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Forum Index : Microcontroller and PC projects : Maximite GPS 5hz logger gps18
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vk4tec Senior Member  Joined: 24/03/2012 Location: AustraliaPosts: 239 |
Hello I have successfully used the GPS-mod with Duinomite as an sd card GPS logger at 1 hz Got a maximite now Garmin GPS 18 5 hz Should be ok ? TTL inverted nmea data 19k2 5 volts from maximite Andrew Andrew Rich VK4TEC www.tech-software.net |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
what are the pinouts on a maximite non colour CON9 - IDC connector looking for GND 5V Serial RX TX GPS - Andrew - Andrew Rich VK4TEC www.tech-software.net |
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centrex Guru  Joined: 13/11/2011 Location: AustraliaPosts: 320 |
Andrew You could look up the details here. http://geoffg.net/maximite.html centrex Cliff |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
Thanks Found it GPS18 15 Hz is TTL PC compatible not UART compatible. Andrew Rich VK4TEC www.tech-software.net |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6098 |
The maximite serial ports are 5V tolerant so that is not a problem. You may need to put a simple inverter in to get the polarity correct. Jim VK7JH MMedit MMBasic Help |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
I did some more work on this one GARMIN GPS18 5Hz is TTL PC compatible I used a MAX232 to turn the logic upside down. I have tried a 1Hz GPS and a 5 Hz GPS logging to SD CARD I found the 5 Hz was a bit much for the PIC to keep up with for reading from serial and then writing to SD CARD. The 1 Hz works ok, but it did bomb out not being able to write to the SD card once I will experiement more open "COM2:19200,1024" as #1 ( 1kb buffer ) I know the 5 Hz is loosing data because it normally has Time : .0 Time : .2 Time : .4 Time : .6 Time : .8 The display on the VGA shows some missing lines. I will play some more and report back. I am using COM2 under DM MMBasic 4.0B - Andrew - Andrew Rich VK4TEC www.tech-software.net |
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MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
19200 baud is about 1920 characters per second. How long are the individual messages? Maybe 19200 baud is too low. Microblocks. Build with logic. |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
I have a question about file handles I was open file for append and close sd card file each time a new nmea line came in. But it is also possible to open the file and leave it open and simply append to the file without closeing it each time a new gps line comes in Is there any chance of loss of data if you don't keep closing the file off ? What does open and close file actually do ? It there any performance to be gained from opening the file once instead of open and close all the time ? Andrew vk4tec Andrew Rich VK4TEC www.tech-software.net |
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| MicroBlocks Guru Joined: 12/05/2012 Location: ThailandPosts: 2209 |
Opening and closing files is a performance hit. Even on a 2Ghz PC it can be noticeable. You could buffer a certain amount of data and then write that in one go. If you have a 1k buffer for the com port, you might also buffer about 1k of data before appending it to the file. Microblocks. Build with logic. |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3194 |
> Is possible to open the file and leave it open and simply append to the file without closeing it each time a new gps line comes in? Yes, that would work fine. > Is there any chance of loss of data if you don't keep closing the file off ? If you do not close the file and there is a power failure you could easily end up with a corrupted file or worse a corrupted SD card. > What does open and close file actually do ? Opening a file involves reading the file structure into a memory buffer which is updated as the file is written to. Closing closing the file will write the file structure back to the SD card. It there any performance to be gained from opening the file once instead of open and close all the time ? > Yes, it is faster but the time involved in opening/appending/closing is not great. Especially as you are only logging data once a second. The bigger issue would be the wear on the SD card flash memory. Opening and closing a file causes a rewrite of the FAT and if you do that once a second you could wear out the card in a few weeks. Geoff Geoff Graham - http://geoffg.net |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
I am using some code that does this 1. Get a character from the serial port 2. See if it is a "*" is so, close of the string we have reached the end of the line 3. See if it is a "," is so, we have grabbed the next arg$ Something like this $GPRMC,000009.000,A,2720.2450,S,15302.5998,E,0.00,340.05,080 412,,,A*7B Each character and each comma is interpretted. Very labour intensive If the a input$ syntax that just lets be "grab a line" All I am really intested is the whole lines that BEGIN with GPRMC GPGGA - Andrew - Andrew Rich VK4TEC www.tech-software.net |
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| vk4tec Senior Member Joined: 24/03/2012 Location: AustraliaPosts: 239 |
I am trying LINE INPUT - Andrew - Andrew Rich VK4TEC www.tech-software.net |
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