Car tracker using GPS and GSM with one hardware USART chip

[princejude]

[princejude]

[princejude]

[princejude]

...sorry for multiple posting, my internet service is very slow now

[ezflyr]

Hi princejude,

The reason I said you are hopeless, and that you don't even seem to be able to help yourself, is that even now you refuse to tell use where you got the modem, or to post a link to the vendor. You were asked to do that multiple times in this thread, and so far you've ignored that request.

If I bought a piece of hardware that was not supplied with any documentation, you can bet that the first thing I'd do is contact the vendor and obtain it. If no documentation was available, I'd return the product.

As I said, you can learn a lot about good engineering practices here on the forum, but frankly that requires a "heads up attitude" which I've yet to see from you. If you had the documentation for your modem, or if you had a different modem that is well documented (like the one I mentioned on page 1), this thread would have wrapped up in be 3 or 4 posts, rather than dragging out for 3+ pages.

Honestly, I'm not trying to "pile on" you here, but rather to encourage you to take a different, more productive approach to problem solving. I hope you get your GSM project working, as they are pretty cool when they do work!

John

[Ttelmah]

It is also worth making the point that being Chinese, _doesn't_ imply data is not available. Most Chinese manufacturers, both of electronics kit, and mechanical stuff, are trying to sell into World markets, and know how vital data is. I've had motors from China, with superb .pdf mechanical drawings, and electronics with quite competent data sheets. Sometimes they are a little 'odd' with sections where translation has obviously be done by somebody probably using software, rather than actually being able to talk English, with some quite 'exotic' Chinglish, but technical tables are the same whatever the language.

Best Wishes

[princejude]

Ok, I will try to get the documentation or the link of the manufacturer.

[ckielstra]

I'm starting to loose my patience as well because you still don't post the link to your supplier. Even when you don't want to post it, then just say so and be done with it. Now it looks like you don't take us seriously and then I'm going to waste my time on nicer subjects (girlfriend, tv, sleeping, etc.).

Just before you damage your modem a few remarks:
- I told you the modem is running at a low voltage, according to this Hardware Interface Description the logic signals on the ZIF connector are 2.65V. Even when the interface board is powered by 5V the modem module has an internal power supply to reduce the voltage. A direct connection between the logic header on the PCB and your 5V PIC could destroy one or both devices. You need voltage translation logic, or even better have the PIC run at the same low voltage.
- Even with the right connections and voltages it is good practice to place 100 Ohm resistors in series with each data line.
- Check my remarks on DTE and DCE device types in this thread. On a modem you often need a straight cable; Tx PIC to Tx Modem and vice versa for Rx. See table 4.8 of the linked datasheet for which pins are input and output.

Even without datasheets the above mentioned issues can easily be checked with a voltage meter and should have been done so by you. Just get your voltage meter out right now and double check my suggestions. Never believe anything, check for yourself.

I leave it to you to find the TC35 AT Command manual.

[princejude]

Hello,
The modem was sourced through www.taobao.com

[princejude]

Thank you all for all your wonderful comments, I will try all your suggestions and post the results later.