I am creating a NMEA PGN. Bit filed length is 11. It would appear that you can enter any number between 0 and 9. But only one digit seems allowed contrary to the example above.The bit length of the parameter in its PGN message. The length of the data is
measured in bits.
When the data length is less than 1 byte, this field must be filled. For example,
SPN 899 Engine Torque Mode has a start position of the 1st byte and 1st bit in its
PGN with 4 bits data length. As a result, Start Byte = 1, Start Bit = 1, Byte Length
= 0 and Bit Length = 4 should be inputted for this parameter.
If the data length is greater than 1 byte, users may choose to fill in the data length
in either Byte Length, Bit Length or combined. For example, SPN 190 Engine
Speed has a start position of the 4th byte in its PGN with 16 bits data length. As a
result, Start Byte = 4, Start Bit = 1, Byte Length = 0 and Bit Length = 16 may be
input for this parameter if users prefer.
Bug: Bit Length for NMEA parameter
- JZanni
- Posts: 29
- Joined: Tue Oct 12, 2010 3:09 pm
Bug: Bit Length for NMEA parameter
The documentation page 74 states:
- jpratt
- Enovation Controls Development
- Posts: 222
- Joined: Mon Jun 21, 2010 11:18 am
Re: Bug: Bit Length for NMEA parameter
After chatting with people around here, it appears that this is not something we were expecting. I think the assumption was that any standard PGN's were less than 8 bits when using it as a bit field. I will log this to get corrected in a future release. For now you will probably have to manipulate the data via a script to get the desired effect.
Jake Pratt
Software Development Manager
Software Development Manager
- JZanni
- Posts: 29
- Joined: Tue Oct 12, 2010 3:09 pm
Re: Bug: Bit Length for NMEA parameter
Thanks for the response. So far I was reporting data entry only. I went around by entering the length as being 1 Byte+3 bits hoping the sytem will read this as an 11 bits wide field. I am still developing and I do not know if this will work as I hope. But for NMEA bit field apprently can be as wide as they want. For example NMEA Unique Number is 21Bits. I have seen some as wide as 24 bits. So will 1Byte+3 bits work? If you think not let me know.
JM
JM
- dwills
- Enovation Controls Development
- Posts: 26
- Joined: Fri Jul 30, 2010 8:27 am
Re: Bug: Bit Length for NMEA parameter
Using a length of 1 byte + 3 bits will be seen as a bit field with a length of 3. This won't work. We don't currently have a good way of supporting this, unless you want to create 2 separate varaibles and manipulate the variables with a script to create one with a length of 11 bits. If the data rate for this message is fairly low this shouldn't be too much of a burden on the system.