Problem with GPS output at 4800 and 115200 baud rate

[devil6600]

for some reason gps module is returning partial garbage output, this is the output at 115200 baud:

üÑüÑÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿüÑüÑüÑ€üÑüÑüÑüÑ	H	È‚jR’¢âÑüÑüÑüÑüÑüÑÿÿŽ(\üÑüÑ4üÑüÑ1,,,,,,,,,,,,,,,*,E1

üÑüÑ04.19109E,0,0,,0050.4,.943M,0,0.,0,M*,56

üÑüÑÿÛ€ üÑüÑdüÑüÑüÑüÑÿÿýÿüÑüÑüÑdüÑüÑ,0,,*,97

üÑüÑÿÿ,0,M*,F6

üÑüÑùüÑüÑüÑüÑ.400,0,V22231.26,6,N1104.19109E,,,,,,,*N07

üÑüѼÄüÑüÑüÑüÑüÑüÑ,0,V22231.26,6,N1104.19109E,,,,,,,*N77

üÑüÑüÑüÑüÑüÑëŽüÑC7

üÑüÑ€26,6,N1104.19109E,0,0,,0050.4,.943M,0,0.,0,M*,46

üÑüÑüÑüÑüÑüÑ4üÑüÑüÑ4üÑüÑüÑüÑùüÑüÑüÑG$RPCM0,0011.500,0,V22231.26,6,N1104.19109E,,,,,,,*N57

üÑ,0,M*,26

üÑüÑùüÑüÑüÑüÑ4üÑüÑ,,,,,,,,*,E1

üÑ€düÑüÑùüÑüÑüÑüÑÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ4üÑ09E,,,,,,,*N27

üÑüÑG$GPAG0,0031.200,022231.26,6,N1104.19109E,0,0,,0050.4,.943M,0,0.,0,M*,46

üÑüÑ*R'T,.){Ð+Ê,ېÁüÑùüÑ€üÑ

üÑüÑ4üÑüяªüÑùüÑüÑ€üÑ€üÑ4üÑüÑüÑ€üÑÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿüÑ””€ üÑüÑüÑ4üÑüÑüÑ4,.943M,0,0.,0,M*,46

üÑüÑüÑüÑüÑ€üÑüÑ,0,V22231.26,6,N1104.19109E,,,,,,,*N37

üÑüÑüÑùüÑùüÑüÑüÑ4üÑ

üÑüÑÿÿÿ,022231.26,6,N1104.19109E,0,0,,0050.4,.943M,0,0.,0,M*,76

üÑüÑüÑüÑüÑ4üÑüÑ,,*N57

üÑüÑ$üÑüÑüÑüÑüÑ4üÑüÑ€E,0,0,,0050.4,.943M,0,0.,0,M*,16

üÑÿüÑùüÑ€ üÑÿÿŽ(\üÑüÑÿÿÿÿÿÿÿÿ4üÑüÑüÑüÑ04.19109E,0,0,,0050.4,.943M,0,0.,0,M*,66

üÑüÑùüÑùüÑüÑüÑ,,,,*,E1

üÑüÑ}ýüÑùüÑ)o&›,Ñ)¼H#+î-pINüÑüÑüÑ

üÑ,0,V22231.26,6,N1104.19109E,,,,,,,*N17

üÑ

üÑüÑüÑüÑüÑüÑüÑüÑÿÿüÑüÑüѨŽ)8*¥üÑdüÑüÑ€üÑÖÏ¿üÑCM0,4940.796,4,V22231.26,6,N1104.19109E,,,,,,,*N57

üÑÓõüÑüÑüÑüÑüÑ1,,4541,61,,301,,491,14*
AüÑ€üÑüÑ\(^üÑV}üÑüÑüÑüÑúøüÑüÑüÑ€ üÑ€üÑüÑ(üÑüÑüÑ4901.666,9,V22231.26,6,N1104.19109E,,,1,0314,1,,*N57

04,,320,,413,82,,2111,96*,C7

G$GPVS3,3,1,,1615,,532,81,,4541,61,,301,,491,14*
AüÑüÑüÑüÑ…_xÔÿýüÑùüÑÿþŽ>feüÑüÑüÑ.456,822231.26,6,N1104.19109E,0,0,,0050.4,.943M,0,0.,0,M*,66

