/* Request Cunstruct packet to send
* @param: none
* @return: none
* @private
* @comment: none
*/
void Modbus::constructPacket()
{
//Disable next transmission until get response packet or timeout
_transmission_ready_flag = false;
_packet->requests++;
_total_request++; //calculate total packets are requested
//Modbus Application Protocol v1.13b
frame[0] = _packet->id;
frame[1] = _packet->function;
frame[2] = _packet->address >> 8; //Address Hi
frame[3] = _packet->address & 0xFF; //Address Lo
//If packet is single regiser, data is what it is
if ( _packet->function == PRESET_SINGLE_REGISTER ){
_packet->data = _register_array[_packet->register_start_address];
}
//2 bytes address
frame[4] = _packet->data >> 8; //total registers Hi
frame[5] = _packet->data & 0xFF; //total registers Lo
//Frame size for function code 3, 4 & 6 = 8
uint8_t frameSize;
if (_packet->function == PRESET_MULTIPLE_REGISTERS)
frameSize = construct_F16();
else if (_packet->function == FORCE_MULTIPLE_COILS)
frameSize = construct_F15();
else // else functions 1,2,3,4,5 & 6 is assumed. They all share the exact same request format.
frameSize = 8; // the request is always 8 bytes in size for the above mentioned functions.
//Error check CRC16
uint16_t crc16 = calculateCRC(frameSize - 2); //First 6 bytes of frame is used to calculate CRC error check
frame[frameSize - 2] = crc16 >> 8; //High byte of CRC
frame[frameSize - 1] = crc16 & 0xFF; //Low byte of CRC
#if DEBUG_UART
print("Request: ");
for (uint8_t i=0;i<frameSize;i++)
print(frame[i]);
println();
#endif
//Send packet frame to slave
sendPacket(frameSize);
}
void constructPacket()
{
packet->requests++;
frame[0] = packet->id;
frame[1] = packet->function;
frame[2] = packet->address >> 8; // address Hi
frame[3] = packet->address & 0xFF; // address Lo
// For functions 1 & 2 data is the number of points
// For function 5 data is either ON (0xFF00) or OFF (0x0000)
// For function 6 data is exactly that, one register's data
// For functions 3, 4 & 16 data is the number of registers
// For function 15 data is the number of coils
// The data attribute needs to be intercepted by F5 & F6 because these requests
// include their data in the data register and not in the masters array
if (packet->function == FORCE_SINGLE_COIL || packet->function == PRESET_SINGLE_REGISTER)
packet->data = register_array[packet->local_start_address]; // get the data
frame[4] = packet->data >> 8; // MSB
frame[5] = packet->data & 0xFF; // LSB
unsigned char frameSize;
// construct the frame according to the modbus function
if (packet->function == PRESET_MULTIPLE_REGISTERS)
frameSize = construct_F16();
else if (packet->function == FORCE_MULTIPLE_COILS)
frameSize = construct_F15();
else // else functions 1,2,3,4,5 & 6 is assumed. They all share the exact same request format.
frameSize = 8; // the request is always 8 bytes in size for the above mentioned functions.
unsigned int crc16 = calculateCRC(frameSize - 2);
frame[frameSize - 2] = crc16 >> 8; // split crc into 2 bytes
frame[frameSize - 1] = crc16 & 0xFF;
sendPacket(frameSize);
state = WAITING_FOR_REPLY; // state change
// if broadcast is requested (id == 0) for function 5,6,15 and 16 then override
// the previous state and force a success since the slave wont respond
if (packet->id == 0)
processSuccess();
}
