The FlexRay decoder I/O decodes analog data on a bus to FlexRay message data. FlexRay uses a differential signal on the bus, FlexRay BP (Bus Plus) and FlexRay BM (Bus Minus). The decoder must be connected to this differential signal, either measured using a scope with a differential input or by measuring both signals individually with single-ended inputs and subtracting them from each other with an Add / Subtract I/O. The FlexRay decoder has auto baud rate detection.
The output of the FlexRay decoder I/O can be shown in a Table sink. It can also be used by the Value extractor I/O to extract a specific value from it to be displayed in a graph, meter or table.
The following fields are extracted from the FlexRay communication and shown as a column in the table:
| Field name | Purpose | Default shown |
|---|---|---|
| Frame ID (Hex) | Frame Identifier in hexadecimal notation | |
| Frame ID (Dec) | Frame Identifier in decimal notation | |
| Cycle count | Cycle count | |
| Header CRC (Hex) | CRC of the header in hexadecimal notation | |
| Header CRC valid | Flag indicating whether the header CRC is valid | |
| Data (Hex) | The data in hexadecimal notation | |
| Data CRC (Hex) | CRC of the data in hexadecimal notation | |
| Data CRC valid | Flag indicating whether the header CRC is valid | |
| Valid | Indicating the FlexRay message is valid | |
| Flags | Flags regarding the FlexRay message |
To show or hide specific columns from the table, use the Select columns
(
) button
in the Table sink.
Double clicking a row in the table will zoom the active graph in to the time frame corresponding to the table row.
The Value extractor I/O can be used to extract a specific value from the decoded data and present that in a graph, a meter or a table.
Measurement on a FlexRay bus, with data decoded by a FlexRay decoder.
FlexRay decoder properties
To control the behavior of the FlexRay decoder I/O, several properties and actions are available.
These can be accessed through a popup menu which is shown when the I/O is right clicked in the Object screen.
The properties can also be accessed through its settings window which is shown when the I/O is double clicked in the Object screen.
To open the Object screen, click the 
Show object screen button.
By default, the settings window only shows the most used settings. When Advanced is ticked, the extended window with all settings is shown. See also the program settings.
Level
In order to decode the analog signal into a digital signal, the FlexRay decoder I/O compares the analog input signal with a mid level: anything above that level is considered "high" and anything below that level is considered "low".
Hysteresis
To minimize the effect of noise on the signal when comparing the signal to the level, a Hysteresis can be used around that level. Anything above "level + hysteresis/2" is considered "high" and anything below "level - hysteresis/2" is considered "low".
Invert
For correct detection, the Invert property must be set to the correct value, corresponding to the bus that is under measurement.
- When Invert is disabled levels above signal mid level are logic 0, levels below signal mid level are logic 1
- When Invert is enabled levels above signal mid level are logic 1, levels below signal mid level are logic 0
Invert is default off.
Baud rate
For correct detection, the Baud rate property must be set to the correct value corresponding to the bus that is under measurement. It can be set to several common standard values, but it is also possible to enter an arbitrary value in the Baud rate edit field.
Auto detect baud rate
Enabling Auto detect baud rate will let the software determine the correct baud rate, based on the measured signal. Each time new data is available, the baud rate will be determined again. Auto detect baud rate is default enabled.
Snap to standard baud rate
When Auto detect baud rate is enabled, the setting Snap to standard baud rate will set the baud rate to the closest standard baud rate (from the baud rate list) if the determined value is within 1 % of this standard value. Snap to standard baud rate is default enabled.
Channel
A FleyRay communication contains 2 channels, Channel A and Channel B. Usually only one channel is used. The decoder can select one channel to decode the data from.
Auto detect channel
Enabling Auto detect channel lets the software detect which channel is being used.
