#include <SimpleModbusSlave.h>


#define TOTAL_REGS_SIZE 50
unsigned int holdingRegs[TOTAL_REGS_SIZE]; // function 3 and 16 register array
////////////////////////////////////////////////////////////

void setup()
{
  randomSeed(analogRead(0));
  /*
   * arguments are:
   * baude rate
   * slave id
   * tx enable pin (not relevant on arduino)
   * max number of registers
   * low latency
   */
  modbus_configure(38400, 1, 2, TOTAL_REGS_SIZE, 0);
}

void loop()
{
  for (byte i = 0; i < TOTAL_REGS_SIZE; i++)
  {
    holdingRegs[i] = (i%2 ? 1 : 0);
  }

  modbus_update(holdingRegs);

}