Add USB OTG To A USB Thumb Drive

Every hacker has a USB thumb drive on their keyring, filled with backup files and a way to boot up a broken computer. One feature that most are missing though is USB On The Go (OTG) support, which allows a USB device to act as a USB host, connecting to devices like cell phones and tablets.

That can be added with the addition of a USB OTG adapter, though, and [usbdevice] has produced a nice how-to on soldering one of these permanently into a USB thumb drive to create a more flexible device. It’s a simple solder-something-on-something-else hack, but it could be handy.

There are a few caveats, though: it needs a USB thumb drive with solderable headers, which most of the smallest drives that have connectors right on the PCB won’t have. Most of the larger drives will have these, though, and they are cheap, so finding a suitable victim isn’t hard.

33 thoughts on “Add USB OTG To A USB Thumb Drive

    1. I wonder how much signal integrity will suffer from the reflections caused by the extra unterminated connector spliced in.

      Plus the article is completely misleading, it does nothing to add USB OTG to the phone, it’s just a flash drive with two types of USB connector. It won’t work with non-OTG devices, it won’t even let you connect any other device.

      1. My rule of thumb says maximum stub length has to be lower than 1/10th of the signal rise time. (signal speed is roughly 15cm/ns on a PCB)
        For a rise time of 1ns, this would allow for 1.5cm stubs having no significant influence on the waveform. IIRC USB 2.0 HS (480Mb/s) has a rise time of 500ps, so make it short, or live with horribad signal integrity. Of course, i would say that the complete transmission-path does have an influence too. If you directly plug that stick in your OTG-phone, it can work, but if you plug it into your PC (over a 2m cable that’s not really up to USB spec either because the chinese money-savings engineer found a cheaper cable supplyer), it might just not work anymore…

          1. Shure, cheap drives do not deliver the flash speeds to fully use all the USB 2.0 bandwith. If you are unlucky, they easily drop below 5MB/s effective transfer. But it would be VERY strange if that had any infuence on the signal rise time of the USB physical layer. Or are these drivers so advanced that they allow adaptive dynamic slopes? If your PHY is built to be compliant with USB 2.0, i would guess that it’s drivers are designed to run fast enough slopes too.
            And you are right that the error correction in the physical layer can help a lot to fix reflections and impedance mismatches up to a degree, but there is only so much it can correct before transmission completely fails or is getting so bad you are back down at floppy drive speeds.

      1. Hate to agree but do. I just bought a 32Gb sandisk with both connectors for $20 at retail.
        Now if this was a hack about 5 years back it would have been great, but I hate to say it’s a hack inspired by something commercially available for buttons.
        it’s a hack, but it’s for the sake of it, when “value of own time” < "value of commercial solution".

  1. I just slit from the cable end the rubber shroud of a micro connector (not all the way) and soldered the floating pin on the end to the one next to it (+5). Glue the shroud closed with that tiny wire inside, from pins 4-5. The fifth pin at 5 volts tells the host to act. All micro USB’s seem to have 5 pins just 4 wires. Then connect the 4 wire cable to a salvaged case USB port desoldered from that little bit of board.

    1. You have that mixed up. Pin 5 is ground, not 5v. For otg to be enabled, pin 4 gets tied to pin 5 ground. I’ve been making my own micro USB cables and adapters for some time now.

    1. those micro adapters are less than an inch in length. the one i got came with a Verbatim flash drive. ( Model 49821 ) and the “Store ‘n’ Go Dual USB Flash Drives for OTG Devices” seem small enough as well. mostly i use the micro adapter for wireless mouse or keyboard+trackpad, with a tablet.

    1. Perhaps because pretty much the only useful thing you can do with a device with a male micro-USB connector is plug it into a OTG capable port? If you Google “OTG flash drive” you can also find similar off-the-shelf products.

      1. But it’s still misleading it has nothing to do with USB OTG it’s just a connector. You can google freenergy too, will find lots of stuff, but it still doesn’t make
        Perpetum mobile proved…

        1. Super late reply but OTG uses a micro usb connector with the GND and SIGNAL connected with a resistor. A regular micro usb connector wont work since the SIGNAL pin is not connected to ground. So this is a OTG adapter that will work with OTG compatible devices. Just soldering in a regular micro usb connector wont work with OTG compatible devices since they would not know that they should power the device connected.

  2. It’s definitely *NOT* acting as a USB host. If you’re plugging it into a phone, the *phone* is the host. If you plug it into something that can’t be a host (like older phones) then it won’t work.

    1. Nice, but it requires root. :-( Which is difficult and dangerous on a Galaxy S5. If you do not wamnt to trigger the “Knox Counter” and the “yellow triangle” than you have to downgrade the software, then hack it with an exploit and upgrade again. And not make any fatal mistakes during the procedure.

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