Hey all,
I am doing a project on Vehicle Tracking System using GPS and GSM Modem.The 2 devices aforementioned communicates with 8051uC. But since there is only 1 UART in 8051 i have to use a analog multiplexer i.e CD 4062. I want to know how to interface it with GPS, GSM, and 8051.
Also it would be grateful if anyone could tell me how to parse output of GPS and how initialize a GPS receiver to that it starts giving me the GPRMC
Oh no, here we go again!
Since a fundamental part of your project is communicating with two serial devices, why not just use a processor with two UARTs?!
Plenty exist: http://www.keil.com/dd/search_parm.asp
"i have to use a analog multiplexer"
Even if you do decide to make life difficult for yourself by using a multiplexer, Why does it have to be analogue?
This school assignment comes up regularly - use the 'Search' facility on this site to find previous discussions here, and Google (or other search engine) to find them elsewhere...
Use a chip with two serial ports. Only then will you be able to receive data from the GSM at the same time that your GPS emits data. Using a chip with a single UART when multiple UARTS are needed is so 1980.
See the documentation for your specific GPS to figure out what init strings you need to send to it.
Decoding a GPRMC string should be a quite trivial operation. The checksum is trivial. Splitting it into individual parameter fields is trivial. Converting the individual fields is trivial. So really no need to post a lot of source that has been written with possibly different requirements in mind.
I would be using a SIM300 GSM modem and a GPS receiver with SiRFstarIIe-chip-set.......Now can I have the sample codes.please Also I think irrespective of what GPS receiver u choose the output is just the same. All I want from the GPS is the RMC data
Also if u could suggest me a better GPS which highly accurate and also affordable at the same time I would be grateful.
No one (who actually knows what they are doing) is going to give you the code that you are looking for.
The point of this assignment, and school in general, is to get YOU to learn how to do things for YOURSELF.
You are correct that most GPS modules output a NMEA serial data stream, but YOU have to learn how to parse and handle that data.
May of the people here are happy to help if you get stuck on a problem and are able to clearly articulate that problem and what you have done to try and fix it. None of us are interested in doing your homework for you.
ND
See you are getting me all wrong. I wasn't even expecting you to do my homework and mind you It would be me that would be doing it all . I was just seeking info on how to parse the data because GPS' output would be a long string and and the data registers in 8051 would all be 8 bits so how would i manage saving such a long String. Just provide me with the logic and i'll definitely will reply you when I get the whole code written.. By the way thanks but pls be there when i'm stuck somewhere PLSSSS
So. Now you asked a specific question.
One possible route (and the possibilities are legio):
char my_nmea_string[NMEA_BUF_SIZE]; if (!strncmp(my_nmea_string,"$GPRMC",6)) { // almost there. just continue to gnaw characters // one at a time until reaching end of string ... }
Or you can have the interrupt code (normally not so good idea but depends on what interrupt load you have, and timing requirements) have a state machine and process each receievd character based on current state. If currently waiting for a number you just check if character is field separator or part of the number.
Whatever you do, you just have to process the received data character-by-character. Optionally after having collected a full text line in a buffer (and possibly verified the checksum). Just remember that the line break and the $ can be very handy for synchronizing if you start listening in the middle of a line.
About processors with multiple UART - check parametric search on this web site. Finds a lot of chips with multiple UART:
And you are correct that the parsing of a $GPRMC string looks similar even with different GPS - I already mentioned that earlier. So your general skills at programming should be able to solve the problem. Most C solutions that works on a PC would work on a 8051 too for the specific case of handling an $GPRMC string. And it's quite easy to process the $GPRMC string in assembler to.
A creative developer sees possibilities. What possibilities have you identified?
See you are getting me all wrong.
I don't think we are. We're getting that you consistently ignore all advice you've been given, keep asking the same questions over and over instead, and insist on the answers being given in one form, and one form only: pre-fabricated source code.
It would be me that would be doing it all
No, it wouldn't. It would be you piecing other people's work together at best.
I was just seeking info
No, you weren't. You were expressly seeking for source code.
By the way thanks but pls be there when i'm stuck somewhere
You're royally stuck already, and people have already tried to help you with that by pointing out the problem to you --- only to be summarily ignored.
See actually i am new to serial communication Ive been working with uC's for about a year or so but never did anything related to serial communication. Please try to understand. The reason why i was asking for the code was because i would have got an idea by that way.It would have alright ifyou could have just replied me not with the GPS' output but any random program related to serial communication. I think you misunderstood me and I misunderstood you. Lets close that chapter. And mark a new beginning
5 minutes looking around on this site - or looking around on your computer - should give you a good starting ground for serial communication.
