关于485的一个问题

#include <M5Stack.h>
#define RX_PIN      16
#define TX_PIN      17

#define X_OFF 160
#define Y_OFF 30

int i=0,s=0;

void setup() {
  M5.begin();
  M5.Power.begin();
  M5.Lcd.setTextSize(1);
  M5.Lcd.drawString("RS485 Unit test", 75, 3, 4);
  Serial.begin(115200);
  Serial2.begin(115200, SERIAL_8N1, RX_PIN, TX_PIN);  //Set the baud rate of serial port 2 to 115200,8 data bits, no parity bits, and 1 stop bit, and set RX to 16 and TX to 17.  设置串口二的波特率为115200,8位数据位,没有校验位,1位停止位,并设置RX为16,TX为17
}


void loop() {
 

  if(Serial2.available()){
    M5.Lcd.print(char(Serial2.read()));
 }
  delay(100);
}

 

 

 

 

 

 可以正常显示出向串口发送的数据；可是使用如下的代码向串口写(不改变接线)，llcom读不到任何内容

#include <M5Stack.h>
#define RX_PIN      16
#define TX_PIN      17

#define X_OFF 160
#define Y_OFF 30

int i=0,s=0;

void setup() {
  M5.begin();
  M5.Power.begin();
  M5.Lcd.setTextSize(1);
  M5.Lcd.drawString("RS485 Unit test", 75, 3, 4);
  Serial.begin(115200);
  Serial2.begin(115200, SERIAL_8N1, RX_PIN, TX_PIN);  //Set the baud rate of serial port 2 to 115200,8 data bits, no parity bits, and 1 stop bit, and set RX to 16 and TX to 17.  设置串口二的波特率为115200,8位数据位,没有校验位,1位停止位,并设置RX为16,TX为17
}


void loop() {
  Serial2.write("Hello\n");

  if(Serial2.available()){
    M5.Lcd.print(char(Serial2.read()));
 }
  delay(100);
}

 

 llcom读不到任何内容，但是依然能显示出来

改成下面这样，llcom依旧读不到

#include <M5Stack.h>
#define RX_PIN      16
#define TX_PIN      17

#define X_OFF 160
#define Y_OFF 30

int i=0,s=0;

void setup() {
  M5.begin();
  M5.Power.begin();
  M5.Lcd.setTextSize(1);
  M5.Lcd.drawString("RS485 Unit test", 75, 3, 4);
  Serial.begin(115200);
  Serial2.begin(115200, SERIAL_8N1, RX_PIN, TX_PIN);  //Set the baud rate of serial port 2 to 115200,8 data bits, no parity bits, and 1 stop bit, and set RX to 16 and TX to 17.  设置串口二的波特率为115200,8位数据位,没有校验位,1位停止位,并设置RX为16,TX为17
}


void loop() {
  Serial2.write("Hello\n");
  delay(100);
}

 

不知道是为什么

 

标签：M5,begin,115200,TX,RX,问题,关于,485,define
来源： https://www.cnblogs.com/ykts/p/15855601.html