#include <modbus.h>

/* Baud rate for UART */
#define BAUD 9600

/* 
 * To match the parameters of HardwareSerial Rx/Tx functions with the Modbus 
 * functions, wrappers around the ::read() and ::write() functions are 
 * required 
*/
MB_StatusTypeDef ArduinoSerial_Tx(void* serial, uint16_t* buf,
				  uint8_t* len, uint8_t* timeout);
MB_StatusTypeDef ArduinoSerial_Rx(void* serial, uint16_t* buf,
				  uint8_t* len, uint8_t* timeout);

MB_StatusTypeDef (*MB_UART_Tx)(void*, uint16_t*, uint8_t*, uint8_t*) =
    &ArduinoSerial_Tx;
MB_StatusTypeDef (*MB_UART_Rx)(void*, uint16_t*, uint8_t*, uint8_t*) =
    &ArduinoSerial_Rx;

/* Single modbus device node */
modbus_slave_device modbus_dev_single;
/* Multiple modbus device nodes.. after all, what is the point of using Modbus 
 * in a single point-to-point connection? */
/* Not illustrated beyond the definition, but should be clear enough */
modbus_slave_device modbus_dev_multiple[10];

uint16_t reg;

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

    /* Set the slave ID to 1 */
    modbus_dev_single.slave_id = 1;
    /* Attach the default HardwareSerial class instance to this node */
    modbus_dev_single.modbus_uart = &Serial;
    
    /* Continuously read this input register in superloop */
    reg = 30001;
}

void loop()
{
    MB_StatusTypeDef status = ReadInputRegisters(&modbus_dev_single, reg, 1);
    if (status == MB_OK) {
	/* Do something with data in the response buffer */
	/* ... */
	ClearResponseBuffer(&modbus_dev_single);
    }    
}

MB_StatusTypeDef ArduinoSerial_Tx(void* serial, uint16_t* buf, uint8_t* len, uint8_t* timeout)
{
    HardwareSerial* _serial = static_cast<HardwareSerial*>(serial);
    if (_serial->availableForWrite()) {
	_serial->write((uint8_t)*buf);
    }
    _serial->flush();
    /* HardwareSerial class funcs do not return any UART errors, sadly */
    return MB_OK;
}

MB_StatusTypeDef ArduinoSerial_Rx(void* serial, uint16_t* buf, uint8_t* len, uint8_t* timeout)
{
    HardwareSerial* _serial = static_cast<HardwareSerial*>(serial);
    buf = _serial->read();
    
    /* HardwareSerial class funcs do not return any UART errors, sadly */
    return MB_OK;
}