> For the complete documentation index, see [llms.txt](https://docs.irs.systems/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.irs.systems/cmm-2ch/general/can-protocol-en.md).

# 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](https://downloads.irs.systems/?sku=12).

## Structure of CAN-IDs

The CAN IDs are build with the following scheme.

<table><thead><tr><th width="89">Bit</th><th width="137.66668701171875">Mask</th><th width="131.3333740234375">Content</th><th>Comment</th></tr></thead><tbody><tr><td>28</td><td>0x10000000</td><td>Direction</td><td>0: PC to uC, 1: uC to PC</td></tr><tr><td>27-20</td><td>0x0FF00000</td><td>Command-ID</td><td>0...255 see section <a href="#list-of-can-commands">Commands</a></td></tr><tr><td>19-12</td><td>0x000FF000</td><td>Module-ID</td><td>"M" = 0x4D</td></tr><tr><td>11-4</td><td>0x00000FF0</td><td>Board-ID</td><td>0...31 (Can be set via DIP switch on CMM-2CH), 255 = 0xFF = broadcast to all boards</td></tr><tr><td>3-0</td><td>0x0000000F</td><td>Channel-ID</td><td>0...2 (Is hardwired on CMM-xCH), 15 = 0xF = broadcast to all channels</td></tr></tbody></table>

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.

<table><thead><tr><th width="80">Set-ID</th><th width="80.66668701171875">Get-ID</th><th width="110">Response-ID</th><th width="174.3333740234375">Command</th><th width="61">DLC</th><th>Data</th></tr></thead><tbody><tr><td>-</td><td>-</td><td>0x140</td><td>CommandResponse</td><td>2</td><td>StatusCode (U8), Command (U8)</td></tr><tr><td>0x001</td><td>0x041</td><td>0x141</td><td>OnOff</td><td>1</td><td>OnOff [0/1] (U1)</td></tr><tr><td>0x002</td><td>-</td><td>-</td><td>OnOffSelected</td><td>1</td><td>EnableMask_Board (U8)</td></tr><tr><td>0x003</td><td>0x043</td><td>0x143</td><td>MinRange</td><td>1</td><td>MinRange (U8)</td></tr><tr><td>0x004</td><td>0x044</td><td>0x144</td><td>MinMaxAvg</td><td>24</td><td>CurrentMin [A] (float), CurrentAvg [A] (float), CurrentMax [A] (float),</td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>VoltageDropMax [V] (float), NoOfSamples (U32), RangeMin (U8), RangeMax (U8)</td></tr><tr><td>0x005</td><td>0x045</td><td>0x145</td><td>ChannelConfig</td><td>5</td><td>OnOffDefaultValue [0/1] (U1), MeasuredValuesInterval [sec] (float)</td></tr><tr><td>0x006</td><td>0x046</td><td>0x146</td><td>CanConfig</td><td>3</td><td>TxFrameFormat [Enum] (U8), NominalBaudrate [Enum] (U8), DataBaudrate [Enum] (U8)</td></tr><tr><td>0x007</td><td>0x047</td><td>0x147</td><td>LegacyConfig</td><td>16</td><td>LocalId (U32), LocalIdIsExt (U1),RemoteId (U32), RemoteIdIsExt (U1)</td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>LegacyCyclicId (U32), LegacyCyclicIdIsExt (U1), LegacyCyclicMessageEnable (U1)</td></tr><tr><td>-</td><td>0x048</td><td>0x148</td><td>Version</td><td>12</td><td>HardwareType (U8), FirmwareVersion (U16), CompileTimestamp (U32),</td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>WarningRegister (U16), HardwareVersion (U8)</td></tr><tr><td>-</td><td>0x049</td><td>0x149</td><td>SerialNumber</td><td>12</td><td>SerialNumber (String 12 Bytes)</td></tr><tr><td>0x00A</td><td>-</td><td>-</td><td>RestoreDefault</td><td>0</td><td>-</td></tr><tr><td>0x00D</td><td>0x04D</td><td>0x14D</td><td>DisableCalibration</td><td>1</td><td>DisableCalibration [0/1] (U1)</td></tr></tbody></table>

#### Status codes

<table><thead><tr><th width="134.00006103515625">Code</th><th>Description</th></tr></thead><tbody><tr><td>0xA0</td><td>Success</td></tr><tr><td>0xE0</td><td>Unknown command</td></tr><tr><td>0xE1</td><td>Invalid DLC</td></tr><tr><td>0xE2</td><td>Parameter out of range</td></tr><tr><td>0xE3</td><td>Flash error</td></tr><tr><td>0xE4</td><td>Flash verify error</td></tr><tr><td>0xE5</td><td>Command not allowed</td></tr><tr><td>0xE6</td><td>Firmware hardware mismatch</td></tr><tr><td>0xE7</td><td>File not found</td></tr></tbody></table>

#### 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 / ... ).

<table><thead><tr><th width="117.66668701171875">Command-ID</th><th width="172">Name</th><th width="85">DLC</th><th>Data</th></tr></thead><tbody><tr><td>0x180</td><td>MeasuredValues</td><td>12</td><td>Current [A] (float), Range (U8), VoltageDrop [V] (float), OnOff [0/1] (U1)</td></tr><tr><td>0x18E</td><td>ErrorHandler</td><td>48</td><td>ErrorType (U8), FileNumber (U8), LineNumber (U16), more info</td></tr></tbody></table>


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