Introduction

This binding for openHAB has ability to connect directly DIY devices (based on Arduino or whatever else). Binding uses serial communication or network communication over implemented TCP server.

Used protocol is easy to implement. Implementation examples for Arduino over serial, STM8, ESP8266 over TCP is part of repository. Arduino IDE library is also available.

Compiled binding is inserted into release branch: https://github.com/docbender/openHAB-SimpleBinary/releases

Binding is working with openHAB 1.8 as well as with openHAB2 in 1.x compatibility mode.

Serial port

It is possible to configure several ports not only one. At one line it is possible to connect several devices (ready for RS422/RS485).

Binding sets the serial port speed according to user configuration. Other parameters are set as follows: 8 data bits, 1 stop bit, without parity and without flow control.

Flow control (especially for RS-485 converters) can be provided through RTS pin. This can be turned on by adding forceRTS parameter in binding port configuration. If it is required inverted function of RTS pin, forceRTSInv parameter should be added in configuration instead forceRTS.

Communication can operate in 2 data read modes - OnScan and OnChange.

TCP server

At binding startup TCP server start listening on user defined port. In basic 256 clients are supported. Every connected client gets actual items states after device ID verification.

Known limitations: max.256 clients(protocol limitation).

Operating modes

Communication can operate it 2 modes reading data from connected devices - OnScan and OnChange. In OnScan mode all data are reading cyclically. In OnChange mode only new data are sent to openHAB. Each device is polled whether has new data and then sends new data to openHAB. One of his modes must be choose in serial port connection. TCP server connection not use any of these modes as default. Because TCP connection is full-duplex, spontaneous states send is preferred and expected.

Supported data types

Binding support openHAB data types listed in the table. Individual item types are converted to simple data types such as byte, word, double word, float, array, rgb. For same types may be converted type defined, others has it strictly defined. Supported data types

Item type	Supported data type	Notes
Number	byte, word, dword, float	Numbers are represented in signed form. Their maximum value depends on the used type. Floating point number is represented by float type. Float is stored in 4 bytes formatted according to IEEE 754.
Color	hsb, rgb, rgbw	All color parts are transferred in one double word. Each color component corresponds to one byte. Assignment of bytes depending on the chosen data type is following: HSB - byte 0 - Hue, 1 - Saturation , 2 - Brightness, 3 - Not used RGB - byte 0 - Red, 1 - Green, 2 - Blue, 3 - Not used RGBW - byte 0 - Red, 1 - Green, 2 - Blue, 3 - White
String	array	Array of bytes. Length of array is specified in square brackets behind type definition (e.g. array[32] defines byte array with length 32 bytes)
Contact	byte	0 - off, 1 - on
Switch	byte	0 - off, 1 - on
Dimmer	byte
Rollershutter	word	Lower byte for position, upper byte for StopMove/UpDown command - 1-Move,2-Stop,4-Up,8-Down

Binding configuration

In openhab.cfg is binding configured this way:

################################### SimpleBinary Binding ######################################
#
# Select port (ex.: COM1:115200;onscan;forceRTSInv or /dev/ttyUSB1:9600). It is possible defined 
# more ports ex. port1, port2,port145,... Behind semicolon you can specify data pool control (optional).    
# Options for reach slave data are onchange(ask configured devices for new data - default) 
# or onscan(read all data every scan). Option forceRTS or forceRTSInv are for trigger RTS signal
# during data send (useful for RS485 converter). 
# TCP server is defined by tcpserver key. As value server port must be defined.
# 
# serial port configuration
simplebinary:port=COM4:9600;onchange
# TCP server configuration
simplebinary:tcpserver=43243
#refresh - check for new data interval - default 10000ms 
simplebinary:refresh=2000

Configuration parameter	Description
port	Serial port definition. Configuration value consist from port name and bitrate (COM1:9600, /dev/ttyS2:57600). Behind semicolon optional parameters can be specified. Pool control (onchange, onscan) Enable RTS signal handling (forceRTS or forceRTSInv for signal inversion) Multiple port can be specified. Must be deviate by number behind key (ex.: port, port1, port123,...)
tcpserver	TCP server definition. As value listening port must be specified.
refresh	Execution period [ms] between reading cycles. Default 10000ms.

Item configuration

Binding specify item configuration is located as usual in the brackets at the end of the configuration line. It consists of three compulsory and two optional parameters.

Configuration format:

simplebinary="port name:device address:item address:[used data type]:[direction]"

Configuration parameter	Description
port name	Port name that is specified in binding configuration in openhab.cfg. For simplebinary:port= port name is port. For simplebinary:port1= port name is port1. For simplebinary:tcpserver= port name is tcpserver.
device address	The device address is number that device is indicated on the bus (for RS485 and ethernet)
item address	It is the address under which the data is stored in the target device.
used data type	Optional. Allow define data type. See table Supported data types
direction	Optional. Can be I - input, O - output or IO - both (default). It is used only for request data from connected devices. So if all device items are outputs only, there would be no requesting for data from device. It is also good to define data direction for inter-device communication items.

