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24 March 2016

Windmill Software Ltd
Data Acquisition Intelligence
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Reading Data from NMEA Instruments

Windmill software lets you continually log data from instruments sending out NMEA messages. You can also connect other instruments with RS232, RS485 or TCP/IP serial ports to a PC running Windows. All data is time-stamped and you can send it to Excel either during or after data collection. Alternatively, subscribers to the Monitor newsletter (ISSN 1472-0221) can download free NMEA logging software: ComDebug. This lets you log one channel of data and save it in a text file.

  1. Run the Windmill ComDebug program and enter your instrument's settings.
  2. Use ComDebug to log data from your instrument.
  3. Optionally, run the Windmill DDE Panel, Logger or Chart program to save or display data from your instrument.

Read this page in conjunction with the Getting Started with COMIML, ComDebug and Windmill 7 page. For a fuller guide to NMEA settings see Data Logging from NMEA Devices.

NMEA Instruments

COM Port Settings

You need to tell the ComDebug software about the communication settings you are using. These should work for all instruments but, depending on your device, you may be able to use a higher baud rate.

Comm Port: Select the port to which your instrument is connected.
Baud Rate: 4800
Data Bits: 8
Parity: None
Stop Bits: 1 (or more)
Flow Control: None

Data Format

The NMEA 0183 standard specifies communication in coded sentences in ASCII (text) format. Each sentence begins with the dollar character, $, and ends with a carriage return and a line feed. Between the beginning and the end are identifier and data fields, separated by commas. For example, a line starting $GPGLL tells the software that the following data is geographic position - latitude and longitude.

Example data string: $GPGLL,5330.25,N,00215.31,W,134531,A*2D<CR><LF>
Data format: ASCII
Example parsing: Search for $GPGLL,
Extract Until , (Extracts Latitude)
Search for N,
Extract Until , (Extracts Longitude)

Instrument Timing

Read: In the Background
Timeout: 5000 ms
Instrument Idle or Wait Time: 500 ms
Data Persistence Time: 5000 ms

Further Information:
Data Logging from NMEA Instruments.
Windmill Serial Port Driver Settings
Getting Started with ComDebug and COMIML
COM Port Settings