The dmi1..4 values are speed values in an arbitrary unit. Its resolution must be enough
to produce meaningful measurements from small movements (e.g., mm/s, 0.01km/h,
0.02m/s). Coarse resolutions like kilometers per hour will not work well, particularly at
slow speeds. Thus, we recommend employing millimeters per second as the standard
measurement unit. The dmiX fields can have the following assignments:
• dmi1 is for RC wheel or FR wheel.
• dmi2 is for FL wheel or YW sensor.
• dmi3 is for RR wheel.
• dmi4 is for RL wheel.
The wheelspeed mask is divided into eight fields and determines which of the dmi1..4
values contain valid data and the type of data the value represents. The dmiX_mask
fields can be either 0 or 1, depending on whether the dmiX value is invalid or valid.
The dmiX_type is a 7-bit unsigned integer representing the value type in the dmiX field.
Currently, only two values are supported: 0 for a linear speed or 1 for an angular velocity.
Some example masks:
• 0x00000001 = dmi1 value is valid and represents a linear velocity.
• 0x00000802 = dmi2 value is valid and represents an angular velocity.
• 0x00000004 = dmi3 value is valid and represents a linear velocity.
• 0x02000008 = dmi4 value is valid and represents an angular velocity.
An example message with hexdump of the binary data:
• dmi1 = 111 = 0x0000006f = 6f 00 00 00 (at offset 12).
• dmi2 = -22222 = 0xfffff752 = 32 a9 ff ff (at offset 16).
• dmi3 = 333333 = 0x00051615 = 15 16 05 00 (at offset 20).
• dmi4 = -44 = 0xffffffd4 = d4 ff ff ff (at offset 24).
• mask = 0x00000001 | 0x00000002 | 0x00000004 | 0x00000008 = 0x0000000f = 0f
00 00 00 (at offset 28).
An example of a NOV_B-RAWDMI message is shown below:
Figure 5.21.: NOV_B-RAWDMI example message
Vision-RTK 2 | Fixposition Positioning Sensor 36
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