[carving master learning programming] Arduino hands-on (59) - RS232 to TTL serial port module

Hello everyone , I meet you again , I'm your friend, Quan Jun .

37 It's about sensors and actuators , It's widely spread on the Internet , Actually Arduino Compatible sensor modules are definitely more than that 37 Species . In view of the fact that I have accumulated some sensor and actuator modules on hand , According to practice come true knowledge （ Do it ） Idea , For the purpose of learning and communication , Here we are going to try a series of experiments one by one , No matter how successful （ Program walk through ） Whether or not , It will be recorded — Small progress or problems that can't be solved , Hope to be able to lead the way .

【Arduino】168 A series of sensor module experiments （ Information + Code + graphics + Simulation ）

Experiment 59 ： RS232 turn TTL2 Generation serial port module brush board module （MAX3232 chip ）

MAX3232 chip

The output stage of proprietary low dropout transmitter is adopted , Using double charge pump in 3.0V to 5.5V The power supply can realize real RS-232 performance , The device only needs four 0.1uF External small size charge pump capacitor .max3232 Make sure that the 120kbps Data rate , Keep at the same time RS-232 Output level .max3232 With two-way receiver and two-way driver , Provide 1uA Off mode , Effectively reduce the efficiency and delay the battery life of portable products . In off mode , The receiver remains active , Monitor external equipment , Consume only 1uA Power supply current ,max3232 The pin of 、 The package and function are respectively consistent with the industrial standard MAX242 and MAX232 compatible . Even when working at high data rates ,max3232 Can still maintain RS-232 The positive and negative requirements of the standard 5.0V Minimum transmitter output voltage .

MAX3232 yes MAXIM A product produced by the company 232 Communication chip , He can turn the level of the logic signal of the single chip microcomputer into RS232 The level of . because RS232 Yes, it is , Positive and negative levels 0 and 1 The signal of , therefore MAX3232 To generate the corresponding positive and negative voltage . In the use of MAX3232 when , First, confirm the voltage supplied by the system , Because this chip , For different working voltages , Different capacitors should be used to generate voltage . After power on , Check it out first 2 Does the foot have +5.4V Above voltage ,6 Feet have -5.4V Above voltage ,16 Whether the pin has voltage , If not, check the corresponding capacitance . Pay attention to 16 Feet must have capacitance , Otherwise, the corresponding voltage may not be generated .

RS232 turn TTL2 Generation serial port module brush board module （MAX3232 chip ）

DB9 Pin function

1 、DCD（ Data Carrier Detect） : Carrier detection . It is mainly used for Modem Notify the computer that it is online , namely Modem Dial tone detected , On line .

2 、RXD（Receive(rx) Data）: This pin is used to receive data sent by external devices ; In your use Modem when , You'll find that RXD The indicator light is flashing , explain RXD There is data entry on the pin （ Computer 2 Pick up MAX232 Of RS232 End TOUT（ Such as PIN7)).

3 、TXD（Transmit(tx) Data）: This pin sends the data of the computer to the external device ; In your use Modem when , You'll find that TXD The indicator light is flashing , Indicates that the computer is passing TXD Pin sends data .

4 、DTR（ Data Terminal Ready ）: Data terminal ready ; When this pin is high , notice Modem Data transmission is possible , The computer is ready .

5 、GND（Ground）: Logically .

6 、DSR（data set ready）: Data set ready ; This pin is high , Notify the computer Modem You are ready to , Data communication is available .

7 、RTS（Request To Send）: Request to send ; This foot is controlled by a computer , To inform Modem Send data to the computer immediately ; otherwise ,Modem Temporarily put the received data into the buffer .

8 、CTS（Clear to send）: Clear send ; This foot is made by Modem control , It is used to inform the computer to send the data to Modem.

9 、RI （ Ring Indicator）: Modem Notify the computer of a call coming in , Whether to answer the call is decided by the computer .

To realize the communication between serial ports , At least three pins are required , namely ：RXD,TXD,GND,RXD With other serial ports TXD Connected to a ,TXD And RXD Connected to a ,GND And GND Connected to a , This realizes the communication between serial ports . The communication is full duplex , That is, it can be sent at the same time / receive data , Although it is serial , But because of sending / Reception is not a channel used , Therefore, full duplex can be realized .

DB9 And MAX3232 Connection circuit diagram of

Electrical schematic diagram of the module

Experiment with open source code

/* 【Arduino】168 A series of sensor module experiments （59）  Experiment 59 ： RS232 turn TTL2 Generation serial port module brush board module （MAX3232 chip ）  One of the procedures , Read the serial port data in the cache   Pay attention to the wiring method here , Soft serial port RX Pick up RS232 Of adapter plate RX mouth , TX Pick up RS232 Of adapter plate TX mouth  */

 

#include <SoftwareSerial.h>

SoftwareSerial DLSerial(6, 7); //  Soft serial port  RX(D6), TX(D7)

void setup() { 
   

DLSerial.begin(9600); // Device baud rate 9600

}

 

void loop() { 
       

DLSerial.write(1); // Send byte data 

DLSerial.write(3);

delay(500);

while (DLSerial.available()>0) // If there is received data in the cache 

{ 
   

    DLSerial.read(); // Read the serial port data in the cache 

    delay(2);

}

delay(500);

}

Copy

/* 【Arduino】168 A series of sensor module experiments （59）  Experiment 59 ： RS232 turn TTL2 Generation serial port module brush board （MAX3232 chip ）  Procedure II , Receive serial data  rx = 6 tx = 7 */

 

#include <ctype.h>

 

#define bit9600Delay 100 

#define halfBit9600Delay 50

#define bit4800Delay 188 

#define halfBit4800Delay 94 

 

byte rx = 6;

byte tx = 7;

byte SWval;

 

void setup() { 
   

  pinMode(rx,INPUT);

  pinMode(tx,OUTPUT);

  digitalWrite(tx,HIGH);

  delay(2);

  digitalWrite(13,HIGH); 

  SWprint('o');  

  SWprint('k');

  SWprint(10);

}

 

void SWprint(int data)

{ 
   

  byte mask;

 

  digitalWrite(tx,LOW);

  delayMicroseconds(bit9600Delay);

  for (mask = 0x01; mask>0; mask <<= 1) { 
   

    if (data & mask){ 
    

     digitalWrite(tx,HIGH); 

    }

    else{ 
   

     digitalWrite(tx,LOW); 

    }

    delayMicroseconds(bit9600Delay);

  }

  

  digitalWrite(tx, HIGH);

  delayMicroseconds(bit9600Delay);

}

 

int SWread()

{ 
   

  byte val = 0;

  while (digitalRead(rx));

 

  if (digitalRead(rx) == LOW) { 
   

    delayMicroseconds(halfBit9600Delay);

    for (int offset = 0; offset < 8; offset++) { 
   

     delayMicroseconds(bit9600Delay);

     val |= digitalRead(rx) << offset;

    }

    

    delayMicroseconds(bit9600Delay); 

    delayMicroseconds(bit9600Delay);

    return val;

  }

}

 

void loop()

{ 
   

    SWval = SWread(); 

    SWprint(toupper(SWval));

}

Copy

Experimental simulation programming （linkboy）

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