9süÑ'òØ®÷Çêã¹üÑüÑÿÿŽ(\ùüÑO4üÑüÑüÑüÑüÑüÑ1104.19109E,0,0,,0050.4,.943M,0,0.,0,M*,06

üÑüÑüÑ.346,622231.26,6,N1104.19109E,0,0,,0050.4,.943M,0,0.,0,M*,D6

üÑY)ŽÿÚüÑüÑýÎxŽüÑTÔ¢îüÑüÑ,,*NC7

üÑüÑ,510,53,,0372,87*,D7

G$GPVS3,2,1,,1921,,850,72,,5600,04,,320,,413,82,,2111,96*,C7

G$GPVS3,3,1,,1615,,632,81,,4541,61,,301,,491,14*
9üÑüÑ,0,M*,96

üÑüÑ»x}âüÑüÑ€üÑüÑüÑé½WüÑüÑüÑ

G$GPVS3,3,1,,1221,,161,91,,6652,83,,414,,511,64*
8üÑ€üÑüÑüÑüÑüÑ~ùÿþüч€üÑN¾k‚ÿÿšÊoôüÑVS3,1,1,,1602,,371,9233,,2932,38,,134,,510,53,,0372,87*,D7

G$GPVS3,2,1,,1921,,850,72,,5600,04,,320,,413,92,,2111,96*,D7

G$GPVS3,3,1,,1615,,632,81,,4541,61,,301,,491,14*
9üÑüÑüÑüÑüÑüÑÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿüÑüÑüÑüÑüÑüÑ2,,5600,04,,320,,413,92,,2111,96*,C7

G$GPVS3,3,1,,1615,,632,81,,4541,61,,301,,491,14*
9üÑÑÁüÑüÑüÑ
üÑüÑüÑféÿÿµóX—üÑ{@HÔüÑÿ.,4541,61,,301,,491,14*
9üÑüÑ,,,,,,,,*,E1

4,,510,63,,0372,08*,97

G$GPVS3,2,1,,1921,,850,62,,5600,04,,320,,413,92,,2111,96*,C7

G$GPVS3,3,1,,1615,,632,81,,4541,61,,301,,491,14*
9üÑüÑ?üÑüÑY¢ƒüÑüÑüшüÑhõÿÿaXrüÑÀüÑ,0,M*,96

üÑüÑV¨ÿðüÑüÑFªÿÿüÑ
üÑüÑüÑ,1615,,632,81,,4541,61,,301,,491,14*
9üÑüÑüÑ€
üÑ,0,M*,96

üÑüÑ4üÑüÑüÑ

i am using max232 for pc interfacing. i have already checked the datasheet for baud rate and other parameters. and as per datasheet by default module works baud is 4800 and i should get proper output at 4800 baud, but i am getting garbage string and only at 115200 i get partial output, if some one can help me i would really appreciate it.
thanks

this is the output at 4800 baud

   *# 0  *	( " pD!*   * @ ÄapFj *Å88œ"Îá8bP*ÿ0     €   PX      
* @ "$(¾pŒ\F0X¸"T0Rä 3b è €        D_"  * ˆ8(¬¶œ)Ð@A@0ÿ!          @ Äap`xPbQ*8Y0AÄú¨       `0  à$   `r $0       „  ˆ8(`òŠ0aVbì<U(ðàÿ¨         ¢8  p@ ù    T   $ $"$ 
  A      *@H       `@   `  |$  0 Œ $ @ 0 " $ ÜA0Xº"pˆ  ƒ`*(è
   
! Æ   A D¨ 
a°Ib°\¨B"8pˆ£A"ÿ 
        \@     Tþ

 

[hussain_kiet]

Re: help with GPS output

make sure the connections are ok. No loose connections and check for the datasheet of GPS for baud rate and other parameters settings...

 

[manikandan10]

Re: help with GPS output

hi are u interfacing with controller are directly connected to PC via max 232. if controller, which controller are you using ?