Processing $GPRMC strings doesn't have anything to do with serial communication. You could just as well have received the data from a file on a memory card or have the strings hard-coded in the source code.
When writing software, you partition your problem into smaller pieces until you have pieces small enough for you to handle. Receiving data, and decoding data is definitely two separate pieces. And processing NMEA strings is also possible to see as multiple tasks. - Locating record separators (i.e. individual text lines) - Computing checksum - Splitting line into individual fields - Decoding the contents of the different fields - Using the decoded data in an application-specific way.
Yes - you start by following the links you've already been given, and doing a bit of study and research.
"Ive been working with uC's for about a year or so but never did anything related to serial communication"
I find that quite amazing - to have gone a whole year and done nothing with serial comms!
Really, serial comms is a very, very, very common part of microcontroller/embedded systems!
After "blinky", a "hello, world" program on the UART must be one of most developer's first programs.
You really should have no problem at all finding plenty of examples of it!
Start on this very website: http://www.keil.com/download/ http://www.keil.com/books
and take it from there...
Ive been working with uC's for about a year doing what?
Erik
Putting in fresh batteries and then pressing the remote control buttons? Or plugging in the headphones and then activated the MP3 player.
As Andy notes, serial comms is hard to avoid. Even products that doesn't need a serial port normally makes use of one just to be able to be programmed or for emitting debug information or similar.
See I've been doing projects like Temperature Sensor and Regulator, Security Lock Code, Data Acquisition System and projects like these so i have never been Serial Communication consequently not good knowledge of it but i do have some basic knowledge.. I think you all are trying to pull my leg, you've been insulting me Isn't it?
I gave you a link to the Device Database Parametric Search - all you had to do was click it, and you could easily have found chips with 2 UARTs and all your other requirements.
Did you do that? No - you just asked people to tell you chips.
If you want people to believe that you are actually interested in doing some work yourself, then you need to demonstrate it!
Look, buddy, if you came over here to get some "respect" - you are invited to leave right NOW. People here are interested in helping you if you actually help them to help you! Step 1: Follow their advise!
See I've been doing projects like Temperature Sensor and Regulator, Security Lock Code, Data Acquisition System doing? copying from the net? actually designing hardware? actually designing software?
If you want help show where you are, "I have" NOT "I need".
e.g. a code snippet can show better than a thousand words what you (do not) know.
Giving you "sample code" will just lead to frustration on both sides.
Surely you cannot accuse of me copying my projects from net, It's me who knows how much dedicated efforts and sleepless night i spend for my projects.
It seems that the only thing which made you all lunatic at me was me asking you for the sample codes and i also gave u a reason for that.
But nevertheless, can't we now just get back to the basics. I wasn't here for a duel with you all. Vehicle Tracking System is my BTech project and is dearly close to me. All I want is full support from your side. Because I know the deeper i go into the project, the more tedious it would be going to be. All you tech savvy people with great application oriented knowledge Pls be with me then.
No, it's the way that you totally ignored all suggestions, and showed no evidence of having done any work at all of your own!
"can't we now just get back to the basics"
OK - These are the things that you need to do now:
1. You need to use the database search to find some potential candidate processors that meet your needs (including the 2 UARTs). If you then need some help selecting from the candidates, ask specific questions (but be sure that you have studied the datasheets first).
2. You need to do some research into how to use the serial port on your chosen processor. As already noted, it really is an extremely common task - and, thus, there are plenty of tutorials, examples, etc readily available all over the web.
3. You need to do some research into handling the output from a GPS receiver. As already noted, NMEA is a long-established and widely-used format - so, again, there are plenty of tutorials, examples, etc readily available on the web.
4. You need to do some research into controlling modems using AT Commands. As already noted, this is a long-established and widely-used format - so, again, there are plenty of tutorials, examples, etc readily available on the web.
Note that this is the standard way to start any project - called the research phase - that's why it is important that you learn to do it yourself!
To do all this you will need to take advantage of resource such as:
* Internet search engines - such as Google;
* Manufacturer's websites - including this one - where you will find technical documentation, datasheets, application notes, reference designs, examples, etc, etc. Be sure to make use of the 'Search' facility on these websites...
* Your college library - where you will find books on programming, etc
"I wasn't here for a duel with you all"
So stop fighting, and start working! Show some evidence that you have done some work on this!
Here are some links to get you started: www.8052.com/.../160143 http://www.keil.com/download/ http://www.keil.com/books http://www.8052.com/faqs www.keil.com/.../search.asp
Your project requires 2 UARTs for its basic operation - so these will be dedicated to the GPS and GSM.
You also need to think about how you will monitor and debug your project. A "spare" UART can be extremely useful - some would even say invaluable - for this.
So think carefully before limiting yourself with only 2 UARTs - there are plenty of chips with 3 (and more!) UARTs...
