Using GPS from A9g (TEL0134) - Vehicle tracking

Hi forumsters! :wink:
I received the GPS from A9g (TEL0134) from Core a couple of days ago and I am hitting my first problems.

Project: Building a GPS tracker (and accelerometer) as a component of a security system for my campervan. I just need it to provide geo-location, say every minute, via the serial link of the board.
Using other controllers I can pick up the feed and pass it through cellular to a server/app and then track movement.
I will post more in the project area over time, but here is a bit of an intro. I already have a PIR, Noise (smoke/CO detector), camera etc.which can be remotely controlled and responses in the form of lights buzzers etc. The intention of the solution is to have multiple devices spread through the vehicle that would monitor various conditions/events and then react. They can send push notifications to my phone and data to IOT cloud. They all continuously monitor each other and with 2 cellular devices connecting to the Internet it would be hard to break-in/steal from or drive away the vehicle without detection.

GPS from A9g (TEL0134):
I have it connected up on a breadboard and it is initialising and some basic commands are working

AT+RST=1
OK
Init...
NO SIM CARD
+CIEV: "Charging",89%

+CREG: 2
AT+CGMI
Ai_Thinker_Co._Ltd.
OK
AT+CGSN

867959034522473
AT+CIPSTATUS
+CIPSTATUS:
STATE:IP INITIAL 

But trying to follow the tutorial …

AT+GIZTRACKER=1,0,10,1

+GIZWITS: register fail

+CME ERROR: 50
Dns,fail,try url

failure, pelase check your network!

Several other commands return errors (generally 58) …

*AT+CWLAP?*

*+CME ERROR: 58*  -- This may be that the device has no Wifi?

I have created the QR code as instructed in the tutorial but I cannot see what I am to do with it?
The tutorial mentions the APP which I cannot identify(any ideas?)
I have created an account on Gizwits and the related GITHub isn’t helping!!

Has anybody got further than this with the board?

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UPDATE: The instructions in the tutorial to use the GPS tracking app seem to be a red-herring (at least in AUS :australia:). To use the app you need to have a SIM inserted and the system able to receive an SMS authentication. I should be able to get :satellite: GPS location without mobile connection, shouldn’t I? :thinking:

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Hi Mick,

Welcome to the forum!!

It makes sense that you are able to get information from the GPS module,

I would try running the following two AT commands:

AT+GPS=1
AT+LOCATION=1

I’m pretty sure this runs independently of any SIM services so it should be good to go! A link to the Wiki.

Liam.

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Hi @Liam,
I know I am close but those commands are recd OK but give ‘No Location’. The GPS retries every 10 secs.

AT+GPS=1

OK

+CREG: 2

AT+LOCATION=1

COMMAND NO RESPONSE!

Are you able to confirm if it is vital to have a battery connected? It is not mentioned in the tutorial but I have seen some posts suggesting it is required although the rationale is to provide high current on cellular sessions.
I am in a position where my iPhone is receiving a strong GPS signal so something is preventing the response. Battery? Aerial? Config?

Thanks for the link but beyond the hardware description its all about the tracker app and GizWits and registering the device which I don’t think should be required for GPS only

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Hi Mick,

Hmmm, would it be possible to send through a photo of your setup?

Without a schematic its a bit hard, Core has some in stock at the moment so we can bust one out for testing. Comparing another GPS module, the NEO-6M that one only uses 67mA according to the datasheet, which is far less than USB’s lowest current spec (USB 1.0 supplies 500mA).

Yeah I dont think its required, we’ll get this figured out though!
Liam.

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Hi Liam
Thank you. :+1:
Attached is the setup. Very simple. I have a CH340 UART board to connect to USB on my PC running the AI-Thinker serial tool - This is sending and receiving through the yellow and orange leads fine.
Power is taken from a separate USB on the hub (common GND).
Next thing is to add the ‘battery’ from a bench supply - I’ll let you know!
I have added my multi-meter in line and it shows 30mA rising to 40mA when actively looking at GPS

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RESOLVED!!! but BAD NEWS
As shown below in the transaction log.

  1. There needs to be a battery connected (4.3v) to start the GPS (weird!) :exploding_head:
  2. Having started/enabled GPS it is no longer required - i.e. it is a firmware check
  3. The AT+LOCATION=1 gives no response
  4. The AT+LOCATION=2 provides the correct coordinates

The BAD NEWS: I was adjusting the ‘battery’ voltage on the bench supply to determine where the on board charger came in and dropped out. But I hit the coarse voltage and smashed out 7v before realising.
The board still talks to me but not the GPS!!! - I have cooked it!!! :fire:

// No Battery
Init...

NO SIM CARD
+CIEV: "Charging",89%

AT+GPS=1

OK
AT+LOCATION=2
+LOCATION: GPS NOT FIX NOW
+CME ERROR: 52
AT+LOCATION=1
COMMAND NO RESPONSE!
AT+LOCATION=2
+LOCATION: GPS NOT FIX NOW
+CME ERROR: 52

//4.3v supply attached to 'BAT'

AT+LOCATION=2

-37.814523,144.886513  //NOTE:  real coords replaced with Flinders St Station;)

OK


//4.3v supply DISCONNECTED from 'BAT'

AT+LOCATION=2
7.814523,144.886513 
2 Likes

Hi Mick.
A couple of things wrong with your measurement set up.

  1. Your meter is set to measure AC current. Should be DC.
  2. the 'voltage burden" on that range could be quite high. The internal resistor in the meter on milliamp ranges is usually quite high and is effectively in series with the load. This means you may drop too much voltage in the meter itself thus reducing the voltage to the device under test (DUT). Could be to the point where the DUT no longer works or at least does not work in a real world manner. the solution is to use the 10A range where the internal resistor is so low it can usually be ignored. You should still get mA (0.001A) resolution on this range.
    Cheers Bob
    PS. The mA ranges are usually OK on high voltage circuits where the voltage drop is a much smaller percentage of the applied volts. This drop could be more than 1V which with 5V or 3.3V circuits in some cases would shut down the DUT.
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Lol - Thank you @Robert93820
It was merely to test that the draw from the USB 2 socket was not excessive.
The real problem was the lack of the battery supply to the board when trying to start the GPS.

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How do you know it was not excessive. What you measured on the AC range could have been anything.

Also what you measured on a milliamp range would not mean much in the real world when the DUT gets the full 5V.

Your best bet when trying to measure USB volts and current would be one of the USB monitoring devices which display voltage and measure current with a Hall device which is pretty much non invasive. The voltage drop is only a few mV.

I am only trying to help here and point out some errors in your measuring techniques and explain some of the consequences possible. If you think this is a joke and worthy of a “Lol” (this used to mean “little old lady”) when you smell that distinctive odour and see the green and brown smoke you might sit back and reflect a bit.
Cheers Bob

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Hi @Robert93820, Don’t take offence! I was laughing at my own stupidity!
It was also my carelessness that over-voltagaged the board and took out the GPS circuit just after I had resolved the primary issue.
I appreciate the risks of making measurements with a DVM but it was an attempt to ensure that the current was not exceeding the 500mA supply of the USB2. This was in response to a response to @Liam, trying to confirm that this board from Core should be OK.
I thank you for your helpful comments and respect your knowledge in the field of measurement.
Cheers Mick

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