 

[devil6600]

Re: help with GPS output

thanks for your response
hussain_kiet, i have triple checked each and every connection, check datasheet. as per datasheet i should get output at 4800 baud (default) but getting garbage string. checked max232 and power supply, both of them are good.

manikandan10, by controller what do you mean, gps module itself?

 

[hussain_kiet]

Re: help with GPS output

for testing your circuit you can do is remove the GPS and short the receive and transmit pin of the max232 TTL end and send some characters through hyper terminal and check if they are Looped back...
note: you might not be using receive line at the GPS end but connect it and check loop back.
if loop back works fine then the problem might be in GPS or the rs232 settings (baud rate, data bits, parity, start stop bits etc...)

also your max 232 circuit is ok..? I mean the capacitor values.

 

[horace1]

Re: help with GPS output

as you are getting some characters correct it looks as though the baud rate at 9600 is correct. As you are getting characters printed from the extended character set it looks as though bit 7 is being set sometimes. Check the number of data bits and parity settings. also try masking out bit 7 ?

 

[devil6600]

Re: help with GPS output

as you are getting some characters correct it looks as though the baud rate at 9600 is correct. As you are getting characters printed from the extended character set it looks as though bit 7 is being set sometimes. Check the number of data bits and parity settings. also try masking out bit 7 ?

there is no problem with max232 or power supply, both of these are working with my other setup.

horace1, how to mask bit 7?? i am using hyperterminal.
i have checked datasheet, it states data format to be 4800 baud rate(default), no parity, eight bit and one stop bit. LSB sent first.

generally LSB is sent first or MSB?

 

[hussain_kiet]

Re: help with GPS output

have you tried all the baud rates between 4800 & 115200...?

 

[horace1]

Re: help with GPS output

LSB is send first in RS232 serial communications

looking at some of your data such as
RPCM0,0011.500,0,V22231.26,6,N1104.19109E,,,,,,,*N57

and comparing it with a NMEA sentence
$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47

you appear to be completly missing some characters and corrupting others
1. do you have hyperterm set to two stop bits and it is sending one?
2. are you using a very slow old machine, what operating system?

you could try teraterm pro as a terminal emulator
Tera Term Open Source Project

 

[devil6600]

Re: help with GPS output

LSB is send first in RS232 serial communications

looking at some of your data such as
RPCM0,0011.500,0,V22231.26,6,N1104.19109E,,,,,,,*N57

and comparing it with a NMEA sentence
$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47

you appear to be completly missing some characters and corrupting others
1. do you have hyperterm set to two stop bits and it is sending one?
2. are you using a very slow old machine, what operating system?

you could try teraterm pro as a terminal emulator
Tera Term Open Source Project

i have tried teraterm, still getting same response
is it possible that the module itself have some manufacturing defect? for me its hard to believe that module have manufacturing defect since its returning partial data and as far as max232 interfacing is concern its working for all the baud rates with my other uC. then what i am doing wrong?!?!?

 

[horace1]

Re: help with GPS output

have you looked at the signals with an oscilloscope? are the voltage levels correct, no noise, correct grounds, etc?

 

[hugo00]

Re: help with GPS output

i have tried teraterm, still getting same response
is it possible that the module itself have some manufacturing defect? for me its hard to believe that module have manufacturing defect since its returning partial data and as far as max232 interfacing is concern its working for all the baud rates with my other uC. then what i am doing wrong?!?!?

Hi devil,
Did you try to reset the unit (factory reset? Try to send the unit command: $PGRMI ,7*HH or PGRMC command) you can try **broken link removed**, NMEA data, NMEA 0183 sentences (nmea), there is lot of NMEA sentences and explanation, I believe if you reset the receiver for factory reset than should work as data sheet suggesting.lot of data is in included pdf’s
Perhaps best will be – d/l – software from **broken link removed** (the unit should use the SiRF chip and get all info from unit even resetting manually you can use the
$PSRF101 command) reference you can find in showfile.PDF

:razz: That can be fun.
Hugo

 

[bigdogguru]

What GPS module are you using, the model number? Is it a 3.3v device?

---------- Post added at 08:18 ---------- Previous post was at 08:08 ----------

If it's a newer model GPS module most require 3.3v. If this is the case you shouldn't be using MAX232 (5V only), try a MAX3232.