Power Bridge for Android – PBA

by Digital Logic R&D

Android Power Bridge (APB) is an inventive device, developed on the demand of our customers who use uFR Series readers with Android devices.

It finally makes it possible to have an Android device charged while using our uFR readers at the same time, on the very same USB port.

Most Android devices provide power supply through a single micro USB port. This drawback excludes an option to have any accessory device connected at USB port permanently, simply because the Android device must be charged occasionally (“from time to time”), when the battery is empty.

If the user needs the constant use of an Android device, occasional charging (“from time to time”) in reality becomes “system downtime”, because the accessory device can not be used while the battery is charging.

The latest models of Android devices also use OTG (“On-The-Go”) USB mode, which is very convenient: Android can act both as a Master or a Slave device, depending on the info it receives from the USB port. Still, OTG does not enable Android devices to be charged while using the accessory device.

For all the reasons mentioned above Digital Logic launched Android Power Bridge (APB) project. After substantial research and development, we made a sort of breakthrough in this field, developing a unique APB device.

What is possible with our APB?

User can connect Android device, uFR Series reader, and battery charger thru APB, all at once:

  • Android devices will get power for constant charging.
  • uFR Series reader will be powered.
  • Both Android and uFR Series readers will communicate with each other.

If the charger is unplugged from APB, the uFR Series reader will remain powered by the Android device.

If the charger is plugged to APB again, the Android device will be powered again too, preserving communication with uFR Series reader.

Who is it made for?

Anyone who develops on the Android platform and uses our uFR Series reader devices. APB is a long-expected turnkey solution for the continuous operation of affordable Android hardware.

What is so good about APB and what makes it different?

  • Implementation is very easy. We provide our DLReader class in Java for communication with the uFR Series reader device, exposing an interface to a higher level of application for direct API calls.
  • We provide software examples with source code, for the quick start of the development.
  • In 99,9% of the cases, if you used uFR Series reader earlier with an Android device, you will only need to implement a new DLReader class into your existing project, keeping your code intact.
  • Long time support, provided through our regular and free updates.
  • APB is a firmware upgradeable device. Improvements and bug-fixes are available through firmware upgrade and regular updates, free of charge.

There are already some devices with a similar purpose, what is new and different?

Yes, there are already devices with a similar purpose on the market. Those devices use some tricks applied on specific Android hardware and not all Android hardware is compatible with them. Those devices are “tricking” OTG port operation on the “Sense” pin, this approach is potentially dangerous and could harm the device.

APB uses a significantly different approach.

How does it work?

In short, it has lots of stuff going on at the small piece of PCB, supported with sophisticated software written for specialized USB MCU.

APB has two modes:

  1. When power is present to APB, it acts as a mediator between the Android device and the uFR Series device, providing both of them with power and establishing a communication link at the same time by using AoA (Android Open Accessory) protocol ( https://source.android.com/devices/accessories/protocol.html ).
  2. If power is not present APB will automatically switch to OTG mode and power the uFR Series reader from Android device, without any need for swapping cables or similar operations.

Digital Logic APB is a professionally engineered device, made by following all engineering standards and rules of good practice, without using dangerous tricks or additional hardware from the market.

All the above facts sound like “magic”, are there some hidden weakness, faults, or limitations?

There is no magic, well-engineered hardware always knows its limits.

Limitations are:

  • At this stage of development, APB can be used only with our uFR Series reader devices.
  • Charging is slower and is defined by USB 2.0 standards, which means that the maximum charging current can’t be higher than 500 mA. Compared to standard chargers, it can be 3 to 4 times slower.
  • Slower charging also defines that the power consumption of the Android device must not be higher than the charging power provided. It means that power-hungry rated options like 3G/4G and high brightness of the screen must be used with care.
  • Communication with uFR Series reader devices is established ONLY by using our dedicated Java class – “DLReader” class.
  • There is a time lag in a transition state from OTG to AoA mode and vice verse. It particularly depends on the Android device and USB chipset used. This time may vary from 1 to 10 seconds until the communication is established again. However, using the DLReader class makes these transitions transparent to the end-user.

APB device models with various types of connectors

APB comes in several different models/variations, depending on the connection types it supports.

These connection types include Micro USB, USB, RS232, and RS485.

Please see the table below for more information.

Notice: If the connection type you require is not displayed in the table, there is a possibility of developing a customized APB according to your requirements. Please contact us for more information.

DEVICE IMAGEAndroid Power Bridge -4Android Power Bridge -3Android Power Bridge -2Android Power Bridge
Micro USB cableUSB A FemaleMicro USB connectorMicro USB cable
USB A femaleRJ45Micro USBRS232
Micro USBUSB B FemaleMicro USB connectorUSB A female