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RACELOGIC Support Centre

Recording and Replaying RS232 Data

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This page contains information about recording and replaying RS232 data with LabSat 4 Record & Replay variants.

LabSat 4 Record & Replay variants (LabSat 4 and LabSat 4 Core) can record and replay RS232 data in addition to GNSS signal data.

Model Limitations

LabSat 4 Lite models cannot record or replay RS232 data.

There are two methods you can use to record RS232:

  • A digitized mode where LabSat 4 samples the raw logic level transitions of the RS232 data and reconstructs the signal during replay
  • The log file mode, where LabSat 4 receives each RS232 data byte and stores the data in a readable text file.
     

Readable RS232 data.png

In either mode, the RS232 signal is converted from the normal signal levels of approximately ± 12 V down to 3 V logic levels to match the internal logic of LabSat 4.

You can use log file mode and digitize mode simultaneously to record data and then choose whether to replay it as digitized or as logged data.

You can see the differences between the Digitized mode and the Log File mode below:

  Strengths Weaknesses
Digitized Mode
  • No need to configure baud rate
  • Very accurate timing
  • Handles binary data
  • No readable log file
Log File Mode
  • Produces readable text file with time stamping
  • Files can be modified to produce test conditions
  • Does not support binary message data
  • Original message timing is not perfectly reproduced
Digitized 

In digitized mode, the data level is sampled and stored in synchronisation with the recorded GNSS data. When replayed, the levels are recreated and output via a voltage level shifter to the RS232 output of LabSat 4. The benefit of this method is that you are not required to configure the baud rate. You can also use this method to capture binary data that does not use the ASCII format.

 
Recording
  1. Connect the RS_Rx and GRN ports of the expansion connector to the appropriate wires/cable.
  2. Connect the expansion connector to Expansion port on the rear panel of LabSat 4.
  3. Power up LabSat 4.
  4. Navigate to the Digital section of the menu. Select the RS232 option.

    Menu -> Setup -> Digital -> CH1/CH2/CH3/CH4 -> RS232
     
  5. Exit the menu.
  6. Press the REC button on the front of LabSat 4 to start the recording.

    LabSat 4 will record all available serial messages.

LabSat4_Recording_LogFile_750px.png

 
Replaying
  1. Connect from the RS_Tx and GRN ports on the LabSat 4 expansion connector to the relevant wires/port on the device under test.
  2. Connect the expansion connector to the Expansion port on the rear panel of LabSat 4.
  3. Select the previously recorded RS232 scenario file and press the Play button on the front of LabSat 4 to start the playback.

LabSat4_Replaying_LogFile_750px.png

Log File 

Log File mode is suitable for recording ASCII text-based message data. As data is received, a new time-stamped line is created in a log file which has the same name as the GNSS signal data but with a .ser extension. Each byte of incoming data is added to the line until LabSat 4 recognises a carriage return [CR] or a line feed [LF] character. On receiving a CR, LF or both characters together, a new line is started in the text file with a new timestamp for the next received character.
 

ASCII Hex Dec Use
<CR> 0x0d 13 Carriage return
<LF> 0x0a 16 Line feed, end delimiter


An example of an ASCII formatted message would be NMEA data from a GNSS module:
 

$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47


Because Log File data is received and processed by LabSat 4, you must configure the correct data or baud rate on LabSat 4. The standard rate for NMEA is 4800 bit/s, but it is not uncommon for systems to use other rates such as 9600 or 115,200 bit/s.
 

RS232-2.PNG
Example of a log file
 

The first section of the log file contains details such as the serial number of LabSat 4, the date and time of recording and the baud rate settings. After the [TIME] and character heading, the received data will appear along with the timestamp of the start of each line.

When you replay a recording with logged RS232 data, LabSat 4 uses the timestamp in the file to replay each line at the corresponding time.

Note: There will be some variation in data output timing when compared to the record timing.

Once a Log File has been created, you can modify the log file by using a text editor application such as Notepad to change the replayed output.

 
Recording 
  1. Connect the RS_Rx and GRN ports of the expansion connector to the appropriate wires/cable.
  2. Connect the expansion connector to Expansion port on the rear panel of LabSat 4.
  3. Power up LabSat 4. 
  4. Navigate to RS232 Log File option.

    Menu -> Setup -> RS232 -> Log File
     
  5. Press the OK button with Log File highlighted to enable it. 
  6. Exit the menu.
  7. Press the REC button on the front of LabSat 4 to start the recording.

    LabSat 4 will record all available serial messages.

LabSat4_Recording_LogFile_750px.png

 
Replaying 
  1. Connect from the RS_Tx and GRN ports on the LabSat 4 expansion connector to the relevant wires/port on the device under test.
  2. Connect the expansion connector to the Expansion port on the rear panel of LabSat 4.
  3. Power up LabSat 4 and navigate to the RS232 menu:

    Menu -> Setup -> RS232 -> REPLAY Log File
     
  4. Press the OK button with REPLAY Log File highlighted to enable it. 
  5. Exit the menu.
  6. Highlight the required scenario file and press the Play button on the front of LabSat 4 to start the playback.

LabSat4_Replaying_LogFile_750px.png

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