You already have the link to identify such chips...
Thank you, I went through the link to identify the chips. As I am keen on working with 8051 family. I came across AT 89C51RE2. It had features which suites me well.There is no MCU with 3 UARTS(in 8051 family). Also 89C51RE2 doesnt have a feature called as " ON CHIP DEBUG" ....What exactly is on chip debug. What is the difference between ISP(In System Programming) and IAC(In Application Programming)
In-system programming means that you can download new firmware to the chip without desoldering the chip.
You sometimes have dedicated pins, and sometimes have pins with multiple function. You might for example have a SPI interface that is "normal" SPI when the processor is running, but is a programming interface when the reset signal is active.
In-application programming means that your own application can directly or indirectly reprogram some parts of the flash contents. You might for example be able to write new code to XDATA and this is aliased with flash memory.
By the way - why do you say no 8051 chip exists with 3 UART? What about Dallas DS80C400?
Yes I know about DS80C400 having 3 UARTS but in the previous thread forgot to metion 3 UARTS + ISP. NO MCU with 3 UARTS + ISP.
Also Pls help me with what is called as ON CHIP DEBUG
Please note the difference between a "thread" and a "post":
A "post" is a single messge by a single author;
A "thread" is a collection of related posts - usually from different authors.
This is pretty well self descriptive!
It means that the chip has debug hardware built-in.
This means that a debugger can directly access the "internals" of the chip - CPU registers, memory, etc - without needing any special software running on the chip.
Without on-chip debug, the only way to gain such access was to remove the chip and physically replace it with an In-Circuit Emulator - or "ICE" for short. Hence on-chip debug is often referred to (not entirely accurately) as "on-chip ICE".
Why?
You say that you can't find any 8051-family chips that meet your requirements; so why are you "keen" to use a family that doesn't meet your needs - especially when other families so clearly do!
OR, do you actually mean that you already know the 8051 architecture, and have the tools, and don't (think you) have time to learn a new one? That could be a good reason to stick with 8051, but you really need to be clear about the pros and cons - and not just make vague statements like, "I am keen on..."
Correctly said that I actually mean that you already know the 8051 architecture, and have the tools hence i am keen on working with 8051 family.
Also Pls help me with the selection of GPS. What parameters should i look for in my GPS receiver. One of my friends told me that look for GPS with 20 or more channels What does this statement exactly mean? What all parameters should i look for before buying a GPS receiver
More channels are obviously nice, but maybe even nicer: - a receiver that supports multiple satellite systems (GLONASS or maybe upcomming Galileo, ...) - a receiver that very quickly locks on. - a receiver that allows use of a super-cap or battery to keep information (last position, ephemeris) even when you turn off your equipment - this allows for faster tracking when you turn it on - a receiver with high sensitivity - a receiver with extended precision, supporting WAAS, EGNOS or similar. - a receiver that can emit multiple positions every second, to reduce problems with lag. - a receiver that supports the specific NMEA strings you want - or maybe you prefer SiRF Binary? - direct support for powering an active antenna. - low power consumption. - "correct" supply voltage. - suitable form factor. - ...
There are a huge number of parameters to think about when selecting a GPS. Number of channels it can track is just a single parameter.
What do we mean by Extended RAM (XRAM).It was stated in the AT89C51RE2 data sheet that it has On-chip 8192 bytes Expanded RAM (XRAM) – Software Selectable Size (0, 256, 512, 768, 1024, 1792, 2048, 4096, 8192 bytes)
When i tried Googling it the info was reagrding X-fi and XRAM used in games. I couldn't make out the difference between XRAM and other normally used RAMs
Pls Help
I thought you said you were familiar with the 8051 architecture?!
XRAM, in the context of an 8051, is memory accessed by the MOVX instruction.
It was originally called 'X' for eXternal - because it was physically external to the 8051 chip.
Nowadays, most 8051-derivatives have at least some MOVX-addresses memory on-chip - so some people (including some chipmakers) fudge the issue by trying to give it different names.
As far as the CPU - and, therefore, your code - is concerned, it is all just MOVX-addressed memory; it is irrelevant whether it is physically on or off the chip.
What do we mean by Extended RAM (XRAM).
The fact that you ask this puts the lie to your earlier claim that you were keen on using an 8051 because you "knew the architecture". You clearly don't.
"The fact that you ask this puts the lie to your earlier claim that you were keen on using an 8051 because you "knew the architecture". You clearly don't."
The reason why I asked you this because if it is XRAM it was external to the chip.But now since the datasheets say"ON CHIP XRAM" I was a little bit confused if its ON CHIP why is it "X".
Pls consider me worthy of something. Sometimes the question may sound too foolish but it is of great importance to someone
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