SIM548C Tracking System Project

[thegood]

Hello everybody,

I am using SIM548C GSM/Gps combo module for an educational project. I have the module and evaluation board. However, I am stuck with some problems.

Firstly, I don't know how to send AT commands via SMS to the device and how to get responses to the SMS sender. Does anyone know how to do this?

Secondly, the guide says when I connected GPS_COMA via hyperterminal, I should see GPS info on the Hyperterminal window. But it doesn't work. So, I tried TeraTerm istead of Hyperterminal and seen meaningless messages. May anyone help me how to adjust the gps part of the module?

Any help will be much appreciated. I will be very grateful. Thank you in advance.

Best wishes,
Osman

 

[ckshivaram]

if the message is continuous and meaning less then you baud rate is different. check GPS module baud rate and set the same parameters in hyperterminal or tera term.

what is the baud rate of gps

 

[thegood]

thank you very much for your reply!!! in the evb_user_guide, it is written that the default baud rate of the SIM548C is 115200. But I don't understand why the AT commands for GPS can't be send to the device. do you have an idea what the reason could be? and do you know how to send AT commands to the device via sms? these questions are remaing.

Best wishes,
Osman

 

[ckshivaram]

AT commands are for GSM not for GPS, dear friend....

---------- Post added at 23:34 ---------- Previous post was at 23:33 ----------

set baud rate as 115200- 8 data bits -1stop bit - parity none ... see if you get the gps output

 

[thegood]

I will try it, thanks. I am sending an attachment which includes the AT commands for gps part. though they are sent to the gsm part. maybe I might be missing something.

 

[ckshivaram]

no you are correct. this are just initialisation and setting commands,, not required everytime.... only if GPS sends 00000000 as data, if you dont use it for long long time then these are used. earlier a small GUI(graphical user interface window) was provided to send these commands.. not in the form of AT commands....

now it is changed...

 

[thegood]

How can I find that interface? thought it might be helpful

 

[ckshivaram]

first get it in tera term or hyperterminal my friend.. GUI does not make much difference..... please tell me your result.. keen to listen to your answer

 

[thegood]

Sorry for the delay. I tried 115200 but it didn't work. However, what you prosposed to me maked sense and I tried other baud rates and got the results at 4800!!! thank you very much for your help.

But I cant send those AT commands for GPS still. TA just returns to ERROR. Maybe that guı would help... or any other suggestion...

 

[ckshivaram]

i dont think there is AT for GPS... yes most of the GPS default baud rate is 4800 only , i forgot to tell you.....

but GUI was useful for only GPS i dont know if it is compatible with SIMCOMM.. anyhow i will post it... but way long back i think i had posted it here. meanwhile you search for it

 

[ckshivaram]

check this GUI.. but not sure if it supports SIMCOM

 

[hai0308bk]

To ckshivaram: thanks for your GUI, it is very useful for me, however, i have a big problem, i hope you will show me right way to do, please.
When i connect GPS part (sim548c module) with terminal, it send messages without latitude and longitude . wait a long time but nothing data.
for example:
$GPGGA,002605.059,,,,,0,00,,,M,0.0,M,,0000*5B

$GPGSA,A,1,,,,,,,,,,,,,,,*1E

$GPRMC,002605.059,V,,,,,,,010407,,,N*42

plzzz show me how to do.

 

[ckshivaram]

In one of my post i had recently explained about the reason for getting the wrong data or no data from GPS...

I will explain again.....

Ig your GPS module is not powered ON for many days say 4 to 5 days or more than that, it enter cold start mode... In this mode it do not get any data from GPS satellites, until the clock gets synchronized with the satellite clock... it may take few minutes or hours depending on the precision of the GPS module you have... Some need to be powered ON for about 4 to 6 hours or some in worst case need to be powered on for 12 to 14 hours before GPS gets correct data from satellite...

This is a normal procedure in all the GPS receivers... No need to Panic or doubt about your module...

The new or correct data will not appear till the entire flash of GPS is overwritten with corect data...

For that purpose we do something called warm start or hot start to gps module... Warm start forces the GPS to take the last received and stored good value and try to synchronise with satellite... HOT start forces GPS to take the reading of top of stack and syn very quickly with few minutes of power ON... That open of triggering GPS with cold, warm ,, HOt start is available in the GUI i provided, ( But cant remember excatly where it is as its about 8 years i used it).

please let me know if anymore clarification is required....

 

[hai0308bk]

Thank you for reply, i will do as you show

 

[hai0308bk]

it's just done well when i moved GPS antenna to new open sky. My lab is not open area to test. However, when get lat/longitude data, i see they are not good. They change every second. GPS firmware in the module does not support AGPS.
So i add 1000 times all lat/longitude data i receive, then arithmetic mean. Is it right? please.

 

[ckshivaram]

I am afraid , Not excatly correct, and wont get accurate results by doing this...

 

[hai0308bk]

So what should i do in this case to improve results ? please

 

[ckshivaram]

there are 2 methods.. But costly ideas

1. go for GPS with high resolution.
2. design a antenna yourself with the required gain..

both seems to be not feasible... but that what you can do...

 

[mrsalesi]

Hi all.

If any body have PCB of "sim 548c" or proteus schematic plz help me .
I try to drawing a PCB to connect sim548c on bred board but it have some problems that i cant do it .

So are there any body that have any PCB file or Proteus file ?