FieldServer - What is Gray Code – Reflected Binary Code, and how is it used in FieldServers

Gray Code is one of the most important codes. It is a non-weighted code which belongs to a class of codes called minimum change codes. While traversing from one step to another step, only one bit in the code group changes in these types of codes. In the case of Gray Code, two adjacent code numbers differ from each other by only one bit. You will probably understand it better by looking at the table given below.  This code is not applicable in any type of arithmetical operations, but it has some applications in analog to digital converters and in some input/output devices.
 

DecimalBinaryGray Code
000000000
100010001
200100011
300110010
401000110
501010111
601100101
701110100
810001100
910011101
1010101111
1110111110
1211001010
1311011011
1411101001
1511111000


Using Gray Codes in FieldServer Gateways


In the configuration below:

Reads 6 Binary inputs from each of 2 BACnet devices, converts to a Binary (Decimal) Number, and then converts those numbers to Gray Codes, which are served using MSTP
 
Data_Arrays

Data_Array_Name , Data_Format , Data_Array_Length

DA_BitsA        , Bit         , 100

DA_BitsB        , Bit         , 100

DA_Float        , Float       , 100


//================================================================================

//

//    Server Side Connections

//


Adapters

Adapter , Protocol

N1      , Bacnet_IP



//================================================================================

//

//    Server Side Nodes

//

Nodes

Node_Name    , Node_ID , Protocol  ,Node_Option  ,Adapter

SouceNodeA   , 37306   , Bacnet_IP ,COV_disable  ,N1

SouceNodeB   , 37307   , Bacnet_IP ,COV_disable  ,N1


//================================================================================

//

//    Server Side Map Descriptors

//


Map_Descriptors

Data_Type , Object_ID , Map_Descriptor_Name         , Units    , Data_Array_Name , Data_Array_Offset , Node_Name    , Property      , Function

BI        , 0         , Bit 0                       , No_Units , DA_BitsA        , 0                 , SouceNodeA   , Present_Value , rdbc

BI        , 1         , Bit 1                       , No_Units , DA_BitsA        , 1                 , SouceNodeA   , Present_Value , rdbc

BI        , 2         , Bit 2                       , No_Units , DA_BitsA        , 2                 , SouceNodeA   , Present_Value , rdbc

BI        , 3         , Bit 3                       , No_Units , DA_BitsA        , 3                 , SouceNodeA   , Present_Value , rdbc

BI        , 4         , Bit 4                       , No_Units , DA_BitsA        , 4                 , SouceNodeA   , Present_Value , rdbc

BI        , 5         , Bit 5                       , No_Units , DA_BitsA        , 5                 , SouceNodeA   , Present_Value , rdbc

BI        , 6         , Bit 6                       , No_Units , DA_BitsA        , 6                 , SouceNodeA   , Present_Value , rdbc

BI        , 7         , Bit 7                       , No_Units , DA_BitsA        , 7                 , SouceNodeA   , Present_Value , rdbc


Map_Descriptors

Data_Type , Object_ID , Map_Descriptor_Name         , Units    , Data_Array_Name , Data_Array_Offset , Node_Name    , Property      , Function

BI        , 0         , Bit 0                       , No_Units , DA_BitsB        , 0                 , SouceNodeB   , Present_Value , rdbc

BI        , 1         , Bit 1                       , No_Units , DA_BitsB        , 1                 , SouceNodeB   , Present_Value , rdbc

BI        , 2         , Bit 2                       , No_Units , DA_BitsB        , 2                 , SouceNodeB   , Present_Value , rdbc

BI        , 3         , Bit 3                       , No_Units , DA_BitsB        , 3                 , SouceNodeB   , Present_Value , rdbc

BI        , 4         , Bit 4                       , No_Units , DA_BitsB        , 4                 , SouceNodeB   , Present_Value , rdbc

BI        , 5         , Bit 5                       , No_Units , DA_BitsB        , 5                 , SouceNodeB   , Present_Value , rdbc

BI        , 6         , Bit 6                       , No_Units , DA_BitsB        , 6                 , SouceNodeB   , Present_Value , rdbc

BI        , 7         , Bit 7                       , No_Units , DA_BitsB        , 7                 , SouceNodeB   , Present_Value , rdbc



Moves

Source_Data_Array , Source_offset , Target_Data_Array , Target_Offset , Length ,Function

DA_BitsA          , 0             , DA_Float          , 0             , 8      ,Bit_pack

DA_BitsB          , 0             , DA_Float          , 1             , 8      ,Bit_pack




//================================================================================

//

// COnnection

//

adapters,

Adapter, Protocol  ,

N1     , CAS_TOOLN1 ,


//================================================================================

//

//    Client Side Nodes

//


Nodes,

Node_Name, Node , Protocol   ,Adapter

CASUTIL  , 1    , CAS_TOOLN1  ,N1



//================================================================================

//

//    Client Side Map Descriptors

//

//

//

Map_Descriptors

Map_Descriptor_Name ,Scan_Interval ,Data_Array_Name ,Data_Array_Offset ,CAS_TOOLS_Array_Name ,CAS_TOOLS_Array_Offset ,Function ,Node_Name ,CAS_TOOLS_Function_Name       ,Length ,Address

toGray              ,1.0s          ,DA_FLOAT        ,0                 ,DA_FLOAT             ,10                     ,wrbc     ,CASUTIL   ,TO_GRAYCODE                   ,1      ,00

toGray              ,1.0s          ,DA_FLOAT        ,1                 ,DA_FLOAT             ,11                     ,wrbc     ,CASUTIL   ,TO_GRAYCODE                   ,1      ,00

//fromGray            ,1.0s          ,DA_GRAY         ,0                 ,DA_BIN               ,1                      ,wrbc     ,CASUTIL   ,FROM_GRAYCODE                 ,1      ,00

//================================================================================

//

//    Server Side Connections

//


connections

Port, Baud , Parity, Data_Bits, Stop_Bits, Protocol   , Timeout, Connection_Type ,

R2  , 38400, None  , 8        , 1        , Bacnet_MSTP, 30     , MSTP_Master_Node,





//===============================================================================

//

//    Server Side Nodes

//

Nodes

Node_Name        , Node_ID , Protocol    , Node_Option

ServerNode       , 31      , Bacnet_MSTP , COV_Disable




Map_Descriptors

Data_Type , Object_ID , Map_Descriptor_Name         , Units    , Data_Array_Name , Data_Array_Offset , Node_Name    , Property      , Function , Data_Array_Low_Scale , Data_Array_High_Scale , Node_Low_Scale , Node_High_Scale

AI        , 1         , AnalogValue_converted_A     , No_Units , DA_Float        , 0                 , ServerNode   , Present_Value , Server   , 0                    , 100                   , 0              , 100

AI        , 2         , AnalogValue_converted_B     , No_Units , DA_Float        , 1                 , ServerNode   , Present_Value , Server   , 0                    , 100                   , 0              , 100



Sample c++ code

unsigned int bin2Gray(unsigned int num)

{

return (num >> 1) ^ num;

}

unsigned int gray2Bin(unsigned int num)

{

unsigned int mask;

for (mask = num >> 1; mask != 0; mask = mask >> 1)

{

num = num ^ mask;

}

return num;

}


Online Gray Code Converter

http://www.miniwebtool.com/binary-to-gray-code-converter/

http://www.miniwebtool.com/gray-code-to-binary-converter/


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