OTG/USB/Charge/HUB…. WTF?!?!?

Connecting your tablet into a vehicle can be a bit of a brain teaser.  There are many different things to think of like how to wire a power source to keep your tablet charged when in use, and how to configure your tablet power settings so that it turns on/off when your car is turned on/off.

To top this all off we need to have a conversation about what type of connection to use when plugging into the Micro-USB port of your tablet.  This topic is absolutely simple if you’re thinking of just running power to your tablet to keep it charged and ready to go.  Simply use a Male right angle Micro-USB (for best clearance) to standard Male USB cable and connect it to a 5V power source.

Click here for an Example Cable

But How Do You Support USB Accessories?

What if you want to charge your tablet, but at the same time use a USB accessory?  While this may sound like a simple task of grabbing a standard “On The Go” (OTG) cable for a mobile device you’re actually mistaken.  Using a standard OTG cable will absolutely allow you to use a USB accessory.  It accomplishes this by placing the tablet into USB Host mode.  That way the tablet is the host, and the USB device plugged into the OTG cable is the client accessory.  Fantastic! Problem solved right?

Not so fast.  First lets talk a bit about the difference between a Micro-USB connection, and a standard USB-B port that you typically see in devices like your laptop or a USB hub.  A standard USB-B port has 4 wires.  A Micro-USB, like the one used in your tablet, has 5 wires.  So that makes you wonder… why the hell are they different?

That’s because to create a Micro-USB OTG cable where USB accessories can be used, the number 4 and 5 pin/wire are shorted together.  This shorting tells the tablet that it should switch to Host mode and become the power source for the USB accessory.

The problem here is that when a Micro-USB cable is shorted in this way it now is providing power to the accessory, no longer using the USB connection as a charging power source for the tablet.  So that means that you have an either/or scenario.  Either you have USB Host mode, OR, you have USB charging mode.  That becomes a problem when you need to charge the tablet at the same time as supporting USB accessories.

So What’s the Solution?

Luckily Samsung has provided a technical way to actually allow both charging and USB Host on their tablets.  This is accomplished by shorting out the 4 and 5 pin/wire with a resistor instead of a wire.  When you add this resistor the tablet will now continue to charge and it will also put the tablet into USB Host mode.  However, what that means is that the tablet no longer supplies a power source for the USB accessory so the accessory needs to get its power from somewhere else.  Below is a diagram of how you make this work by adding a resistor and an external power source for the USB accessory.

This kind of setup allows you to also take that USB Host port and plug it into things like a little 4-port hub to run multiple accessories over the USB connection.  So it’s actually a pretty cool system configuration allowing you to do lots of different things with your tablet.

Does that Mean I Have To Build This Myself?!?!

Nope.. Luckily there’s a solution on the market called the LAVA Simulcharge adaptor that does exactly this.  Provides a 5-pin Micro-USB connection to the tablet, shorts the 4 & 5 pin/wire with a resistor, has a Female standard USB-B connector for an accessory (or connection to a hub) and a Micro-USB connection that acts as a power source for your tablet charging and the power for the USB accessory.

You can find these LAVA adaptors around the web from the manufacturer or on Amazon, eBay, Staples etc.. We’ve taken one of these adaptors and tested it with our Samsung tablets to make sure that it actually does work.  We’ve tried a bunch of other “solutions” that make promises but don’t deliver.  LAVA has also provided a compatibility list of tablets they have tested.  As you can see from the below video it truly does work!


So there you have it… a Nerdy look into what makes this all work.  Hopefully this information was helpful 🙂



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