Can't read the Wind Speed & Direction (SEN0483 + SEN0482) data using Arduino and MAX485 (RS485).

Hi there, 

I can't seem to figure out how to read the data from the sensors using standard RS485 protocol with a MAX485 board and the ModbusMaster library. I use an ESP32-S3 Arduino board (using HardwareSerial for UART) and an Arduino UNO R3 (using SoftwareSerial for UART).

This is the MAX485 board I am using: https://www.amazon.ca/dp/B00NIOLNAG?ref=ppx_yo2ov_dt_b_fed_asin_title 

All the wiring is correct, the script is working, but I just don't get any back but some result = 226…

Anyone that could help me out here?

I saw this blog post: https://community.dfrobot.com/makelog-313358.html , but does that mean that it is mandatory to use the Gravity: Active Isolated RS485 to UART Signal Adapter Module (https://www.dfrobot.com/product-2392.html) to make this work?

Thanks!

See code: 
// Include the ModbusMaster library for Modbus RTU communication

#include <ModbusMaster.h>

// Include HardwareSerial library to assign the pins for UART1 and UART2

#include <HardwareSerial.h>

// Define the pins for MAX485 module

// UART1 for Sensor 1

HardwareSerial SerialSensor1(1); // UART1

#define MAX485_DE_RE_1 2 // DE and RE pins are connected together

#define MAX485_RO_RX_1 0 // RO (Receiver Output) pin = RX

#define MAX485_DI_TX_1 1 // DI (Driver Input) pin = TX

// UART2 for Sensor 2

//HardwareSerial SerialSensor2(2); // UART2

//#define MAX485_DE_RE_2 7 // DE and RE pins are connected together

//#define MAX485_RO_RX_2 6 // RO (Receiver Output) pin = RX

//#define MAX485_DI_TX_2 5 // DI (Driver Input) pin = TX

// Create TWO separate ModbusMaster instances

ModbusMaster node1; // For Sensor 1 (UART1/SerialSensor1)

//ModbusMaster node2; // For Sensor 2 (UART2/SerialSensor2)

void setup() {

// Initialize Serial for debugging

Serial.begin(115200);

delay(2000);

Serial.println("Initializing Modbus communication...");

// Initialize Serial1 for RS485 communication

// Initialize UART1 (Sensor 1)

SerialSensor1.begin(9600, SERIAL_8N1, MAX485_DI_TX_1, MAX485_RO_RX_1); // Assign TX and RX pins to UART1

pinMode(MAX485_DE_RE_1, OUTPUT);

digitalWrite(MAX485_DE_RE_1, LOW); // Start in receive mode

// Initialize UART2 (Sensor 2)

//SerialSensor2.begin(9600, SERIAL_8N1, MAX485_DI_TX_2, MAX485_RO_RX_2); // Assign TX and RX pins to UART2

//pinMode(MAX485_DE_RE_2, OUTPUT);

//digitalWrite(MAX485_DE_RE_2, LOW); // Start in receive mode

// Initialize ModbusMaster with the Serial1 port

node1.begin(2, SerialSensor1); // '2' is the Modbus slave ID (0x02 in hex, but library uses decimal)

// Initialize ModbusMaster with the Serial2 port

//node2.begin(2, SerialSensor2); // '2' is the Modbus slave ID (0x02 in hex, but library uses decimal)

Serial.println("Modbus communication initialized. Waiting for data...");

}

void loop() {

float sensorValue = readSensor(node1, MAX485_DE_RE_1, "Wind Speed", "m/s"); // Store returned value

//float windDirection = readSensor(node2, MAX485_DE_RE_2, "Wind Direction", "deg");

delay(1000);

}

float readSensor(ModbusMaster &node, uint8_t de_re_pin, const char* sensorName, const char* sensorUnit) {

// Set MAX485 to transmit mode (assuming DE/RE is controlled elsewhere)

Serial.println(" - Setting DE/RE HIGH...");

digitalWrite(de_re_pin, HIGH);

delay(50);

// Clear response buffer

node.clearResponseBuffer();

// Send Modbus request (Function code 0x03 implied by readHoldRegisters function from ModbusMaster lib, Register adddress 0x0000 = 0x00 0x00, Register length 0x0001 = 0x00 0x01)

Serial.println("Transmitting request...");

uint8_t result = node.readHoldingRegisters(0x0000, 1);

// Set MAX485 to receive mode

Serial.println("Setting DE/RE LOW...");

digitalWrite(de_re_pin, LOW);

if (result == node.ku8MBSuccess) {

uint16_t rawValue = node.getResponseBuffer(0);

float sensorValue = rawValue / 10.0; // Convert to m/s or deg from North 0deg reference. Divided by 10 as per sensor datasheet to get decimal point.

Serial.print(sensorName);

Serial.print(": ");

Serial.print(sensorValue, 1);

Serial.println(sensorUnit);

return sensorValue; // Return the value

} else {

Serial.print(sensorName);

Serial.print(" Error: ");

Serial.println(result); // Prints the raw error code (e.g., 1, 2, 3...)

return -1.0; // Return an error value (e.g., -1)

}

}