Get Started with Writing Timetable Data to MDF Files
This example shows how to write timetable data into an MDF file. The MAT-file used in this example MDFTimetables.mat contains two timetables.
Timetable
TT1has variables of numeric data types, including uint8, uint16, uint32, uint64, int8, int16, int32, int64, single, and double.Timetable
TT2has variables of string and byte array data types, including both fixed-length and variable-length data.
Introduction
A simplified model to represent the structure of an ASAM MDF file is a three-level hierarchy composed of the file, the channel group, and the channel. A file consists of a number of channel groups; a channel group consists of a number of channels.
There are two important elements to the content of an MDF file: the data and the metadata.
Signal or channel data written into an MDF file is generally either acquired or calculated. Typical signals for an automotive application are sensor data, ECU-internal variables/states, bus traffic in a vehicle network, or internally calculated values. In most applications, data in all channels of a channel group is synchronized by time, but it is also possible for them to be synchronized by angle, distance, or index. In rare cases, there could be no synchronization domain or multiple synchronization domains. Currently, the MDF functions in MATLAB® only support one synchronization domain by time.
Metadata are additional descriptive information about the measurement environment. They are applicable to the three hierarchical levels: the file, the channel group and the channel. Each level has a set of metadata fields defined by the ASAM MDF standard.
In this example, data in TT1 and TT2 are written into channel groups 1 and 2, respectively, of a new MDF file. You should use this workflow if there is no need to customize metadata at any of the three hierarchical levels.
If you need to customize metadata when writing to an MDF file, use the advanced workflow in example Customize Metadata When Writing Timetable Data to MDF Files.
Load Timetables into Workspace
Load the timetable variables, TT1 and TT2, from MDFTimetables.mat into the workspace.
load("MDFTimetables.mat")Write Timetable Data Directly to a New MDF File
Use the mdfWrite function with the target MDF file name and the timetable variable TT1 specified as input arguments. Because the target file TimetableBasic.mf4 does not exist yet, the function creates the file automatically and displays a warning to inform the path of the newly created file. Data in TT1 is written to the first available channel group index of the file, which is channel group 1 since TimetableBasic.mf4 is a newly created file.
mdfWrite("TimetableBasic.mf4", TT1)Warning: Specified target file did not exist. Created file: /tmp/Bdoc25a_2864802_1971459/tpcbc94420/vnt-ex65847646/TimetableBasic.mf4
Call mdfWrite again to write TT2 to the next available channel group index 2.
mdfWrite("TimetableBasic.mf4", TT2)Examine the Default File Metadata
Using this workflow, default values for file metadata were applied by mdfWrite while creating the MDF file. To examine the file metadata of TimetableBasic.mf4, call mdfInfo with the MDF file name specified.
info = mdfInfo("TimetableBasic.mf4")info =
MDFInfo with properties:
File Details
Name: "TimetableBasic.mf4"
Path: "/tmp/Bdoc25a_2864802_1971459/tpcbc94420/vnt-ex65847646/TimetableBasic.mf4"
Author: ""
Department: ""
Project: ""
Subject: ""
Comment: ""
Version: "4.20"
InitialTimestamp: 2025-02-01 19:16:43.000000000
Creator Details
ProgramIdentifier: "MATLAB"
CreatorVendorName: "The MathWorks, Inc."
CreatorToolName: "MATLAB"
CreatorToolVersion: "25.1.0.2847070 (R2025a) Prerelease Update 3"
CreatorUserName: ""
CreatorComment: ""
File Contents
Attachment: [0×7 table]
ChannelGroupCount: 2
Event: [0×8 eventtable]
Examine the Channel Group Metadata
Examine metadata for the two channel groups written to TimetableBasic.mf4 using mdfChannelGroupInfo. Metadata fields such as AcquisitionName and Comment were assigned default values. Other fields such as NumSamples, DataSize and Sorted are dependent on the data.
chanGrpInfo = mdfChannelGroupInfo("TimetableBasic.mf4")chanGrpInfo=2×13 table
GroupNumber AcquisitionName Comment NumSamples DataSize Sorted SourceName SourcePath SourceComment SourceType SourceBusType SourceBusChannelNumber SourceSimulated
___________ _______________ ___________ __________ ________ ______ ___________ ___________ _____________ ___________ _____________ ______________________ _______________
1 <undefined> <undefined> 100 5000 true <undefined> <undefined> <undefined> Unspecified Unspecified 0 false
2 <undefined> <undefined> 10 340 true <undefined> <undefined> <undefined> Unspecified Unspecified 0 false
Examine the Channel Metadata
Examine metadata for the channels in channel group 1 using mdfChannelInfo. Specify the AdditionalMetadata option as true to view the additional metadata as well.
