nmea peculliar problem

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kabouras_33
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nmea peculliar problem

Post by kabouras_33 »

Goodday to all!!
So as i am still working on the same project and i am almost at the end.Ofcourse since i am a very bad luck person for my self i stumbled in hopefully the last problem.
So i will try to explain my situation and any ideas would be very helpfull as always.

So i have a setup which includes a pc that has a nmea simulator called nema studio.
The nema studio is configured to transmit gps packets at every 0.50-1.50 seconds.
The pc is connected with ethernet cable to a rs422 converter and from there using DN8921 ic differential line driver enters my PIC18F46K80 which is configured at 4800 baud rate with a 20Mhz crystal and configuted at HS (16Mhz-25Mhz).
The programm is very simple Uart initialize,loop while (1),Receive char(0),send char.
I have a Multiplexer device which essentialy receives any nmea siglal and disply it to the pc through usb connection and a windows programm that this device has.
And now my problem.

I transmit only 1 line of nmea at 1 sec through the contoller ....nothing pass through but if i change the transmission time from my pc (after the converter) to 0.09 sec then it pass :shock:
Now if i connect the pc (after the converter) directly to the multiplexer at any transmission time it pass correctly.

Now if i choose to transmit lets say 7 lines at 1 sec i can see 6 passing through my pic the 7 will pass through only at 0.09 sec...

Any assistance once again would be great.

Note: i try to use a circular buffer ( same result )
i tried eeprom ( same result )
i tried interupt (same result )
I thought maybe pic speed is too fast so it cannot detect the so small data but only at high speed so i tried the above but nothing!!!

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Re: nmea peculliar problem

Post by kabouras_33 »

If someone needs more informations kindly let me know i will provide as necessary.
I realize this is a weird problem

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Re: nmea peculliar problem

Post by kabouras_33 »

Ok so i guess that the problem is too difficult or i do not provide enough informations.
I will try the afternoon to use interrupts

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Re: nmea peculliar problem

Post by kabouras_33 »

Nothing same result... :evil: :evil: :evil:

kersing
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Re: nmea peculliar problem

Post by kersing »

First of all, to make things clear for us, could you draw a picture of the setup? I think I understand your setup but might well be mistaken.

Second, why do you think this is a problem with your code? Have you tried (now I'm assuming I understood you setup) connecting the output of the DN8921 to the PC input to see if data arrives without issues?
“Integrity is doing the right thing, even when no one is watching.”

― C.S. Lewis

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Re: nmea peculliar problem

Post by kabouras_33 »

First of all thank you very much for the respond and the guidance.
Ok in the afternoon i will take a small video of the setup with pictures and upload
I connected the output directly to pc using hyperterminal and it looks that i receive data but the characters are unrecognisable i will use a max232 and try.
After i ll take the video and photos i will upload all data!
Thanks again!

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