#include <ModbusMaster.h>
ModbusMaster node;
static uint8_t pzemSlaveAddr = 3;
#define RXD1 32
#define TXD1 25
unsigned cur_time, old_time;

#define MAX485_RE_NEG 33
#define MAX485_DE 33

void preTransmission()
{
  digitalWrite(MAX485_RE_NEG, 1);
  digitalWrite(MAX485_DE, 1);
}

void postTransmission()
{
  digitalWrite(MAX485_RE_NEG, 0);
  digitalWrite(MAX485_DE, 0);
}


void setup() {
  // put your setup code here, to run once:
  digitalWrite(MAX485_RE_NEG, 0);
  digitalWrite(MAX485_DE, 0);
  Serial.begin(115200);
  Serial1.begin(9600, SERIAL_8N1, RXD1, TXD1);
  node.begin(pzemSlaveAddr, Serial1);
  node.preTransmission(preTransmission);
  node.postTransmission(postTransmission);

}

void loop() {
  // put your main code here, to run repeatedly:
  cur_time = millis();
  if (cur_time - old_time >= 3000) {
    uint8_t result;
    uint32_t tempdouble;
    result = node.readHoldingRegisters(171, 2);
    if (result == node.ku8MBSuccess)
    {
      Serial.println("success read modbus1");
    }
    else {
      Serial.println("failed read modbus1");
    }
  }
}