Row times of the timetable were written into a time channel, while variables of the timetable were written into respective data channels.
Metadata fields Type, DataType and NumBits were derived from the data stored in the corresponding timetable variable by mdfWrite. For instance, variable named uint8_data in TT1 contains 8-bit unsigned integers, so Type of the channel is asam.mdf.ChannelType.FixedLength (0), DataType is asam.mdf.ChannelDataType.IntegerUnsignedLittleEndian (0), and NumBits is 8.
Other metadata fields were assigned default values by mdfWrite. In the case of the time channel, Unit is known to be second, so it was assigned value 's'.
chanGrp1Info = mdfChannelInfo("TimetableBasic.mf4", GroupNumber=1, AdditionalMetadata=true)chanGrp1Info=11×25 table
Name GroupNumber GroupNumSamples GroupAcquisitionName GroupComment GroupSourceName GroupSourcePath DisplayName Unit Comment ExtendedNamePrefix SourceName SourcePath Type SyncType DataType NumBits ComponentType CompositionType ConversionType SourceComment SourceType SourceBusType SourceBusChannelNumber SourceSimulated
_____________ ___________ _______________ ____________________ ____________ _______________ _______________ ___________ ___________ ___________ __________________ ___________ ___________ ___________ ________ ___________________________ _______ _____________ _______________ ______________ _____________ ___________ _____________ ______________________ _______________
"Time" 1 100 <undefined> <undefined> <undefined> <undefined> "" s <undefined> <undefined> <undefined> <undefined> Master Time RealLittleEndian 64 None None Unspecified "" Unspecified Unspecified 0 false
"double_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None RealLittleEndian 64 None None Unspecified "" Unspecified Unspecified 0 false
"int16_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None IntegerSignedLittleEndian 16 None None Unspecified "" Unspecified Unspecified 0 false
"int32_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None IntegerSignedLittleEndian 32 None None Unspecified "" Unspecified Unspecified 0 false
"int64_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None IntegerSignedLittleEndian 64 None None Unspecified "" Unspecified Unspecified 0 false
"int8_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None IntegerSignedLittleEndian 8 None None Unspecified "" Unspecified Unspecified 0 false
"single_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None RealLittleEndian 32 None None Unspecified "" Unspecified Unspecified 0 false
"uint16_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None IntegerUnsignedLittleEndian 16 None None Unspecified "" Unspecified Unspecified 0 false
"uint32_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None IntegerUnsignedLittleEndian 32 None None Unspecified "" Unspecified Unspecified 0 false
"uint64_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None IntegerUnsignedLittleEndian 64 None None Unspecified "" Unspecified Unspecified 0 false
"uint8_data" 1 100 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None IntegerUnsignedLittleEndian 8 None None Unspecified "" Unspecified Unspecified 0 false
Similarly, examine the metadata for channels in channel group 2. Metadata fields Type, DataType and NumBits were also derived from the data stored in the corresponding timetable variable by mdfWrite.
Data samples in variables
fixed_length_string_dataandfixed_length_byte_array_dataofTT2are fixed-length, soTypeof these two channels areasam.mdf.ChannelType.FixedLength(0). Variablesvariable_length_string_dataandvariable_length_byte_array_datacontain data samples with variable lengths, soTypeof these two channels areasam.mdf.ChannelType.VariableLength(1).For the two variables that have string data,
fixed_length_string_dataandvariable_length_string_data,DataTypeisasam.mdf.ChannelDataType.StringASCII(6). For the two variables that have byte array data,fixed_length_byte_array_dataandvariable_length_byte_array_data,DataTypeisasam.mdf.ChannelDataType.ByteArray(10).NumBitsfor a fixed-length channel is derived from the data. For a variable-length channel,NumBitshas a default value of 64.
