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Author Topic: USB chargers  (Read 3255 times)
N1DVJ
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Posts: 530




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« on: March 17, 2011, 01:35:26 PM »

I want to put a second Magellan Roadmate in my car 'semi permanantly'.  But I only have 1 car charger. 

No problem.  Little 5V USB 'plugs' are less than $5.  Just wire one in behind the dash and feed the USB cable to the GPS and it should charge.

Well, it DOES charge.  But it also puts the GPS into file mode to read it via a PC and it won't work as a GPS.  I tried cutting the data and clock line free in a spare USB cable but no go, the GPS STILL goes into file mode and won't work.

I don't want to cut up my only car dc adapter for the thing.  Does anyone know how the thing works?   I may have to order a mini-usb male and female connector and see what's going on.

Mike
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N3OX
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« Reply #1 on: March 17, 2011, 02:49:30 PM »

Mini and micro USB have a fifth "device ID"  pin that I understand is sometimes simply connected up inside the connector itself.

Investigate the device ID pin on your car charger... see if it's grounded, floating or some other resistance.  You may have to duplicate that behavior on your home-made cable.

Take a look here:  http://en.wikipedia.org/wiki/USB_On-The-Go
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
W8JX
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« Reply #2 on: March 17, 2011, 03:27:46 PM »

I have never had a "ID' problem and have swapped out a lot of USB chargers as long as the plug style matches. Some might charge at faster or slower rates but they work.
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All posted wireless using Win 8.1 RT, a Android tablet using 4G/LTE/WiFi or Sprint Note 3.
N1DVJ
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Posts: 530




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« Reply #3 on: March 18, 2011, 02:46:48 AM »

Took one cable and cut it and have been playing with it.  Nothing I do seems to affect it.  No matter what, a generic connect and the unit says it's connected to a PC.  Whatever it is, if it's in the '5th' pin, it's in the connector, and I'll have to make up a small feedthrough to figure it out. 

It still might be resisitors setting voltage levels on the clock and data lines, and I'll look into that.  Apple plays that game.  The USB spec actually allows that for setting charging currents, but Apple goes beyond the spec.  That's why you're seeing 'special' car chargers now with a 2.1A tap on them.  A lot of devices now go to the 1A level using that on the USB.  I wonder...  Like I said, I'll have to make up a small feed through to figure it out.

Mike
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N1DVJ
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« Reply #4 on: March 18, 2011, 06:04:16 AM »

OK, here's what I found out so far.  Some of this came from a Russian site that specializes in pinouts of anything and everything.

The 5-pin Mini-USB obviously has 1 extra pin over USB.  But it is not pin 5.  The Mini-USB numbers 1-2-3-X-4 where pins 1 through 4 corespond to regular USB pins 1 through 4.  Pin 1 is +5v and pin 4 is ground.

Pin X is the important one, and here's what they say is used for Nuvi, and at least 2 others.  I couldn't find specific info on the Magellan RoadMate, but at least this gives me a place to start.  Notice that this is NOT the scheme that Apple uses to set their charging.  Note that there appears to be a 'standard' that pin X is connected to ground through a 200K resistor, but I haven't personally ohmed out any cables yet.

---- From http://pinouts.ru/GPS/garmin_nuvi_power_pinout.shtml --------

Nuvi behavior depends on mini-USB plug connection. (IMHO) it is like this:
pin X not connected - data cable, nuvi connects to PC as removable drive, navigation NOT possible.
pin X & 4 short-circuited - USB supply 500mA, possible navigation,
pin X & 4 connected through 18kOhm resistor - Garmin supply 1A, possible navigation.


I personally modified a cable that connected pin X to pin 4 (shorted), and verified the 500 mA charge behavior as noted
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KC8IUR
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« Reply #5 on: March 18, 2011, 06:26:00 AM »

Read up on "USB-Spec" chargers at www.adafruit.com She had to go through a few revisions of her minty-boost product to get it to work with everything. Lucky she's a EE and documents her methods.
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N1DVJ
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« Reply #6 on: March 18, 2011, 06:47:24 AM »

I've seen the minty-boost info before.  In fact, that was where I learned what was going on with Apple (we use an interface for iPads here at work) but the key there is that they use 'generic' cables.  It's the charger that defines (via resistors) what the device does.   It's a great resource!!

However, with GPS units, it appears it's the CABLE that defines what the device does. 
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KC2MMI
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« Reply #7 on: March 18, 2011, 04:46:34 PM »

Mike, Magellan used to be quite nice about answering the phone and their email, have you tried contacting them?

In theory a plain mini/microUSB cable will have all four traditional lines implemented, but it should NOT have anything connected to that new fifth "indicator" line. If you've got cheap Chinese cables or cables from some dedicated device--it might very well. And as you've found out, that new cable has to be neutered, and then the GPS should simply charge when it sees power--since there will be no data or indicator connections.

I'm guessing that it is also possible, if the adapter is the typical new dc-to-dc digital voltage converter, that enough RFI could get past a cheap adapter to make the GPS *think* it is seeing data signals, and a GPS that is too smart might just make that assumption. Magellan could tell you if that's possible.

I need a dual-USB adapter, and figuring if I need dual now I'd better put in a triple, which is hard to find, that I might just used a 7x05 and a power transistor, because the cheapier adapters all split 1000mA total, and the new smartphones are pulling 850mA EACH.
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N1DVJ
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Posts: 530




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« Reply #8 on: March 18, 2011, 05:02:03 PM »

I just speced out a SCOCHE (I don't think I spelled that right, I can find it next week in you need it) adapter for work.  It has 2 USB ports on it.  One is rated 1A, and the other is rated 2.1A and pulls the resistor bias trick on the clock and data lines to let the iPad pull the full 2.1A 

I found them a number of places for under $20.

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N1DVJ
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Posts: 530




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« Reply #9 on: March 21, 2011, 03:42:13 AM »

And for the people following this thread but not posting...

I found one site that refered to a 'dedicatated charger mode'.  That is when the charger has the clock and data lines tied together but to nothing else.  That's an easy one to try, so I'll give that a whirl today.  

Update:  Tried this trick on the RoadMate, no difference.  So, it's probably the X pin I have to tamper with.
« Last Edit: March 21, 2011, 05:41:21 AM by N1DVJ » Logged
N1DVJ
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Posts: 530




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« Reply #10 on: March 22, 2011, 06:25:13 AM »

Well, heard back from Magellan.  After 2 emails, the first saying buy a home charger, they said:

"Since it's not recommended to wire your Magellan GPS unit into your vehicle system, we don't have the correct procedure to do it and it's outcome. Your GPS may or may not work, however, you may try searching on-line for the proper procedure."

It was sort of expected.  The non-commital we won't be liable response.  Oh well...

Well, once I figure out what it is, I WILL post it here!

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N1DVJ
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Posts: 530




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« Reply #11 on: March 22, 2011, 11:07:35 AM »

Well, it's definately in the plug.  The Mini-USB plug on the end of the charger cord. 

I have some Mini-USB Male/Female extension cables that do NOT take Pin X across, only pins 1 through 4.  If I use that on the factory charger, the GPS things it's attached to a PC.  So, I have to order some male and female Mini-USB connectors and make up a small extension cable that takes all 5 across to verify, then look at what the Magellan charger does, and then finally make a short extension that makes any cable appear as Magellan.

More later, after I get the connectors...
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