Example of binding configuration:

Dimmer    Item01    "Value[%d]"    { simplebinary="port:1:1" }
Number    Item02    "Value[%d]"    { simplebinary="port:1:3:dword:IO" }
Number    Item03    "Value[%f]"    { simplebinary="port:1:4:float:O" }
Number    Item04    "Value[%f]"    { simplebinary="port:1:14:float:I" }
String    Item05    "Value[%s]"    { simplebinary="port:2:1:array[32]:O" }
Color     TestColor01              { simplebinary="tcpserver:2:2:rgb:O" }

Inter-device communication

Binding support inter-device communication. To configure this another device/binding can be specified separated by comma in item configuration. In examples values from first device are written into openHAB (input-I direction) and same value is immediately written into second device (output-O direction):

Number    Temperature    "Value[%f]"    { simplebinary="port:1:1:float:I", simplebinary="tcpserver:1:1:float:O" }
Number    TemperatureCPU "Value[%f]"    { exec="<[/bin/cat /sys/class/thermal/thermal_zone0/temp:30000:JS(divideTemp.js)]", simplebinary="tcpserver:1:2:float:O" }    

Diagnostic item configuration

Binding itself offers some diagnostic states. There are available statuses for communication port itself and also statuses for connected devices. These statuses can be provided into openHAB if they are properly configured (by use configuration parameter info behind port name or device address).

Port diagnostic info configuration format:

simplebinary="port name:info:port status"

Port statuses:

Status	Description	Returned values
state	Return current port status.	0 - Unknown 1 - Listening (opened and ready) 2 - Closed 3 - Not exist 4 - Not available (probably used)
previous_state	Return previous port status	Same as state
state_change_time	Return time when status was changed	DateTime value

Device diagnostic info configuration format:

simplebinary="port name:device address:info:device status"

Device statuses:

Status	Description	Returned values
state	Return current device status.	0 - Unknown 1 - Connected and answering 2 - Not responding / disconnected 3 - Response error (device still wants repeat query - received message had bad CRC) 4 - Data error (device report unknown item address, unknown data, unsupported message or error while saving delivered data)
previous_state	Return previous device status	Same as state
state_change_time	Return time when status was changed	DateTime value
packet_lost	Return percentage of packet lost (not delivered, bad CRC, ...) within last 5 minutes	0-100%

Example of diagnostic item configuration:

Number    PortState            "Port state [%s]"                 { simplebinary="port:info:state" }
Number    PortPreviouState     "Port previous state [%s]"        { simplebinary="port:info:previous_state" }
DateTime  PortStateChangeTime  "Port changed [%1$tA, %1$td.%1$tm.%1$tY %1$tT]"    { simplebinary="port:info:state_change_time" }

Number    Dev01State           "Device 1 state [%s]"             { simplebinary="port:1:info:state" }
Number    Dev01PreviouState    "Device 1 previous state [%s]"    { simplebinary="port:1:info:previous_state" }
DateTime  Dev01StateChangeTime "Device 1 changed [%1$tA, %1$td.%1$tm.%1$tY %1$tT]" { simplebinary="port:1:info:state_change_time" }
Number    Dev01PacketLost      "Device 1 packet lost rate [%s]"  { simplebinary="port:1:info:packet_lost" }

Number    Dev02State           "Device 2 state [%s]"             { simplebinary="port:2:info:state" }
Number    Dev02PreviouState    "Device 2 previous state [%s]"    { simplebinary="port:2:info:previous_state" }
DateTime  Dev02StateChangeTime "Device 2 changed [%1$tA, %1$td.%1$tm.%1$tY %1$tT]" { simplebinary="port:2:info:state_change_time" }
Number    Dev02PacketLost      "Device 2 packet lost rate [%s]"  { simplebinary="port:2:info:packet_lost" }

Protocol

Binding implements master/slave communication model for serial communication. OpenHAB binding is master and connected devices are slaves. Master sends command and waits for response from slave. Answer should arrived in order tens of milliseconds. However bindings has 2000ms timeout to receive answer. Communication protocol itself depends on requested operating mode of the device (OnScan / OnChange). Of course device can support both operating modes.

Network TCP connection use same protocol as serial communication but in producer/consumer communication model. When client is connected, "Hi" message must be send. Then server can verify and register device ID.

Every packet start with device address and is followed by message type. Minimum packet length is 4 bytes. Packets are secured with CRC8 which should be enough for short packets.

###Master query for new data - OnChange mode On this packet master expecting as answer "data" packet or "no data" packet (message type 0xE2).

