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{{ :custom_protocols:apator-head-view1.png?250|}}

====== Apator APT-MBU-NA-1C water meter head ======

This head is used for turbine type water flowmeters which is put on the top of the water meter device. 
You can use [[custom_protocols|custom protocol]] feature for reading this device. 

===== Connection setup =====

Please setup connection in WebHMI as follows: 
{{:custom_protocols:apator-conn-setup-page-1.png?800px}}

{{:custom_protocols:apator-conn-setup-page-2.png?800px}}

===== Custom protocol source code =====

<code lua>
POLL_DELAY = 60 -- poll rate constant in sec. 

function DBG(...) ------ convenient print function -----------
    for i = 1, #arg do 
        local curArgument = arg[i]
        if type(curArgument) == 'table' then 
            tprint(curArgument)
        else 
            INFO(curArgument)
        end 
    end 
end 
DEBUG = DBG 

HEX_NUMBERING = 16 -- numbering system conversion 

-- mbus control bytes 
BRDCAST_NET_LAYER_ADDR = 0xFD  -- 253 
BROADCAST_ADDR         = 0xFE  -- 254 

-- delimiters 
SHORT_FRAME_STX     = 0x10
SEND_NKE            = 0x40
ACK                 = 0xE5
ETX                 = 0x16 
CTRL_LONG_FRAME_STX = 0x68
REQ_UD2             = 0x7B -- Request for Class 2 Data 
REQ_UD2_            = 0x5B -- Request for Class 2 Data 


-- PROBE_PACKET = {SHORT_FRAME_STX, REQ_UD2_, 0xFE, 0x59, 0x16}  original 
PROBE_PACKET = {SHORT_FRAME_STX, REQ_UD2_, BROADCAST_ADDR, 0x59, ETX}

REQ_UD2_POS              = 2 
PROBE_PACKET_PAYLOAD_LEN = 2 
PROBE_PACKET_CRC_POS    = 4  

-- 04 13               dif vif signature 
-- 1F 42 0F 00         vol. data example in INT32 
VOL_DIF_VIF = {0x04, 0x13}
VOL_DATA_LEN = 4 

function onScanStart ()
    now = os.time()
end 
 
function createDevices ()
   addDevice{name = "V",     shift = 0, base = 10, xtraFields = {} }
end 

function readRegister (reg, device, unitId)
    
    if (not lastReadTimeStamp or (now - lastReadTimeStamp) >= POLL_DELAY ) then 
    
        PROBE_PACKET[PROBE_PACKET_CRC_POS] = getCRC(PROBE_PACKET, REQ_UD2_POS, PROBE_PACKET_PAYLOAD_LEN)
        
        if (not sendBytes(PROBE_PACKET) ) then
            ERROR("Could not sent bytes for DATA_QUERY!") 
            return false
        end
        
        local meterDataFrame = readUntil(ETX) 
        
        if (#meterDataFrame > 10) then
            local foundDataPos = tableFindPattern(meterDataFrame, VOL_DIF_VIF)
            if foundDataPos then
                lastReadTimeStamp = now 
                local dataChunk = table.sub(meterDataFrame
                                            ,foundDataPos
                                            , foundDataPos + VOL_DATA_LEN - 1)

                local revDataHexStr = tabHexView(reverseTable(dataChunk) )  
                data = tonumber(revDataHexStr, HEX_NUMBERING) 
            else 
                ERROR("failed to find data !")
                data = false     
            end 
        else 
            ERROR("failed to read reply!")
            data = false 
        end 
    end 
    
    return data 
    
end 

function writeRegister (reg, device, unitId, newValue)
end

-------------------------- Helpers --------------------------

function tableFindPattern(inputTab, sequence) -- finds pattern in a table 
    
    for tabIndex, _ in ipairs(inputTab) do 
        
        local matchFlag = true 
        
        for seqIndex, sequenceByte in ipairs(sequence) do  -- checking sequence inside a inputTab 
            matchFlag = matchFlag and (sequenceByte == inputTab[tabIndex + seqIndex - 1])
            if (not matchFlag) then 
                matchFlag = false 
                break
            end 
        end
    
        if matchFlag then 
            return (tabIndex + #sequence) -- start of data 
        end 
    end 

    return false  
end 

function table.sub(t, startIndex, endIndex) -- picks sub-table from a table 
    local tmpTable = {}
    
    for k = startIndex, endIndex do 
        table.insert(tmpTable, t[k])
    end  
    
    return tmpTable
end 

function tabHexView(hextab, spacer) -- get string of a hex view for a table 
    local hex = {} 
    
    for _, hexbyte in ipairs(hextab) do 
        table.insert(hex, getHexByteAsStr(hexbyte))
    end 
    
    return table.concat(hex, spacer)
end 

function getHexByteAsStr(inputByte) -- gets 2 - char hex string of a byte 
    local strByte = string.format("%X", inputByte)    
    return (#strByte == 1 and '0' .. strByte) or strByte
end 

function getCRC(a, pos, len)   -- calc. CRC sum for the mbus packet 
    local sum, mask  = 0, 0xFF
     
    for i = pos, pos + len - 1 do
        sum = sum + a[i] 
        sum = bit.band(sum, mask)
    end 
    return sum
end 

function reverseTable(tab) -- reverses a table 
    local outTable = {}
    for i = #tab, 1, -1 do 
        table.insert(outTable, tab[i])
    end 
    return outTable
end 

function readUntil(endByte) -- read input buffer untils endByte or timeout 
    local ONE_BYTE = 1 
    local buf = {}
    repeat 
        local rxSymbol = readBytes(ONE_BYTE)[ONE_BYTE]
        if rxSymbol then 
            table.insert(buf, rxSymbol)
        end 
    until (not rxSymbol or (rxSymbol == endByte))

    return ((#buf >= ONE_BYTE) and buf) or false 
end </code>