Downloading FTDI dive log using desktop Subsurface on Android

Richard Houser rick at
Wed Feb 8 07:11:58 PST 2017

OTG deals primarily with the handset portion, not the devices you plug into it.  So, except for the handset, OTG adapter, and power requirements, devices aren't OTG compatible or not.  OTG adapters actually signal in hardware (via a specific resister value, like cables in USB-C) for the device to flip it's mode from a normal device and instead drive the USB bus.  I actually have two non-compliant devices that can be modded to work: Nexus 4 (incorrectly gives 3.3V instead of 5V) and an HP touchpad (doesn't enter the OTG mode unless it's also receiving power, necessitating an additional Y cable to inject power or an OTG hub I have that backfeeds power).

I think what you will find is that most of those devices with both USB-A and micro-USB actually are just a normal USB device with an extra micro connector wired as an OTG adapter.  If your device is already supporting OTG with that secondary connector. Your unit should also work on normal hardware like a keyboard via a traditional OTG adapter that looks like this:

My guess is during the failure you were connecting your devices with a USB-A to micro-USB adapter that is not an OTG adapter (they could look physically identical, but the resistance would not be correct to signal OTG mode).

On February 8, 2017 8:42:53 AM EST, Willem Ferguson <willemferguson at> wrote:
>On 08/02/2017 13:36, Anton Lundin wrote:
>> Basically you can't connect anything else to you phones usb-port than
>> the USB-OTG cable. You might be able to use a USB-OTG-cable which
>> injects power but nothing else. You might be able to use a usb-hub
>> the power inject, but I've never seen one which can feed power to a
>> USB-OTG connected phone.
>> Remember USB-OTG != USB. They are two completely different modes in
>> usb-hardware and software in your Android device.
>> If you simultaneously need adb access, you need to enable adb over
>> and connect to your Android device that way.
>> //Anton
>Anton, I need a bit of help here to understand how an OTG protocol
>communicate with a normal non-OTG USB device like a dive computer. I 
>have always assumed OTG is a software upgrade to the existing USB 
>infrastructure that allows a device to become USB bus master and 
>actively talk to other USB devices. Now I see that there are so-called 
>OTG adapters that allows a memory stick to be OTG-compliant. Does this 
>mean that only OTG-compliant devices can be accessed by Android? What 
>exactly in hardware is required to get my phone to talk to a non-OTG 
>dive computer? I happen to have a memory stick with a micro-USB plug as
>well as a full-sized USB plug. If I connect it to Android with the 
>full-sized end, the OTG detector on my phone does not register it. If I
>switch to the micro-USB end of the memory stick, it registers an OTG 
>device on Android. I need to understand what the equipment
>are for a diver with a FTDI-nased deive computer.
>Kind regards,
>subsurface mailing list
>subsurface at

Sent from my Android device with K-9 Mail. Please excuse my brevity.
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