Byte	Value	Description
0	0xXX	Device slave address
1	0xD0	Message type
2	0xXX	Control byte. Supported values: 0 - standard (data check only) 1 - force all data request
3	CRC8

Control byte of this packet can says type of new data retrieve: * _Standard_ (value 0) - only really new data are requested. * _Force all data_ (value 1) - that device should mark all his data as new and send it to master. This message master send when there was connection lost between devices. That because meantime data could be changed, openHAB or device restarted, ....

###Master query for data with specified address - OnScan mode On this packet master expecting as answer "data" packet or "invalid address" packet (message type 0xE4).

Byte	Value	Description
0	0xXX	Device slave address
1	0xD1	Message type
2	0xXX	Data address - low byte
3	0xXX	Data address - high byte
4	CRC8

###Data packet for data type byte This "data" packet could be send by master to write data into slave or by slave as answer for data request. Answer from slave should "done" when everything was right.

Byte	Value	Description
0	0xXX	Device slave address
1	0xDA	Message type
2	0xXX	Data address - low byte
3	0xXX	Data address - high byte
4	0xXX	Data
5	CRC8

###Data packet for data type word This "data" packet could be send by master to write data into slave or by slave as answer for data request. Answer from slave should "done" when everything was right.

Byte	Value	Description
0	0xXX	Device slave address
1	0xDB	Message type
2	0xXX	Data address - low byte
3	0xXX	Data address - high byte
4	0xXX	Data - low byte
5	0xXX	Data - high byte
6	CRC8

###Data packet for data type dword This "data" packet could be send by master to write data into slave or by slave as answer for data request. Answer from slave should "done" when everything was right.

Byte	Value	Description
0	0xXX	Device slave address
1	0xDC	Message type
2	0xXX	Data address - low byte
3	0xXX	Data address - high byte
4	0xXX	Data - 1. byte (lowest)
5	0xXX	Data - 2. byte
6	0xXX	Data - 3. byte
7	0xXX	Data - 4. byte (highest)
8	CRC8

###Data packet for type HSB, RGB, RGBW This "data" packet could be send by master to write data into slave or by slave as answer for data request. Answer from slave should "done" when everything was right.

Byte	Value	Description
0	0xXX	Device slave address
1	0xDD	Message type
2	0xXX	Data address - low byte
3	0xXX	Data address - high byte
4	0xXX	Data - 1. byte (lowest)
5	0xXX	Data - 2. byte
6	0xXX	Data - 3. byte
7	0xXX	Data - 4. byte (highest)
8	CRC8

###Data packet for type array This "data" packet could be send by master to write data into slave or by slave as answer for data request. Answer from slave should "done" when everything was right.

Byte	Value	Description
0	0xXX	Device slave address
1	0xDE	Message type
2	0xXX	Data address - low byte
3	0xXX	Data address - high byte
4	0xXX	Data length - low byte
5	0xXX	Data length - high byte
6	0xXX	Data
...	0xXX	Data
n-1	CRC8

###Acknowledge packet - Done Answer from slave that data write from master was accepted.

Byte	Value	Description
0	0xXX	Device slave address
1	0xE0	Message type
2	0x00
3	CRC8

###Error packet - Repeat Answer that received packet had wrong CRC. On this packet master react by sending last packet again (max. 3 time).

Byte	Value	Description
0	0xXX	Device slave address
1	0xE1	Message type
2	0xXX	Here is expected CRC8 calculated by slave (master logged it for comparison).
3	CRC8

###Acknowledge packet - No new data Slave react with this packet on query for new data in OnChange mode in case that there's no data to send.

Byte	Value	Description
0	0xXX	Device slave address
1	0xE2	Message type
2	0x00
3	CRC8

###Error packet - Unknown data Slave react with this packet if received message had unknown/unsupported type.

Byte	Value	Description
0	0xXX	Device slave address
1	0xE3	Message type
2	0x00
3	CRC8

###Error packet - Unknown address Slave react with this packet if received message had unknown data item address.

Byte	Value	Description
0	0xXX	Device slave address
1	0xE4	Message type
2	0x00
3	CRC8

###Error packet - Error while saving data Slave send this packet when he could not save received data from master.

Byte	Value	Description
0	0xXX	Device slave address
1	0xE5	Message type
2	0x00
3	CRC8

###Hi packet This packet is for connection model producer/consumer (TCP client/server connection). Client sends this packet after he is connected to server.

Byte	Value	Description
0	0xXX	Device address
1	0xE6	Message type
2	0x00
3	CRC8

###Welcome packet This packet is for connection model producer/consumer (TCP client/server connection). Server sends this packet as Hi packet response.

