Documentation of CAN messages

CMM-2CH and CMM-3CH can be controlled via CAN-FD. Each measurement channel has its own microcontroller. The nominal baudrate is 1 MBit/s, the data baudrate is 4 MBit/s. A DBC file is available on the download page.

Structure of CAN-IDs

The CAN IDs are build with the following scheme.

Bit	Mask	Content	Comment
28	0x10000000	Direction	0: PC to uC, 1: uC to PC
27-20	0x0FF00000	Command-ID	0...255 see section Commands
19-12	0x000FF000	Module-ID	"M" = 0x4D
11-4	0x00000FF0	Board-ID	0...31 (Can be set via DIP switch on CMM-2CH), 255 = 0xFF = broadcast to all boards
3-0	0x0000000F	Channel-ID	0...2 (Is hardwired on CMM-xCH), 15 = 0xF = broadcast to all channels

The highest value of board (0xFF) and channel (0xF) is used as broadcast. For example the ID 0x 0 00 4D 01 F is the command "SetOnOff" (= 0x01) for all channels on board 1.

List of CAN-Commands

Physical values are always transmitted as float (32 Bit / Single Precision / LSB first) and in the base unit (V / A / sec / °C / ... ).

CAN-IDs to set and get register style values

Get-ID and Response-ID are the same, because the already differ in the direction bit 28. The command values in the following table include the direction bit, to make this clear.

Set-ID	Get-ID	Response-ID	Command	DLC	Data
-	-	0x140	CommandResponse	2	StatusCode (U8), Command (U8)
0x001	0x041	0x141	OnOff	1	OnOff [0/1] (U1)
0x002	-	-	OnOffSelected	1	EnableMask_Board (U8)
0x003	0x043	0x143	MinRange	1	MinRange (U8)
0x004	0x044	0x144	MinMaxAvg	24	CurrentMin [A] (float), CurrentAvg [A] (float), CurrentMax [A] (float),
					VoltageDropMax [V] (float), NoOfSamples (U32), RangeMin (U8), RangeMax (U8)
0x005	0x045	0x145	ChannelConfig	5	OnOffDefaultValue [0/1] (U1), MeasuredValuesInterval [sec] (float)
0x006	0x046	0x146	CanConfig	3	TxFrameFormat [Enum] (U8), NominalBaudrate [Enum] (U8), DataBaudrate [Enum] (U8)
0x007	0x047	0x147	LegacyConfig	16	LocalId (U32), LocalIdIsExt (U1),RemoteId (U32), RemoteIdIsExt (U1)
					LegacyCyclicId (U32), LegacyCyclicIdIsExt (U1), LegacyCyclicMessageEnable (U1)
-	0x048	0x148	Version	12	HardwareType (U8), FirmwareVersion (U16), CompileTimestamp (U32),
					WarningRegister (U16), HardwareVersion (U8)
-	0x049	0x149	SerialNumber	12	SerialNumber (String 12 Bytes)
0x00A	-	-	RestoreDefault	0	-
0x00D	0x04D	0x14D	DisableCalibration	1	DisableCalibration [0/1] (U1)

Status codes

Code	Description
0xA0	Success
0xE0	Unknown command
0xE1	Invalid DLC
0xE2	Parameter out of range
0xE3	Flash error
0xE4	Flash verify error
0xE5	Command not allowed
0xE6	Firmware hardware mismatch
0xE7	File not found

Values in WarningRegister

Name	Value
WARNING_CANRXFIFOFULL	0x0001
WARNING_CANTXFIFOFULL	0x0002
WARNING_CANBUSOFF	0x0004
WARNING_INVALIDCALIBRATION	0x0008
WARNING_DISABLEDCALIBRATION	0x0010
WARNING_ISOTPRXFIFOFULL	0x0020

Cyclic CAN-IDs uC -> PC

Physical values are always transmitted as float (32 Bit / Single Precision / LSB first) and in the base unit (V / A / sec / °C / ... ).

Command-ID	Name	DLC	Data
0x180	MeasuredValues	12	Current [A] (float), Range (U8), VoltageDrop [V] (float), OnOff [0/1] (U1)
0x18E	ErrorHandler	48	ErrorType (U8), FileNumber (U8), LineNumber (U16), more info