Constant 0xE4 response

[l3pond]

Hello, @emelianov !

First of all, I must thank you for this great library. I already used this on other personal projects with no sweat.

On this particular one, I'm trying to read data from a energy meter Schneider EasyLogic DM6200 using a TTGO T-Beam V1.0 (ESP32 core). As a transceiver, I'm using HW-726, which converts RS485 to TTL 3.3V.

The settings on the energy meter are:

Protocol: Modbus RTU
Data bits: 8
Baud rate: 9600
Parity: Even
Device Address: 1
Stop Bit: 1

On the other hand, the code that I'm using on the T-Beam side is:

#include <ModbusRTU.h>
#include <HardwareSerial.h>
#include <axp20x.h>

HardwareSerial S(1);

#define RXD 13
#define TXD 2

#define SLAVE_ID 1
#define FIRST_REG 3907
#define REG_COUNT 2

ModbusRTU mb;

// Energy management chip
AXP20X_Class axp;

uint32_t res = 0;

bool cb(Modbus::ResultCode event, uint16_t transactionId, void* data) { // Callback to monitor errors
  if (event != Modbus::EX_SUCCESS) {
    Serial.print("Request result: 0x");
    Serial.println(event, HEX);
  }
  return true;
}

void setup() {
  Serial.begin(115200);

  // AXP192 initializing
  Wire.begin(21, 22);
  if (!axp.begin(Wire, AXP192_SLAVE_ADDRESS)) {
    Serial.println("AXP192 Begin PASS");
  } else {
    Serial.println("AXP192 Begin FAIL");
  }
  axp.setPowerOutPut(AXP192_LDO2, AXP202_ON);   // LoRa
  axp.setPowerOutPut(AXP192_LDO3, AXP202_ON);   // GPS
  axp.setPowerOutPut(AXP192_DCDC2, AXP202_OFF);  // unused
  axp.setPowerOutPut(AXP192_EXTEN, AXP202_OFF);
  axp.setPowerOutPut(AXP192_DCDC1, AXP202_ON);
  axp.setDCDC1Voltage(3300);

  
  S.begin(9600,SERIAL_8E1,RXD,TXD);
  mb.begin(&S);
  mb.master();
  Serial.println("Initializing...");
}

void loop() {
  uint16_t res[REG_COUNT];
  uint32_t current_time = millis();
  static uint32_t prev_time = 0;
  static uint32_t prev_task_time = 0;

  if(current_time - prev_time > 1000){
      prev_time = current_time;
      if (!mb.slave()) {    // Check if no transaction in progress
        mb.readHreg(SLAVE_ID, FIRST_REG, res, REG_COUNT, cb); // Send Read Hreg from Modbus Server
      }
  }
  if (current_time - prev_task_time > 5) { //5ms delay
      prev_task_time = current_time;
      mb.task();
  }
}

The code is an adaptation of #110 solution.

However, I'm getting constant 0xE4 request results, with empty variable.
Any suggestions overcome these constants timeouts? Maybe change the timeout time in MODBUSIP_TIMEOUT 1000 as suggested in #114 ?

Thank you in advance.

[l3pond]

Found the problem. It was on the transducer part.

Thank you!