Open GPS Tracker user forum

On the ATTINY84 and ATMEGA88 these new features are working:
SETIO - set the direction and default state of digital I/O pins (retained in EEPROM)
OUTPUT - set the state of digital output pins
OUTPULSE - momentarily change the state of output pins - used to set latching relays
INPUT - read the digital state of input pins
ALERT - send a text message when a selected pin changes state. This is interrupt driven and will catch very short changes.
Any line can be set to input with pull-up, so a switch closure to ground generates an alert.
MEASURE - read the analog value (0 - 3.3 volts = 0 - 1023) of analog inputs. Also reads the TINY84’s rather approximate temperature sensor.

For the ATTINY84, lines A3-A7 are the I/O and can be digital outputs, digital inputs, or analog inputs.
For the ATMEGA88, lines B0-B7 are digital I/O and lines C0-C5 are analog inputs.
On the ATMEGA88, the LED is on D3-D4 and GPS power is on D5.

Todo:
Test the other phones (including one which is on the way.)
More regression testing.

The build 0.18 code assembles to the same binary as build 0.17A if the new features are turned off.
There are define options at the top of the file to enable and disable features.

Who sells mercury switches (or equivalent) nowadays? One simple and handy use for build 0.18 will be to connect a mercury switch to an input line, and enable alerting. The unit can then be hung on a doorknob, put in a briefcase, etc. and if that object moves you will know about it anywhere in the world. Even without a GPS module, this makes a cheap and handy long-distance alarm.

I am working on build 0.18 now.

Planned features:

• Runs on the ATMEGA88 or ATTINY84 processor.
• Support for more phones and GSM modules.
• Ability to remotely turn on and off output lines on the MCU.
• Ability to sense input lines on the MCU.
• Alarm function to send a text message when an input changes.
• Measurement of analog inputs, including tracker battery status.

Current status:

• Generates identical code to 0.17A when assembled with same options.
• Boots and responds to text messages on the ATMEGA88.
• Code for other phones is copied in but not tested.
• Basic input/output (set and read bits) works.

I need to finish building my ATMEGA88 development board. So far it has only a processor, decoupling capacitor, programming plug, status LED, and connections for the phone. I would like to test on an ATMEGA168, but right now I do not have one.

The T720 does not seem to have the AT+CNMI command. All forms of it return error. Without AT+CNMI how do I find out if there is a new message pending? Does anyone know of another way?

One option is to poll every couple of minutes, but that has a linear trade-off between frequency of response and battery drain. Is there any other command that will produce an asynchronous notification of new messages coming in?

The site now has phpBB installed. That provides proper threaded discussion, unlike Wordpress.

http://www.opengpstracker.org/phpBB3/

So far there is a general forum, guests can browse, and registered users can post. Please suggest any additional forums I should create. If you are working on a project/port and want to own a forum, please let me know.

My Motorola T720 finally showed up, and looks like it should work. I tested it with the computer but not with the tracker yet.

The cable requires power to communicate with the phone, so there must be a level converter in there. With the right connector the tracker should connect right to the phone. I suspect the USB cable has the right wires, and a cheap one could be cut up.

All the commands work except I have not found out how to turn on unsolicited notification of new messages yet. Does anyone know? The AT+CNMI does not work.

I am on vacation until May 27 and will test afterward. Sometime in early June the next version should be out with wider phone support.

Until then, the C168i is $14.95 at Target.

Build 0.17A is posted, fixing a bug where manual locates would fail while in tracking mode. The memory used to store locate data was being overwritten during the phone poll. This fix just locates again before sending.

May 10th is the last day to get a free phone at Best Buy.

Here are two neat trackers that were recently built:

Wayne sent me this picture - he programmed a milling machine to make a two-sided circuit board. This is the smallest and neatest build I have seen, and much nicer than my own.

This one has an additional 7805 regulator, Schottky diodes, and fuses. It runs on automotive power and keeps the phone charged. If the external power goes away, it switches to batteries.

Please attach photos of your projects here.

Yesterday I got a Samsung SGH-E317 and a data cable. The data cable sells on Ebay for $5 including shipping. It is a USB cable, but the PC end has a USB-serial converter. If you cut the cable, you have a CMOS serial interface suitable for the tracker.

You must ground the DTR line, otherwise the phone will not respond to serial communication. This phone has a nice AT interface, and works fine at 4800 baud. There were a couple of minor code changes to make it work. The only significant problem is the GoPhone balance display causes the status light to blink, which would reduce battery life.

I do not recommend this phone for US users; get a C168i instead. However, the E317 has the same connector and serial interface as a large class of Samsung phones which are readily available around the world. This is a good solution for non-US users, who should not have the balance display problem.

The phones supported by this cable are: X426, X427, E105, X105, E715, D410, E315, E316, E317, X475, C225, D410, D415, E715, V200, V205, V206, X105, X475. Any of these would probably work with the tracker, but this has not been tested.

My Motorola T720 should be arriving soon. I will test the T720, and then combine all the modifications into a new build that supports the C168i, T720 and other Motorola, E317 and other Samsung, and Wavecom modules. This will be build 0.18 and should be posted in a few days if all goes well.

The Motorola C168i, used by the tracker, is free until May 10th at Best Buy. Buy a $25 GoPhone card (which extends your service for 3 months) and get the phone free. No sales tax either - $25.00 out the door. I just bought one for a friend’s tracker. Grab them before this hits SlickDeals and the stores get cleaned out. Thank you Corbin for emailing me about this deal.

Please post here when you start building a tracker.