// To include the SimpleModbusSlave.h download ZIP https://github.com/jecrespo/simple-modbus/tree/master and extract it. Search for folder Simple Modbus. Then, create a ZIP file from the Simple Modbus folder and install it. 
#include <SimpleModbusSlave.h>
#include <OneWireSTM.h>
#include <DallasTemperature.h>

#define ONE_WIRE_BUS PA15       // DS18B20 One-Wire pin
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

// RS485 control pins
#define RS485_DE_PIN PB5   // DE (Driver Enable) pin
#define RS485_RE_PIN PA15  // RE (Receiver Enable) pin

// Define Modbus parameters
#define SLAVE_ID 1
#define HOLDING_REGS_SIZE 2

// Modbus holding registers
unsigned int holdingRegs[HOLDING_REGS_SIZE];

void setup() {
  afio_cfg_debug_ports(AFIO_DEBUG_SW_ONLY); 
  // Initialize Serial2 for RS485 communication.
  Serial2.begin(9600);
  
 

  // Configure Modbus with correct parameters
  modbus_configure(9600, SLAVE_ID, RS485_DE_PIN, HOLDING_REGS_SIZE, 0);  // 0 for low latency

  // Debug output
  Serial.begin(9600);
  Serial.println("Modbus Slave Setup Complete");
}

void loop() {
  // Initialize OneWire for DS18B20 temperature sensor. Initialized inside the loop () due to the pins conflict of R485, sensor board.
  sensors.begin();
  // Update Modbus register values
  modbus_update(holdingRegs);  // Pass holding registers

  // Read temperature from DS18B20 sensor
  sensors.requestTemperatures();
  float temperatureC = sensors.getTempCByIndex(0);  // Get temperature in Celsius

  // Store the temperature in Modbus holding register (scaled by 100)
  holdingRegs[0] = (unsigned int)(temperatureC * 100);
  // Set RS485 DE/RE control pins as output
  pinMode(RS485_DE_PIN, OUTPUT);
  pinMode(RS485_RE_PIN, OUTPUT);
  digitalWrite(RS485_DE_PIN, LOW);   // Set DE to LOW (receive mode)
  digitalWrite(RS485_RE_PIN, LOW);   // Set RE to LOW (receive mode)
  // Print temperature to Serial for debugging
  Serial.print("Temperature: ");
  Serial.print(temperatureC);
  Serial.println(" °C");

  delay(1000);  // Delay between temperature reads
}