chanGrp2Info = mdfChannelInfo("TimetableBasic.mf4", GroupNumber=2, AdditionalMetadata=true)chanGrp2Info=5×25 table
Name GroupNumber GroupNumSamples GroupAcquisitionName GroupComment GroupSourceName GroupSourcePath DisplayName Unit Comment ExtendedNamePrefix SourceName SourcePath Type SyncType DataType NumBits ComponentType CompositionType ConversionType SourceComment SourceType SourceBusType SourceBusChannelNumber SourceSimulated
_________________________________ ___________ _______________ ____________________ ____________ _______________ _______________ ___________ ___________ ___________ __________________ ___________ ___________ ______________ ________ ________________ _______ _____________ _______________ ______________ _____________ ___________ _____________ ______________________ _______________
"Time" 2 10 <undefined> <undefined> <undefined> <undefined> "" s <undefined> <undefined> <undefined> <undefined> Master Time RealLittleEndian 64 None None Unspecified "" Unspecified Unspecified 0 false
"fixed_length_byte_array_data" 2 10 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None ByteArray 40 None None Unspecified "" Unspecified Unspecified 0 false
"fixed_length_string_data" 2 10 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> FixedLength None StringASCII 40 None None Unspecified "" Unspecified Unspecified 0 false
"variable_length_byte_array_data" 2 10 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> VariableLength None ByteArray 64 None None Unspecified "" Unspecified Unspecified 0 false
"variable_length_string_data" 2 10 <undefined> <undefined> <undefined> <undefined> "" <undefined> <undefined> <undefined> <undefined> <undefined> VariableLength None StringASCII 64 None None Unspecified "" Unspecified Unspecified 0 false
Examine the Data
To verify that data was successfully written to file, read data from both channel groups using mdfRead and examine the results.
data = mdfRead("TimetableBasic.mf4")data=2×1 cell array
{100×10 timetable}
{ 10×4 timetable}
chanGrp1Data = data{1}chanGrp1Data=100×10 timetable
Time uint8_data uint16_data uint32_data uint64_data int8_data int16_data int32_data int64_data single_data double_data
_______ __________ ___________ ___________ ___________ _________ __________ __________ __________ ___________ ___________
0 sec 0 200 600 1400 -99 -198 -396 -794 -9.8 -19.6
0.1 sec 2 204 608 1416 -97 -194 -388 -778 -9.6 -19.2
0.2 sec 4 208 616 1432 -95 -190 -380 -762 -9.4 -18.8
0.3 sec 6 212 624 1448 -93 -186 -372 -746 -9.2 -18.4
0.4 sec 8 216 632 1464 -91 -182 -364 -730 -9 -18
0.5 sec 10 220 640 1480 -89 -178 -356 -714 -8.8 -17.6
0.6 sec 12 224 648 1496 -87 -174 -348 -698 -8.6 -17.2
0.7 sec 14 228 656 1512 -85 -170 -340 -682 -8.4 -16.8
0.8 sec 16 232 664 1528 -83 -166 -332 -666 -8.2 -16.4
0.9 sec 18 236 672 1544 -81 -162 -324 -650 -8 -16
1 sec 20 240 680 1560 -79 -158 -316 -634 -7.8 -15.6
1.1 sec 22 244 688 1576 -77 -154 -308 -618 -7.6 -15.2
1.2 sec 24 248 696 1592 -75 -150 -300 -602 -7.4 -14.8
1.3 sec 26 252 704 1608 -73 -146 -292 -586 -7.2 -14.4
1.4 sec 28 256 712 1624 -71 -142 -284 -570 -7 -14
1.5 sec 30 260 720 1640 -69 -138 -276 -554 -6.8 -13.6
⋮
chanGrp2Data = data{2}chanGrp2Data=10×4 timetable
Time fixed_length_string_data fixed_length_byte_array_data variable_length_string_data variable_length_byte_array_data
_____ ________________________ ____________________________ ___________________________ _______________________________
0 sec "abcd" {[255 255 255 255 255]} "zero" {[ 255 255]}
1 sec "efgh" {[ 18 35 52 69 86]} "one" {[ 18 35 52 69 86]}
2 sec "ijkl" {[ 0 1 2 3 4]} "two" {[ 0 1 2 3 4 5 6 7]}
3 sec "mnop" {[ 4 3 2 1 0]} "three" {[ 4 3 2 1 0]}
4 sec "qrst" {[255 254 253 252 251]} "four" {[ 253 252 251]}
5 sec "uvwx" {[250 249 248 247 246]} "five" {[250 249 248 247 246]}
6 sec "yzAB" {[245 244 243 242 241]} "six" {[245 244 243 242 241]}
7 sec "CDEF" {[240 239 238 237 236]} "seven" {[ 240 238 236]}
8 sec "GHIJ" {[235 234 233 232 231]} "eight" {[ 235 233 231]}
9 sec "KLMN" {[255 255 255 255 255]} "nine" {[255 255 255 255 255]}