 

Byte	Value	Description
0	0xXX	Device address
1	0xD2	Message type
2	0xXX	Assigned address
3	CRC8

###Deny packet This packet is for connection model producer/consumer (TCP client/server connection). Server sends this packet as Hi packet response.

 

Byte	Value	Description
0	0xXX	Device address
1	0xD3	Message type
2	0x00
3	CRC8

###Want all data This packet is sent by device to tell that he want's all his data. In master/slave configuration it could be send as response for new data request (0xD0). Note: all data are normally sent when device is connected.

Byte	Value	Description
0	0xXX	Device address
1	0xE7	Message type
2	0x00
3	CRC8

##Implementation The extent of implementation depends on the required features and data types (see chapter Protocol).

At first device should check if message is correctly received (CRC check). Secondly device should check if message is for him by compare message address and his own assigned address. If the address is different device must not respond! Otherwise device must response in corresponding way (see chapter Protocol).

##Implementation example Implementation example for Arduino can be found in Arduino library repo folder.

It consists of two main classes. Class simpleBinary which contains protocol implementation itself and class itemData which provides item data storage and handling with item.

Class simpleBinary - public methods

	simpleBinary(int uartAddress, int size) Constructor. Parameters: uartAddress - device address at communication line, size - number of exchanged items
void	initItem(int indexAndAddress, itemType type, void (*pFce)(itemData*)) Initilize item. Parameters: indexAndAddress - item index in configuration array and also item address used during communication, type - item data type, last parameter is pointer to function that is executed on data receive(NULL for no action).
void	processSerial() Process data received by UART.
bool	checkAddress(int address) Check if address exist in items array. Parameters: address - item address used during communication
void	readData(int address) Read data on given address and send it to master. Parameters: address - item address used during communication
bool	saveByte(int address, char* data) Save byte from given data pointer to addresed item. Return false if target is not expected data type. Parameters: address - item address used during communication, data - pointer to data to save.
bool	saveWord(int address, char* data) Save word from given data pointer to addresed item. Return false if target is not expected data type. Parameters: address - item address used during communication, data - pointer to data to save.
bool	saveDword(int address, char* data) Save double word from given data pointer to addresed item. Return false if target is not expected data type. Parameters: address - item address used during communication, data - pointer to data to save.
bool	saveArray(int address, char *pData, int len) Save byte array from given data pointer to addresed item. Return false if target is not expected data type. Parameters: address - item address used during communication, pData - pointer to data to save, len - array length (byte count)
int	size() Return items count.
void	enableRTS(int pinNumber) Enable RTS handling. RTS pin is passed as parameter.
void	setSendDelay(unsigned int delayms) Sets delay between receive and transmit message (in ms). Good for communication line stabilization.

Class itemData - public methods

	itemData() Constructor.
	itemData(int address, itemType type, void (*pFce)(itemData*) ) Constructor with item initialization . Parameters: address - item address used during communication, type - item data type, last parameter is pointer to function that is executed on data receive(NULL for no action).
	itemData(int address, itemType type, int size, void (*pFce)(itemData*) ) Constructor with item initialization for arrays. Parameters: address - item address used during communication, type - item data type, size - data size in bytes, last parameter is pointer to function that is executed on data receive(NULL for no action).
void	init(int address, itemType type, void (*pFce)(itemData*)) Item initialization . Parameters: address - item address used during communication, type - item data type, last parameter is pointer to function that is executed on data receive(NULL for no action).
bool	saveByte(char* data) Save byte from given data pointer. Return false if target is not expected data type. Parameters: data - pointer to data to save.
bool	saveWord(char* data) Save word from given data pointer. Return false if target is not expected data type. Parameters: data - pointer to data to save.
bool	saveDword(char* data) Save double word from given data pointer. Return false if target is not expected data type. Parameters: data - pointer to data to save/td>
bool	saveArray(char *pData, int len) Save array from given data pointer. Return false if target is not expected data type. Parameters: data - pointer to data to save, len - array length (byte count)
void	save(int value) Save int value. Parameters: value - value to save
void	save(float value) Save float value. Parameters: value - value to save
int	getAddress() Return item address.
void	setNewData() Set item "new data" flag.
bool	hasNewData() Check if item has "new data" flag set.
char*	getData() Return item data.
char*	readNewData() Return item data and reset "new data" flag.
itemType	getType() Return item data type.
int	getDataLength() Return length of data.
void	executeAction() Execute action connected at item initialization.

###CRC8 calculation implementation

char CRC8::evalCRC(char *data, int length)
{
   int crc = 0;
   int i, j;

   for(j=0; j < length; j++)
   {
      crc ^= (data[j] << 8);
	
      for(i=0;i<8;i++)
      {
         if((crc & 0x8000) != 0)
            crc ^= (0x1070 << 3);
	
         crc <<= 1;
      }
   }	
   return (char)(crc >> 8);
}