[Bug]: Modbus: Reading Coils as an array returns only the first value

[IsmoLeszczynski]

What happened?

When defining a ModbusTag with array size > 1, the ModbusOptimizer.processReadResponses(...) ModbusTagCoil logic returns only the first bit as the result. The array logic works correctly for registers, but the customized coil logic is missing the array handling:

plc4x/plc4j/drivers/modbus/src/main/java/org/apache/plc4x/java/modbus/base/optimizer/ModbusOptimizer.java

Lines 210 to 216 in a7ab2cf

	// Calculate the byte that contains the response for this Coil
	byte[] responseData = response.getResponseData();
	int bitPosition = coilTag.getAddress() - response.startingAddress;
	int bytePosition = bitPosition / 8;
	int bitPositionInByte = bitPosition % 8;
	boolean isBitSet = (responseData[bytePosition] & (1 << bitPositionInByte)) != 0;
	values.put(tagName, new DefaultPlcResponseItem<>(PlcResponseCode.OK, new PlcBOOL(isBitSet)));

What it should do is check for the for the modbusTag.getNumberOfElements() and generate the PlcList when needed. My current development version fixes this as follows:

if (modbusTag.getNumberOfElements() > 1) {
  PlcList bitValues = new PlcList();
  for (int i = 0; i < modbusTag.getNumberOfElements(); i++) {
    int bitPosition = modbusTag.getAddress() - response.startingAddress + i;
    boolean isBitSet = getIsBitSet(bitPosition, responseData);
    bitValues.add(new PlcBOOL(isBitSet));
  }
  values.put(tagName, new DefaultPlcResponseItem<>(PlcResponseCode.OK, bitValues));
} else {
  int bitPosition = modbusTag.getAddress() - response.startingAddress;
  boolean isBitSet = getIsBitSet(bitPosition, responseData);
  values.put(tagName, new DefaultPlcResponseItem<>(PlcResponseCode.OK, new PlcBOOL(isBitSet)));
}

private static boolean getIsBitSet(int bitPosition, byte[] responseData) {
  int bytePosition = bitPosition / 8;
  int bitPositionInByte = bitPosition % 8;
  boolean isBitSet = (responseData[bytePosition] & (1 << bitPositionInByte)) != 0;
  return isBitSet;
}

Version

v0.13.0-SNAPSHOT

Programming Languages

• plc4c
• plc4go
• plc4j
• plc4net
• plc4py

Protocols

• AB-Ethernet
• ADS /AMS
• BACnet/IP
• C-Bus
• CANopen
• EtherNet/IP
• Firmata
• IEC-69870
• KNXnet/IP
• Modbus
• OPC-UA
• Profinet
• S7
• S7-light