add_modbus_signal

This function registers a Modbus I/O signal in advance so that it can be used. A Modbus I/O signal registered with this function is stored in memory, so it must be set up again after a reboot. However, a signal registered in the T/P application can be reused, because it is added during the initialization process.

Definition
DRFLEx.h within class CDRFLEx, public section

bool add_modbus_signal(string strSymbol,
                       string strIpAddress,
                       unsigned short nPort,
                       MODBUS_REGISTER_TYPE eRegType,
                       unsigned short iRegIndex,
                       unsigned short nRegValue = 0,
                       unsigned char nSlaiveId = 255)
{
    return _add_modbus_signal(_rbtCtrl,
                              strSymbol.c_str(),
                              strIpAddress.c_str(),
                              nPort,
                              eRegType,
                              iRegIndex,
                              nRegValue,
                              nSlaiveId);
};

Parameter

Parameter Name	Data Type	Default Value	Description
strSymbol	string		Modbus signal name
strIpAddress	string		Modbus module IP address
nPort	unsigned short		Modbus module port number
eRegType	MODBUS_REGISTER_TYPE		Modbus register type definitions
iRegIndex	unsigned short		Index of the Modbus register to access
nRegValue	unsigned short	0	Output value when the type is `MODBUS_REGISTER_TYPE_COILS` or `MODBUS_REGISTER_TYPE_HOLDING_REGISTER` (ignored for other types)
nSlaiveId	unsigned char	255	Slave ID of the target Modbus device (default: broadcast)

Return

Value	Description
0	Error — failed to register Modbus signal
1	Success — Modbus signal successfully added

Example

// Example of connecting Modbus I/O and allocating context point
// Modbus IP: 192.168.127.254
// Add 2 points: "di1", "di2"

drfl.add_modbus_signal("di1", "192.168.127.254", 502,
                       MODBUS_REGISTER_TYPE_DISCRETE_INPUTS, 0, 0);
drfl.add_modbus_signal("di2", "192.168.127.254", 502,
                       MODBUS_REGISTER_TYPE_DISCRETE_INPUTS, 0, 0);

This example registers two Modbus digital input points named di1 and di2 on the external Modbus module connected via TCP at IP 192.168.127.254, port 502. Once registered, the signals can be monitored or controlled in subsequent API calls.