CAN Bus Data Channels

Can Bus Data Channel Properties

Label

Message ID hex

The id of the can bus message that contains the channel information. Can be 11 or 29 bit.

Start Byte

Length

Byte Order

Mask hex

A hexadecimal mask that is applied to the raw channel bytes using a binary AND function.

Sign

Multiplier

Divisor

Used in equation to convert bits to device internal units.
Can also be used to right shift a partial bitfield. ex divisor = 64 is equivalent to >> 6

Offset
Used in equation to convert bits to device internal units.

Compound Format
When enabled the first byte of the message must match the Compound Byte ID for the channel to be decoded
The compound message or message with row counter format is used to allow sending many channels on the same can id.

Internal Units

Defines the bit resolution of the channel value as stored in the device. Ex Temperaturex0.1degC means that each bit is equal to 0.1degC.

Display Units
Defines how the channel value is converted from internal units for display on the device and in the data analysis software.

Decoding Procedure

The device receives a message with an ID that matches the channel ID
A raw value is built using LENGTH bytes starting at START BYTE.
The bytes are ordered according to the BYTE ORDER setting.
The mask is applied. value = raw_value & mask
If the channel is SIGNED then the value is converted to a signed number.
The factors equation is applied: ((value * MULTIPLIER) / DIVISOR) + OFFSET = value in
The final value in Internal Units is stored and logged.
The conversion to display units is done when the value is displayed so it can be changed at any time