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:

0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
Node ID	Function Code	Data length	Upstream 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.	Reserved	error code	CRC	CRC
01~FF	04	0A	00	00	00	00	00	00	00	00		00000000	16 Bit CRC Calculation results	16 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

Addr	Name	Type	Length
0x00	Flow Integer Part	int16_t	1
0x01	Flow Fractional Part × 10,000	int16_t	1
0x02	Velocity Integer Part	int16_t	1
0x03	Velocity Fractional Part	int16_t	1
0x16	Upstream Temperature × 10	int16_t	1
0x17	Downstream Temperature × 10	int16_t	1
0x1B	Forward Totalised Flow × 100	int32_t	2
0x1D	Reverse Totalised Flow × 100	int32_t	2
0x1F	Net Totalised Flow × 100	int32_t	2
0x21	Heat Integer Part	int16_t	1
0x22	Heat Fractional Part × 10,000	int16_t	1

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 :

0	1	2	3	4	5	6	7	8
Node ID	Function Code	Data length	Forward Totalised Flow × 100：32-Bit signed	Forward Totalised Flow × 100：32-Bit signed	Forward Totalised Flow × 100：32-Bit signed	Forward Totalised Flow × 100：32-Bit signed	CRC	CRC
01	04	04	00	12	D6	87	16 Bit CRC result	16 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 Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Flow Integer Part	0x01	0x04	0x00	0x00	0x00	0x01

RX Example(big endian)	Parameter	ID	FUNC	LEN	DATA	DATA	CRC	CRC
Flow Integer Part	1234.5	0x01	0x04	0x02	0x04	0xD2
	-1234.5	0x01	0x04	0x02	0xFB	0x2E

C. Reading Flow Fractional Part *10000 TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Flow Fractional Part *10000	0x01	0x04	0x00	0x01	0x00	0x01

RX Example(big endian)	Parameter	ID	FUNC	LEN	DATA	DATA	CRC	CRC
Flow Fractional Part *10000	1234.5	0x01	0x04	0x02	0x13	0x88
	-1234.5	0x01	0x04	0x02	0xEC	0x78

D. Reading Velocity Integer Part TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Velocity Integer Part	0x01	0x04	0x00	0x02	0x00	0x01

RX Example(big endian)	Parameter	ID	FUNC	LEN	DATA	DATA	CRC	CRC
Velocity Integer Part	12.34	0x01	0x04	0x02	0x00	0x0C
	-12.34	0x01	0x04	0x02	0xFF	0xF4

E. Reading Velocity Fractional Part*100000 TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Velocity Fractional Part*100000	0x01	0x04	0x00	0x03	0x00	0x01

RX Example(big endian)	Parameter	ID	FUNC	LEN	DATA	DATA	CRC	CRC
Velocity Fractional Part*100000	12.34	0x01	0x04	0x02	0x0D	0x48
	-12.34	0x01	0x04	0x02	0xF2	0xB8

F. Reading Upstream Temperature*10 TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Upstream Temperature*10	0x01	0x01	0x04	0x16	0x00	0x01

RX Example(big endian)	Parameter	ID	FUNC	LEN	DATA	DATA	CRC	CRC
Upstream Temperature*10	10.9	0x01	0x04	0x02	0x00	0x6D

G. Reading Downstream Temperature*10 TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Downstream Temperature*10	0x01	0x04	0x00	0x17	0x00	0x01

RX Example(big endian)	Parameter	ID	FUNC	LEN	DATA	DATA	CRC	CRC
Downstream Temperature*10	0.2	0x01	0x04	0x02	0x00	0x02

H. Reading Forward Totalised Flow TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Forward Totalised Flow*100	0x01	0x04	0x00	0x1B	0x00	0x02

RX Example(big endian)	Parameter	ID	FUNC	LEN	DATA	DATA	DATA	DATA	CRC	CRC
Forward Totalised Flow*100	12345.67	0x01	0x04	0x04	0x00	0x12	0xD6	0x87

I. Reading Reverse Totalised Flow TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Reverse Totalised Flow*100	0x01	0x04	0x00	0x1D	0x00	0x02

RX Example(big endian)	Parameter	ID	FUNC	LEN	DATA	DATA	DATA	DATA	CRC	CRC
Reverse Totalised Flow*100	-76543.21	0x01	0x04	0x04	0xFF	0x8B	0x34	0x4F

J. Reading Net Totalised Flow TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Net Totalised Flow*100	0x01	0x04	0x00	0x1F	0x00	0x02

RX Example(big endian)	Parameter	ID	FUNC	LEN	DATA	DATA	DATA	DATA	CRC	CRC
Net Totalised Flow*100	12345.67	0x01	0x04	0x04	0x00	0x12	0xD6	0x87
	-12345.67	0x01	0x04	0x04	0xFF	0xED	0x29	0x79

K. Reading Heat Integer Part TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Heat Integer Part	0x01	0x04	0x00	0x21	0x00	0x01

RX Example(big endian)	Parameter	Return Value	ID	FUNC	LEN	DATA	DATA	CRC	CRC
Heat Integer Part	123.4567	123	0x01	0x04	0x02	0x00	0x7B
	-123.4567	-123	0x01	0x04	0x02	0xFF	0x85

L. Reading Heat Fractional Part*10000 TX / RX Example

TX Example	ID	FUNC	ADDR	ADDR	LEN	LEN	CRC	CRC
Heat Fractional Part*10000	0x01	0x04	0x00	0x22	0x00	0x01

RX Example(big endian)	Parameter	Return Value	ID	FUNC	LEN	DATA	DATA	CRC	CRC
Heat Fractional Part*10000	123.4567	4567	0x01	0x04	0x02	0x11	0xD7
	-123.4567	-4567	0x01	0x04	0x02	0xEE	0x29