Serial.begin(9600);

pinMode(2, OUTPUT); // TTL -> RS485 chip driver pin

}

void loop() {

static ulong timepoint = 0;

if (millis() - timepoint > 1000) {

read_command();

timepoint = millis();

}

if (Serial.available() > 0) data_return();

//

delay(1000);

}

/************************Send command to Analogue_Test and SHT1X Module******

*******************/

void read_command()

{

int i;

char sum_cmd = 0;

digitalWrite(EN, HIGH); // Turn the drvier pin to HIGH -> Turn on code tran

smitting mode for the RS485 interface

// Turn the driver pin to LOW

-> Turn on reading mode for the RS485 interf

ace

delay(10);

cmd[0] = 0x55;

cmd[1] = 0xaa;

cmd[2] = addr;

cmd[3] = 0x00;

cmd[4] = 0x21;

for (i = 0; i < 5; i++) {

sum_cmd += cmd[i];

}