# 7. MODBUS Communication Protocol **Read instantaneous flow rate, flow speed, RSSI, and signal quality:** | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------ | --------- | --------- | ------ | ------ | ------------------------------ | ------------------------------ | | Node ID | Funtion Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 04 | 00 | 00 | 00 | 07 | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | ‌ **Response format:** | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | | ------- | ------------ | ----------- | ------------------------- | ------------------------- | -------------------------- | -------------------------- | -------------------------- | -------------------------- | --------------------------- | --------------------------- | ------------- | --------------- | -------- | -------------- | -------- | --------------- | ------------------------------ | ------------------------------ | | Node ID | Funtion Code | Data length | Integer part of flow rate | Integer part of flow rate | Fraction part of flow rate | Fraction part of flow rate | Integer part of flow speed | Integer part of flow speed | Fraction part of flow speed | Fraction part of flow speed | Upstream RSSI | Downstream RSSI | Reserved | Signal quality | Unit | Metric/Imperial | CRC | CRC | | 01\~FF | 04 | 0D | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | 0 | ​Content | ​Content | ​Content | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | Byte 00 : Node ID‌ Byte 01 : Function code‌ Byte 02 : Data length 10 bytes‌ Byte 03 \~ 04 : Integer part of totalized positive flow rate, Format: 16-bit signed integer‌ Byte 05 \~ 06 : Fraction part of totalized positive flow rate, Format: 16-bit signed integer, divide by 10000 before add to integer part‌ Byte 07 \~ 08 : Integer part of totalized positive flow speed, Format: 16-bit signed integer‌ Byte 09 \~ 10 : Fraction part of totalized positive flow speed, Format: 16-bit signed integer, divide by 10000 before add to integer part‌ Byte 11, 12 : 8-bit unsigned integer, value is between 0 and 100‌ Byte 14 : 8-bit unsigned integer, value is between 0 and 100‌ Byte 15 : 8-bit unsigned integer, convert this number from hexadecimal to decimal, the digit in tens represents the unit of numerator and the digit in ones represents the unit of denominator. The table below shows the corresponding unit for each number.‌ Byte 16 : 8-bit unsigned integer,value is 1 or 2. 1 stands for Metric, 2 stands for Imperial. **Numerator :** | Number | Unit | | ------ | ------------------------ | | 1 | Cubic meter (m³) | | 2 | Liter (l) | | 3 | USA gallon (gal) | | 4 | Imperial Gallon (igl) | | 5 | Million USA gallon (Mgl) | | 6 | Cubic feet (cf) | | 7 | USA liquid barrel (bal) | | 8 | Oil barrel (ob) | ‌ **Denominat :** | Number | Unit | | ------ | ------ | | 1 | Second | | 2 | Minute | | 3 | Hour | | 4 | Day | ‌ **Read totalized positive (forward-direction) flow rate :** | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ------------------------------ | ------------------------------ | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 04 | 00 | 07 | 00 | 05 | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | ‌ **Response format:** | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | | ------- | ------------- | ----------- | -------------------------------------------- | -------------------------------------------- | -------------------------------------------- | -------------------------------------------- | --------------------------------------------- | --------------------------------------------- | --------------------------------------------- | --------------------------------------------- | -------- | -------- | ------------------------------ | ------------------------------ | | Node ID | Function Code | Data length | Integer part of totalized positive flow rate | Integer part of totalized positive flow rate | Integer part of totalized positive flow rate | Integer part of totalized positive flow rate | Fraction part of totalized positive flow rate | Fraction part of totalized positive flow rate | Fraction part of totalized positive flow rate | Fraction part of totalized positive flow rate | Reserved | Unit | CRC | CRC | | 01\~FF | 04 | 0A | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | 0 | ​Content | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | Byte 00 : Node ID‌ Byte 01 : Function code‌ Byte 02 : Data length 10 bytes‌ Byte 03 \~ 06 : 32-bits signed integer‌ Byte 07 \~ 10 : 32-bits signed integer, divide by 1000000 before add to integer part‌ Byte 12 : Value is between 1 and 8. The table below shows the corresponding unit for each number. | Number | Unit | | ------ | ------------------------ | | 1 | Cubic meter (m³) | | 2 | Liter (l) | | 3 | USA gallon (gal) | | 4 | Imperial Gallon (igl) | | 5 | Million USA gallon (Mgl) | | 6 | Cubic feet (cf) | | 7 | USA liquid barrel (bal) | | 8 | Oil barrel (ob) | ‌ **Read totalized negative (reverse-direciton) flow rate:** | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ------------------------------ | ------------------------------ | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 04 | 00 | 0C | 00 | 05 | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | ​‌ **Response format:** | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | | ------- | ------------- | ----------- | -------------------------------------------- | -------------------------------------------- | -------------------------------------------- | -------------------------------------------- | --------------------------------------------- | --------------------------------------------- | --------------------------------------------- | --------------------------------------------- | -------- | -------- | ------------------------------ | ------------------------------ | | Node ID | Function Code | Data length | Integer part of totalized negative flow rate | Integer part of totalized negative flow rate | Integer part of totalized negative flow rate | Integer part of totalized negative flow rate | Fraction part of totalized negative flow rate | Fraction part of totalized negative flow rate | Fraction part of totalized negative flow rate | Fraction part of totalized negative flow rate | Reserved | Unit | CRC | CRC | | 01\~FF | 04 | 0A | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | 0 | ​Content | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | Byte 00 : Node ID‌ Byte 01 : Function code‌ Byte 02 : Data length 10 bytes‌ Byte 03 \~ 06 : 32-bits signed integer‌ Byte 07 \~ 10 : 32-bits signed integer, divide by 1000000 before add to integer part‌ Byte 12 : Value is between 1 and 8. The table below shows the corresponding unit for each number. | Number | Unit | | ------ | ------------------------ | | 1 | Cubic meter (m³) | | 2 | Liter (l) | | 3 | USA gallon (gal) | | 4 | Imperial Gallon (igl) | | 5 | Million USA gallon (Mgl) | | 6 | Cubic feet (cf) | | 7 | USA liquid barrel (bal) | | 8 | Oil barrel (ob) | ‌ **Read totalized net flow rate:** | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------ | --------- | --------- | ------ | ------ | ------------------------------ | ------------------------------ | | Node ID | Funtion Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 04 | 00 | 11 | 00 | 05 | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | ‌ **Response format:** | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | | ------- | ------------- | ----------- | --------------------------------------- | --------------------------------------- | --------------------------------------- | --------------------------------------- | ---------------------------------------- | ---------------------------------------- | ---------------------------------------- | ---------------------------------------- | -------- | -------- | ------------------------------ | ------------------------------ | | Node ID | Function Code | Data length | Integer part of totalized net flow rate | Integer part of totalized net flow rate | Integer part of totalized net flow rate | Integer part of totalized net flow rate | Fraction part of totalized net flow rate | Fraction part of totalized net flow rate | Fraction part of totalized net flow rate | Fraction part of totalized net flow rate | Reserved | Unit | CRC | CRC | | 01\~FF | 04 | 0A | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | ​Content | 0 | ​Content | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | Byte 00 : Node ID‌ Byte 01 : Function code‌ Byte 02 : Data length 10 bytes‌ Byte 03 \~ 06 : 32-bits signed integer‌ Byte 07 \~ 10 : 32-bits signed integer, divide by 1000000 before add to integer part‌ Byte 12 : Value is between 1 and 8. The table below shows the corresponding unit for each number. | Number | Unit | | ------ | ------------------------ | | 1 | Cubic meter (m³) | | 2 | Liter (l) | | 3 | USA gallon (gal) | | 4 | Imperial Gallon (igl) | | 5 | Million USA gallon (Mgl) | | 6 | Cubic feet (cf) | | 7 | USA liquid barrel (bal) | | 8 | Oil barrel (ob) | ‌ **Clear all totalized flow rate:** | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ------------------------------ | ------------------------------ | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 14 | 00 | 00 | 00 | 00 | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | ‌ **Clear totalized net flow rate:** | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ------------------------------ | ------------------------------ | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 15 | 00 | 00 | 00 | 00 | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | ‌ **Clear totalized positive (forward-direction) flow rate:** | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ------------------------------ | ------------------------------ | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 16 | 00 | 00 | 00 | 00 | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | ‌ **Clear totalized negative (reverse-direction) flow rate:** | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ------------------------------ | ------------------------------ | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 17 | 00 | 00 | 00 | 00 | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | ## 7.6 Read upstream and downstream PT1000 temperature, instantaneous flow and error bits: (available starting from fw 1.2.2) Read upstream and downstream PT1000 temperature, instantaneous flow and error bits: | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ------------------------------ | ------------------------------ | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 04 | 00 | 16 | 00 | 05 | 16 Bit CRC Calculation results | 16 Bit CRC Calculation results | Response format:
0123456789101112131415
0123456789101112131415
Node IDFunction CodeData lengthUpstream temperature multiplied by 10, rounded to the nearest integer (format: 16-Bit signed integer multiplied by ten)Upstream temperature multiplied by 10, rounded to the nearest integer (format: 16-Bit signed integer multiplied by ten)Downstream temperature multiplied by 10, rounded to the nearest integer (Format: 16-Bit signed integer multiplied by ten)Downstream temperature multiplied by 10, rounded to the nearest integer (Format: 16-Bit signed integer multiplied by ten)Integer portion of the flow rate (format: 16-Bit signed integer)Integer portion of the flow rate (format: 16-Bit signed integer)Decimal portion of the flow rate (format: 16-Bit signed integer). It needs to be divided by 10000 before being added to the integer portion.Decimal portion of the flow rate (format: 16-Bit signed integer). It needs to be divided by 10000 before being added to the integer portion.Reservederror codeCRCCRC
01~FF040A00000000000000000000000016 Bit CRC Calculation results16 Bit CRC Calculation results
Byte 00 : Node ID‌ Byte 01 : Function code‌ Byte 02 : Data length 8 bytes Byte 03 \~ 04 : Upstream temperature multiplied by 10, rounded to the nearest integer (format: 16-Bit signed integer multiplied by ten) Byte 05 \~ 06 : Downstream temperature multiplied by 10, rounded to the nearest integer (Format: 16-Bit signed integer multiplied by ten) Byte 07 \~ 08 : Integer part of the flow rate, format: 16-Bit signed integer Byte 09 \~ 10 : Decimal portion of the flow rate , format: 16-Bit signed integer, before adding it to the integer portion, divide it by 10000 Byte 12 : error code ## 7.6.1 Resetting Totalised Flow Data： Clear All Totalised Flow Data: | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ----------------- | ----------------- | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 14 | 00 | 00 | 00 | 00 | 16 Bit CRC result | 16 Bit CRC result | Clear Net Totalised Flow: | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ----------------- | ----------------- | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 15 | 00 | 00 | 00 | 00 | 16 Bit CRC result | 16 Bit CRC result | Clear Forward Totalised Flow: | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ----------------- | ----------------- | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 16 | 00 | 00 | 00 | 00 | 16 Bit CRC result | 16 Bit CRC result | Clear Reverse Totalised Flow: | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ----------------- | ----------------- | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01\~FF | 17 | 00 | 00 | 00 | 00 | 16 Bit CRC result | 16 Bit CRC result | ## 7.7 Single Data Read Command (Updated in Firmware 1.2.6) ### 7.7.1 04 Single Data Read - Memory Register List
AddrNameTypeLength
0x00Flow Integer Partint16_t1
0x01Flow Fractional Part × 10,000int16_t1
0x02Velocity Integer Partint16_t1
0x03Velocity Fractional Partint16_t1
0x16Upstream Temperature × 10int16_t1
0x17Downstream Temperature × 10int16_t1
0x1BForward Totalised Flow × 100int32_t2
0x1DReverse Totalised Flow × 100int32_t2
0x1FNet Totalised Flow × 100int32_t2
0x21Heat Integer Partint16_t1
0x22Heat Fractional Part × 10,000int16_t1
### **7.7.2** Read Command Example A. Reading Big Endian Forward Totalised Flow Data (TX) Example Transmission : | **0** | 1 | 2 | 3 | 4 | 5 | 6 | 7 | | ------- | ------------- | --------- | --------- | ------ | ------ | ----------------- | ----------------- | | Node ID | Function Code | Address 1 | Address 0 | Data 1 | Data 0 | CRC | CRC | | 01 | 04 | 00 | 1B | 00 | 02 | 16 Bit CRC result | 16 Bit CRC result | Node ID Byte 01 : Node identifier 01 Function code Byte 01 : Function code 04 Addr Byte 02\~03 : 00 1B (Memory address corresponding to forward totalised flow). Length Byte 05 \~ 06 : 00 02 (corresponding to 2 registers for forward totalised flow ×100). CRC: (Error-checking code).
