Moire Labs MODBUS Protocol Version 1
Please mind, that not all registers are supported on all device types.
Accessing RAM
READ function 0x03 (16 bit words) / 0x46 (bytes)
WRITE function 0x10 (16 bit words) / 0x47 (bytes)
Using functions 0x03 and 0x10 reads and writes MODBUS address in word-lengths (2 bytes). This means, that defining MODBUS register to read must always be even. On the other hand, functions 0x46 and 0x47 reads and writes data in byte-lengths (1-byte), which makes it more flexible to access data which would otherwise be padded. The following tables show both register addresses - either accessible through word address or byte address.
Fnc 0x03/0x10 Fnc 0x46/0x47 Description Value type address [DEC] address [DEC] 0 0 Filtered value of primary ADC (RO) 32bit float 2 4 Filtered value of secondary ADC (RO) 32bit float 4 8 Output DAC (RO) 16bit int 5 10 Raw primary value without correction (RO) 32bit float 7 14 Raw secondary value (RO) 32bit float 9 18 Primary measurement value (RO) 32bit float 11 22 Secondary measurement value (RO) 32bit float 13 26 Output value (RO) 32bit float 17 34 Primary value without autozero correction (RO) 32bit float - 55 measurement_interval_hours (RW) uint8_t 28 56 measurement_interval_minutes (RW) uint8_t - 57 measurement_interval_seconds (RW) uint8_t RO denotes read-only register, RW denotes read-write register.
Example of reading from RAM
Requesting 2x 16 bit registers (4 bytes) from device number 1 starting on index 9 using function 0x03. CRC is 0x1409.
=> 01 03 0009 0002 1409 This is the same as: => 01 46 0018 0004 09C1
In both cases the device will return 4 bytes (2 registers), which are the primary measurement value and shall be interpreted as 32-bit float.
Accessing ROM / EEPROM
READ 16-bit words function: 0x41
READ 8-bit bytes function: 0x44
WRITE 16-bit words function: 0x42
WRITE 8-bit bytes function: 0x45
Using functions 0x41 and 0x42 reads and writes MODBUS address in word-lengths (2 bytes). This means, that defining MODBUS register to read must always be even. On the other hand, functions 0x44 and 0x45 reads and writes data in byte-lengths (1-byte), which makes it more flexible to access data which would otherwise be padded. The following tables show both register addresses - either accessible through word address or byte address.
Fnc 0x41/0x42 Fnc 0x44/0x45 Description Value type address [DEC] address [DEC] 0 0 Protocol (0:MODBUS RTU; 1:SDI12) (RW) uint8_t - 1 Databits (0:5, 1:6, 2:7, 3:8) (RW) uint8_t 1 2 Parity (0:none, 1:even, 2:odd) (RW) uint8_t - 3 Stopbits (0:1, 1:2) (RW) uint8_t 2 4 Baud rate (in baud/s) (RW) uint32_t 4 8 MODBUS address (RW) uint8_t - 121 Primary reading minimum (RO) 32bit float - 125 Primary reading maximum (RO) 32bit float - 14561 Scale factor of primary reading (RO) uint8_t 7281 14562 Unit of primary reading (RO) uint8_t - 14563 Scale factor of secondary reading (RO) uint8_t 7282 14564 Unit of secondary unit (RO) uint8_t 7362 14724 Location ID (RW) uint16_t 7363 14726 Sensor ID (RO) uint32_t 7365 14730 Measurements per packet (RW) uint8_t 7368 14736 Primary measurement type (RO) uint8_t 7369 14738 Measurement ID (RW) uint8_t RO denotes read-only register, RW denotes read-write register.
Example of writing to ROM
Writing 1 byte of value 0xAA to device number 1 starting on index 8 using function 0x45.
=> 01 45 0008 0001 01 AA A4ED 0008 = start index to write to 0001 = number of 8-bit bytes to write 01 = number of bytes which follow in this packet
Writing 4 bytes of value 0xAABBCCDD to device number 1 starting on index 2 using function 0x42. CRC is 0x1409.
=> 01 42 0002 0002 04 AABBCCDD 1459 00002 = start index to write to 0002 = number of 16-bit registers to write 04 = number of bytes which follow in this packet
Measurement type lookup table
Pressure Absolute (against vacuum) 0 Pressure Relative (against atmosphere (gauge pressure)) 1 Temperature 2 Binary (open / close; yes / no; 1 / 0) 3 Pulses 4
Units of measurements and scale factors lookup tables
Units
°K - Kelvin (temperature) = 0 °C - Celsius (temperature) = 1 °Ré - Réaumur (temperature) = 2 °F - Fahrenheit (temperature) = 3 °R - Rankine (temperature) = 4 Pa - Pascal (pressure) = 5 bar (pressure) = 6 atm (pressure) = 7 torr (pressure) = 8 mmHg (pressure) = 9 psi (pressure) = 10 m (level) = 11 reserved = 12 m3 (volume) = 13 l (volume) = 14 m3/s (flow) = 15 m3/h (flow) = 16 l/s (flow) = 17 l/h (flow) = 18 A (current) = 19 V (voltage) = 20 % (humidity) = 21
Unit scale factors
This is the unit scale factor. For example, if the unit is Pa and the scale factor is KILO, then the reading is in kPa.
no scale factor = 0 a (atto) = 1 f (femto) = 2 p (piko) = 3 n (nano) = 4 u (mikro) = 5 m (mili) = 6 c (centi) = 7 d (deci) = 8 da (deka) = 9 h (hekto) = 10 k (kilo) = 11 M (Mega) = 12 G (Giga) = 13 T (Tera) = 14 P (Peta) = 15 E (exa) = 16