To Send
SDCD Secondary Data Carrier Detected (Tone from a modem)
SRTS Secondary Request To Send
SRxD Secondary Received Data
STxD Secondary Transmitted Data
TxD Transmitted Data
The RS232 connector was originally developed to use 25 pins. In this DB25 connector pinout provisions were made for a secondary serial RS232 communication channel.
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The MAX232 requires 5 external 10uF capacitors. These are used by the internal charge pump to create +10 volts and -10 volts. The MAX232 includes 2 receivers and 2 transmitters so two serial ports can be used with a single chip. We will only use one transmitter for this project. The only connection that must be made to the 8052 is one jumper from pin 3 of the 8052 to pin 11 of the MAX232.
The circuit diagram shown below illustrates the connection of RS232 with microcontroller and serial port DB9 connector.Data is transmitted and received on pins 2 and 3 respectively. Data Set Ready (DSR) is an indication from the Data Set (i.e., the modem or DSU/CSU) that it is on. Similarly, DTR indicates to the Data Set that the DTE is on. Data Carrier Detect (DCD) indicates that a good carrier is being received from the remote modem.
Pins 4 RTS (Request To Send - from the transmitting computer) and 5 CTS (Clear To Send - from the Data set) are used to control. In most Asynchronous situations, RTS and CTS are constantly on throughout the communication session. However where the DTE is connected to a multipoint line, RTS is used to turn carrier on the modem on and off. On a multipoint line, it's imperative that only one station is transmitting at a time (because they share the return phone pair). When a station wants to transmit, it raises RTS. The modem turns on carrier, typically waits a few milliseconds for carrier to stabilize, and then raises CTS. The DTE transmits when it sees CTS up. When the station has finished its transmission, it drops RTS and the modem drops CTS and carrier together.
Clock signals (pins 15, 17, & 24) are only used for synchronous communications. The modem or DSU extracts the clock from the data stream and provides a steady clock signal to the DTE. Note that the transmit and receive clock signals do not have to be the same, or even at the same baud rate.
Note: Transmit and receive leads (2 or 3) can be reversed depending on the use of the equipment - DCE Data Communications Equipment or a DTE Data Terminal Equipment.
CTS Clear To Send
DCD Data Carrier Detected (Tone from a modem)
DCE Data Communications Equipment eg. modem
DSR Data Set Ready
DSRS Data Signal Rate Selector (Not commonly used)
DTE Data Terminal Equipment eg. computer, printer
DTR Data Terminal Ready
FG Frame Ground (screen or chassis)
NC No Connection
RCk Receiver (external) Clock input
RI Ring Indicator (ringing tone detected)
RTS Request To Send
RxD Received Data
SG Signal Ground
SCTS Secondary Clear To Send
SDCD Secondary Data Carrier Detected (Tone from a modem)
SRTS Secondary Request To Send
SRxD Secondary Received Data
STxD Secondary Transmitted Data
TxD Transmitted Data
The RS232 connector was originally developed to use 25 pins. In this DB25 connector pinout provisions were made for a secondary serial RS232 communication channel.
MAX 232 Interfacing with Microcontroller 8052, PIN configuration of MAX232, microcontroller 8052 and serial communication, Microcontroller51, circuit diagram of serial communication via rs232,Serial Port Pinout, USB communication,messages through RS232 Cable, wiring the RS232 9 Pin, how to interface RS232 and Data Interfaces with microcontroller,RS232 serial connector pin assignment ,RS232 DB9 to DB25 converter ,RS232 serial loopback test plugs ,RS232 null modem cables , monitor cable ,Serial printer cables ,Yost RS232 on RJ45 standard RS232 support,USB to RS232 converter,Use tan delta measurement to confirm reliability of your cables,Connect USB Printer to PC Parallel Port with LPT2USB Adapter,Virtual port COM, Ethernet 10/100 Rail DIN, Isolated, Industrial Use,how to use the ic RS232, converters from RS232 to RS485, formation of RS 232 Cable, connector RS232 a RJ45,rs-232 pinout,circuit diagram of rs-232c,connector rj-45,serial communication based on rs-485,RS-232 is a standard for communication between devices, such as a modem and computer.Interfacing The Serial / RS-232 PortDetailed explanations on interfacing the serial port.RS232: RS232 Connector wiring RS232 configuration - diagrams of PC connectors for conection of RS232 devices, with and without handshaking. RS232 Specifications and standardPractical discussion of the RS232 standard and its specifications RS232 serial cable pinout information RS232 serial cables and adapters. Pinout and wiring layout for many situations. DB9 to DB25 conversion and null modem wiring diagrams. microcontroller to pc interaction using vb gui application control projects with micro voltmeter using 89c51 with lcd display with circuit diagrams
"Help on micro controller 8051 project"
ReplyDeletehi sir
we are doing project on "automatic load shedding using gsm" , our idea is to control two or more relay through SMS .
sms format is "" status means ON/OFF.
In this project we are controlling ‘2’ number of relays (According to the availability of ports in the MC) that are connected directly to the power lines. And these relays are driven by a micro controller unit. In this micro controller unit we are employing one timer/RTC (real time clock) for the desired delay (Line off time), say suppose it is 30 min., we have to turn off line 1. for 30 min and after 30 min. again we have to turn it ON and turn OFF line 2. for 30 min and so on. We should program the micro controller according to above-mentioned idea. And one more thing is, the user should be able to adjust the delay. That is, the system should accept some inputs given by the user. That is, we are employing one GSM mobile and an LCD to enter the desired delay and once the delay is entered then the system will work with that delay till the next change given by the user..
PLEASE HELP US SIR AND SEND THE CODE FOR THE ABOVE IDEA .
WE ARE USING FOLLOWING HARDWARE
Micro Controller(P89c51RD2)
RTC chip (DS1307)
Relays
GSM Module
PLEASE REPLY SIR SEND US CODE FOR ABOVE IDEA
ITS HUMBLE REQUEST
Help on micro controller 8051 project"
ReplyDeletehi sir
we are doing project on "automatic load shedding using gsm" , our idea is to control two or more relay through SMS .
sms format is "" status means ON/OFF.
when we switch on the micro controller and gsm we should get acknowledgment message to the owner and according to the message relay should operate ,
when the time of operation is complete automatically the next relay should operate. The sent message and time should display on lcd.
PLEASE HELP US SIR AND SEND THE CODE FOR THE ABOVE IDEA .
WE ARE USING FOLLOWING HARDWARE
1. P89C51RD2 MICRO CONTROLLER
2. 16X2 LCD DISPLAY
3. RTC OR TIMER
4. GSM MODULE
5. RELAYS
PLEASE REPLY SIR SEND US CODE FOR ABOVE IDEA
ITS HUMBLE REQUEST
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ReplyDeleteds1685 graphic displays programming with microcontrollers beginners microcontroller communication 8051 project on furnace
please sir, tell me the functions of all capacitors connected to the max232
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