This is a very first version of an interface between Arduino and EIB/KNX using the TP-UART interface and Arduino library. The library is based on the KnxTpUart library from https://github.com/thorsten-gehrig/arduino-tpuart-knx-user-forum.

Following are the primary changes:

• Addresses can be given as uint16_t (2byte number) instead of String or 3 separate integers.
• Callback for check if telegram is of interest (when listening for telegrams)
• Support for sending user generated telegram
• Optimize for size (FLASH and RAM)
• Support ATTiny MCUs

Last modified 09.02.2021

For KNX connection the Siemens BCU 5WG1 117-2AB12 is used in any tests.

-> Please note: When using an additional power supply galvanic separation between ARDUINO and BCU is necessary.

The Library is tested on ARDUINO MEGA, ARDUINO UNO and different ATTiny models (ATTiny1614 and ATTiny3216).

-> During programming (if programming through Serial), the BCU should have no connection to the ARDUINO UNO.

The Arduino library is found in the directory KnxTpUart and can be directly placed in Arduino's library folder.

If you have any, don't hesitate to contact me or use the issue tracker. You are also invited to improve the code and send me a pull request to reintegrate the changes here.

To define a KNX connection through standard Serial class use:

KnxTpUart knx(&Serial, KNX_IA(1,1,199));
void setup()
{
    Serial.begin(19200, SERIAL_8E1);
}

To read KNX telegrams from BUS the following must be called frequently:

KnxTpUartSerialEventType eType = knx.serialEvent();

This function should either be called in loop or in serialEvent function (of Arduino).

If eType is KNX_TELEGRAM or IRRELEVANT_KNX_TELEGRAM a KNX telegram is available.

The API provides two different functions, either use groupWrite* or groupAnswer* depending if to send a normal write or an answer (to a previous read). The following examples show both functions, please select the appropriate.

Bool (DPT 1 - 0 or 1)

bool value = true;
knx.groupWriteBool(KNX_GA(1,2,3), value);
knx.groupAnswerBool(KNX_GA(1,2,3), value);

4 Bit Int (DPT 3)

uint8_t value = 7;
knx.groupWrite4BitInt(KNX_GA(1,2,3), value);
knx.groupAnswer4BitInt(KNX_GA(1,2,3), value);

4 Bit Dim (DPT 3)

bool direction = true;
uint8_t steps = 1;
knx.groupWrite4BitDim(KNX_GA(1,2,3), direction, steps);
knx.groupAnswer4BitDim(KNX_GA(1,2,3), direction, steps);

1 Byte int (DTP 5 - 0...255)

int8_t value = -5;
knx.groupWrite1ByteInt(KNX_GA(1,2,3), value);
knx.groupAnswer1ByteInt(KNX_GA(1,2,3), value);

1 Byte unsigned int (DTP 5 - 0...255)

uint8_t value = 255;
knx.groupWrite1ByteInt(KNX_GA(1,2,3), value);
knx.groupAnswer1ByteInt(KNX_GA(1,2,3), value);

2 Byte int (DTP 7 - 0…65 535])

int16_t value = -5;
knx.groupWrite2ByteInt(KNX_GA(1,2,3), value);
knx.groupAnswer2ByteInt(KNX_GA(1,2,3), value);

2 Byte unsigned int (DTP 7 - 0…65 535])

uint16_t value = 0xFFFF;
knx.groupWrite2ByteUInt(KNX_GA(1,2,3), value);
knx.groupAnswer2ByteUInt(KNX_GA(1,2,3), value);

2 Byte Float (DPT9 - -671 088,64 to 670 760,96 )

float value = 250.5;
knx.groupWrite2ByteFloat(KNX_GA(1,2,3), value);
knx.groupAnswer2ByteFloat(KNX_GA(1,2,3), value);

3 Byte Time (DTP 10)

uint8_t weekday = 2;
uint8_t hour    = 10;
uint8_t minute  = 56;
uint8_t second  = 44;
knx.groupWrite3ByteTime(KNX_GA(1,2,3), weekday, hour, minute, second);
knx.groupAnswer3ByteTime(KNX_GA(1,2,3), weekday, hour, minute, second);

3 Byte Date (DTP 11)

uint8_t day   = 2;
uint8_t month = 10;
uint8_t year  = 21;
knx.groupWrite3ByteDate(KNX_GA(1,2,3),day, month, year);
knx.groupAnswer3ByteDate(KNX_GA(1,2,3), day, month, year);

4 byte Float (DTP 14 - -2147483648 to 2147483647)

float value 433.152
knx.groupWrite4ByteFloat(KNX_GA(1,2,3),value);
knx.groupAnswer4ByteFloat(KNX_GA(1,2,3), value);

14 Byte Text (DTP 16)

String value = "Hello World";
knx.groupWrite14ByteText(KNX_GA(1,2,3), value);
knx.groupAnswer14ByteText(KNX_GA(1,2,3), value);

The following code can be used to request a value for a GA:

knx.groupRead(KNX_GA(1,2,3));

The following code shows how to receive a telegram:

KnxTpUartSerialEventType eType = knx.serialEvent();
// A telegram is flagged as IRRELEVANT_KNX_TELEGRAM if it's target is not of interest.
if (eType == KNX_TELEGRAM || eType == IRRELEVANT_KNX_TELEGRAM)
{
    KnxTelegram* telegram = knx.getReceivedTelegram();
}

Bool (DPT 1 - 0 or 1)

bool value = telegram->getBool();

4 Bit Int (DPT 3)

uint8_t value = telegram->get4BitIntValue();

Bool (DPT 3)

bool value = telegram->get4BitDirectionValue();

1 byte (DPT 3)

uint8_t value = telegram->get4BitStepsValue();

1 Byte int (DTP 5 - 0...255)

int8_t value = telegram->get1ByteIntValue();

1 Byte unsigned int (DTP 5 - 0...255)

uint8_t value = telegram->get1ByteUIntValue();

2 Byte int (DTP 7 - 0…65 535])

int16_t value = telegram->get2ByteIntValue();

2 Byte unsigned int (DTP 7 - 0…65 535])

uint16_t value = telegram->get2ByteIntValue();

2 Byte Float (DPT9 - -671 088,64 to 670 760,96 )

float value = telegram->get2ByteFloatValue();

3 Byte Time (DTP 10)

uint8_t value = telegram->get3ByteWeekdayValue();
uint8_t value = telegram->get3ByteHourValue();
uint8_t value = telegram->get3ByteMinuteValue();
uint8_t value = telegram->get3ByteSecondValue();

3 Byte Date (DTP 11)

uint8_t value = telegram->get3ByteDayValue();
uint8_t value = telegram->get3ByteMonthValue();
uint8_t value = telegram->get3ByteYearValue();

4 byte Float (DTP 14 - -2147483648 to 2147483647)

float value = telegram->get4ByteFloatValue();

14 Byte Text (DTP 16)

String value = telegram->get14ByteValue();

The following links can be helpfull

• https://www.hqs.sbt.siemens.com/cps_product_data/gamma-b2b/PCBA_UP117-12_datasheet.pdf
• https://www.hqs.sbt.siemens.com/cps_product_data/gamma-b2b/TPUART2_technical-data.pdf
• https://sar.informatik.hu-berlin.de/research/publications/SAR-PR-2017-01/SAR-PR-2017-01_.pdf
• https://github.com/franckmarini/KnxDevice