polling information in rs-232

[Tondunard]

Hi all,

i'm new to your community and in search of a (probably) simple answer to my problem.

pardon my inexperience, but to learn i guess the best way is to start asking for help (after doing a big search everywhere; OF COURSE ).


my problem:

i have a strip of data from a gps unit in NMEA

$GPGGA,150126,4521.3660,N,07317.9876,W,1,03,102.3, ,,-032.30,M,,*1D

i use a 16f877a (to receive it's no problem)

the problem is that i want to re-send that information ($GPGGA, etc....) every second while i still watch the next incoming data.

here's a simple example:

' This will set the serial port 4800
DEFINE HSER_RCSTA 90h
DEFINE HSER_TXSTA 20h
DEFINE HSER_BAUD 4800
GPS VAR byte
char var byte


main:
' receive from GPS unit
Hserin [char] ' <- works!
GPS = GPS + char '<<<< that part is causing the problem >>>>
' send to computer
hserout [GPS]
goto main:

what i really want to achieve is that the part "hserout [char]" would transmit to the PC every second while i still check the incoming "Hserin [char]" from GPS unit

i know there might be a much simpler way to do this, so i need a bit of your experience please.

Tried to lower the baudrate, tried with interrupt, etc... the "GPS = GPS + char" cause some garble characters in the receiving process...
If i use a LOOP in the "hserout [GPS]" i prevent the reception of new data from GPS unit.

there might be a way while reading the RECREG , but i don't know how....


Awaiting your help

[skimask]

Are you trying to receive the whole string at one time and retransmit the same whole string at once?

GPS = GPS + char '<<<< that part is causing the problem >>>>

What is this line supposed to accomplish?

[Tondunard]

i guess i didn't expose my problem clearly as i can see

yes i want to transmit the whole line (si i need to store it in a variable in some way)


to tell the truth, i have this radio that has GPS capabilities but it has to be "polled" so as far i can say , it does not transmit every second (the radio that is),.
so the radio transmit it's position every time i "poll" it.

after that i need to take that information and resend it to a gps software every second (to simulate a directly connected GPS)

plus i need to check for incoming data while this second by second transmit to the pc is done.( next strip of NMEA)

i guess it's better explained that way

thanks for the concern, looks like a real good place to learn picbasic

[skimask]

i guess i didn't expose my problem clearly as i can see
yes i want to transmit the whole line (si i need to store it in a variable in some way)
to tell the truth, i have this radio that has GPS capabilities but it has to be "polled" so as far i can say , it does not transmit every second (the radio that is),.
so the radio transmit it's position every time i "poll" it.
after that i need to take that information and resend it to a gps software every second (to simulate a directly connected GPS)
plus i need to check for incoming data while this second by second transmit to the pc is done.( next strip of NMEA)
i guess it's better explained that way
thanks for the concern, looks like a real good place to learn picbasic

The holy GREEN MANUAL describes how to handle strings using HSERIN/HSEROUT quite well.
And you might even find a use for WAIT in there too.

[Tondunard]

The holy GREEN MANUAL describes how to handle strings using HSERIN/HSEROUT quite well.
And you might even find a use for WAIT in there too.

i'll check again (guess i haven't looked too well

Still searching.....

[b1arrk5]

As you already have the hardware uart connected to the GPS unit, I'll ask how do you have the PC connected? 4800 baud is standard for a GPS unit, so you're good there. Skimask has correctly suggested that you will find that PicBasic's Hserin command does let you accept an entire string at once, instead of reading in a single character at a time and building a string like you are trying to do. You'll have to declare an array variable big enough to accept all of the characters in your string.
I would use an interrupt to capture the incoming string from the GPS unit, and then either DEBUG or SEROUT to send the string out to the PC. There are a few serial interrupt example programs on the MicroEngineering Labs website, and there are a lot of examples on this forum, and debug and serout or serout2 are explained well in the manual.

Jerry.