(RX) Example Response :
01234567815
01234567815
Node IDFunction CodeData lengthForward Totalised Flow × 100：32-Bit signedForward Totalised Flow × 100：32-Bit signedForward Totalised Flow × 100：32-Bit signedForward Totalised Flow × 100：32-Bit signedCRCCRC
0104040012D68716 Bit CRC result16 Bit CRC result
Node ID Byte 00 : Node identifier 01 Function code Byte 01 : Function code 04 Length Byte 02 : 00 04 Data length in 4 bytes Data Byte 03 \~ 06 : 00 12 D6 87 Forward totalised flow ×100 in big endian format (32-bit signed integer). CRC: (Error-checking code). #### B. Reading Flow Integer Part TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Flow Integer Part0x010x040x000x000x000x01
RX Example(big endian)Parameter IDFUNCLENDATADATACRCCRC
Flow Integer Part 1234.50x010x040x020x040xD2
-1234.50x010x040x020xFB0x2E
#### C. Reading Flow Fractional Part \*10000 TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Flow Fractional Part *100000x010x040x000x010x000x01
RX Example(big endian)Parameter IDFUNCLENDATADATACRCCRC
Flow Fractional Part *100001234.50x010x040x020x130x88
-1234.50x010x040x020xEC0x78
#### D. Reading Velocity Integer Part TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Velocity Integer Part0x010x040x000x020x000x01
RX Example(big endian)ParameterIDFUNCLENDATADATACRCCRC
Velocity Integer Part12.340x010x040x020x000x0C
-12.340x010x040x020xFF0xF4
#### E. Reading Velocity Fractional Part\*100000 TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Velocity Fractional Part*1000000x010x040x000x030x000x01
RX Example(big endian)ParameterIDFUNCLENDATADATACRCCRC
Velocity Fractional Part*10000012.340x010x040x020x0D0x48
-12.340x010x040x020xF20xB8
#### F. Reading Upstream Temperature\*10 TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Upstream Temperature*100x010x010x040x160x000x01
RX Example(big endian)ParameterIDFUNCLENDATADATACRCCRC
Upstream Temperature*1010.90x010x040x020x000x6D
G. Reading Downstream Temperature\*10 TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Downstream Temperature*100x010x040x000x170x000x01
RX Example(big endian)ParameterIDFUNCLENDATADATACRCCRC
Downstream Temperature*100.20x010x040x020x000x02
#### H. Reading Forward Totalised Flow TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Forward Totalised Flow*1000x010x040x000x1B0x000x02
RX Example(big endian)ParameterIDFUNCLENDATADATADATADATACRCCRC
Forward Totalised Flow*10012345.670x010x040x040x000x120xD60x87
#### I. Reading Reverse Totalised Flow TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Reverse Totalised Flow*1000x010x040x000x1D0x000x02
RX Example(big endian)ParameterIDFUNCLENDATADATADATADATACRCCRC
Reverse Totalised Flow*100-76543.210x010x040x040xFF0x8B0x340x4F
#### J. Reading Net Totalised Flow TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Net Totalised Flow*1000x010x040x000x1F0x000x02
RX Example(big endian)ParameterIDFUNCLENDATADATADATADATACRCCRC
Net Totalised Flow*10012345.670x010x040x040x000x120xD60x87
-12345.670x010x040x040xFF0xED0x290x79
#### K. Reading Heat Integer Part TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC

Heat Integer Part

0x010x040x000x210x000x01
RX Example(big endian)ParameterReturn ValueIDFUNCLENDATADATACRCCRC

Heat Integer Part

123.45671230x010x040x020x000x7B
-123.4567-1230x010x040x020xFF0x85
#### L. Reading Heat Fractional Part\*10000 TX / RX Example
TX ExampleIDFUNCADDRADDRLENLENCRCCRC
Heat Fractional Part*100000x010x040x000x220x000x01
RX Example(big endian)ParameterReturn ValueIDFUNCLENDATADATACRCCRC
Heat Fractional Part*10000123.456745670x010x040x020x110xD7
-123.4567-45670x010x040x020xEE0x29