// modbus slave simple demo model  RGK 2023
// version for arduino nano board
/* SimpleModbusSlaveV10 supports function 3, 6 & 16.
   The modbus_update() method updates the holdingRegs register array and checks
   communication.
*/

#include <SimpleModbusSlave.h>

#define SLAVE_ID  1   // modbus slave address
#define TX_RX     2   // RS485 Rx/Tx changeover
#define potmeter  A0  // analog input for sensor demo

#define RY1 10        // relays <> digital pins
#define RY2 9
#define RY3 8
#define RY4 7
#define RY5 6
#define RY6 5
#define RY7 4
#define RY8 3

unsigned char RELAYS = 0;
unsigned char RELAYS_OLD=0;

// Using the enum instruction allows for an easy method for adding and 
// removing registers. Doing it this way saves you #defining the size 
// of your slaves register array each time you want to add more registers
// and at a glimpse informs you of your slaves register layout.

//////////////// registers of your slave ///////////////////
enum 
{     
  // just add or remove registers and your good to go...
  // The first register starts at address 0
  REG_1,
  REG_2,        
  HOLDING_REGS_SIZE // leave this one
  // total number of registers for function 3 and 16 share the same register array
  // i.e. the same address space
};

unsigned int holdingRegs[HOLDING_REGS_SIZE]; // function 3 and 16 register array

void setup()
{
  modbus_configure(&Serial, 9600, SERIAL_8N2, SLAVE_ID, TX_RX, HOLDING_REGS_SIZE, holdingRegs);

  
  DDRB=0b00001111;  //alternatieve pinMode instructie
  DDRD=0b11111100;
}

void loop()
{
  static unsigned int error;
  static unsigned int data;    
  modbus_update();
  RELAYS = lowByte(holdingRegs[REG_1]);// get content of Modbus register 1 and use lower byte for relays
  if(RELAYS!=RELAYS_OLD)//only if something is changed
  {
    digitalWrite(RY1,(bitRead(RELAYS,0)));
    digitalWrite(RY2,(bitRead(RELAYS,1)));
    digitalWrite(RY3,(bitRead(RELAYS,2)));
    digitalWrite(RY4,(bitRead(RELAYS,3)));
    digitalWrite(RY5,(bitRead(RELAYS,4)));
    digitalWrite(RY6,(bitRead(RELAYS,5)));
    digitalWrite(RY7,(bitRead(RELAYS,6)));
    digitalWrite(RY8,(bitRead(RELAYS,7)));                  
    RELAYS_OLD=RELAYS;
  }
  
  data= analogRead(potmeter); //read analog input (potmeter voltage)
  holdingRegs[REG_2] = data;// put analog value in Modbus register 2      
}