Google unveiled the Android Open Accessories initiative a little over a year ago. The specification uses industry standard USB technology with an additional enumeration step. As a result the USB connection allows the Android platform to function as a USB slave/peripheral eliminating the need to source power, store class drivers, and support the USB host stack, which has responsibility for controlling the USB bus. In the end, the USB host functions are now relegated to the end product which is connecting to the Android platform.
Running off a standard 3.3 V supply and drawing a current of just 25 mA in full operation at 48 MHz and 128 µA while in standby mode, the FT311D has the capacity to bridge the USB port to six different user selectable interface types, namely GPIO, UART, PWM, I2C master, SPI slave and SPI master. It can be utilised in conjunction with any platform that supports the Android Open Accessory mode (typically Version 3.1 of the Android operating system onwards, though some platforms may back-port Open Accessory mode to Version 2.3.4).
When the IC’s peripheral interface is configured in UART mode, the interface implements a basic asynchronous serial UART port with flow control. The FT311D’s UART can support data rates of between 300 bit/s and 6 Mbit/s, while its I2C master interface can connect to I2C slave interfaces supporting speeds of up to 125 kbit/s. The interface can also be configured to provide 4 pulse width modulation (PWM) outputs. These can be used to generate PWM signals for controlling the motors, actuators, sensors, DC/DC converters and AC/DC supplies found in such systems, as toys, lighting applications, home automation, and industrial equipment.
A development module (UMFT311EV) based on the FT311D is also available and is intended for use as a hardware platform to enable easy evaluation of the IC and allow engineers to develop a broad range of Android Open Accessory compliant applications.
“With this new host IC, we have strengthened our portfolio of Android related products for engineers to explore the new possibilities that the Open Accessories mode offers,” states the company’s CEO and founder Fred Dart, “Through this chip, plus our development tools, software and application support, our goal is to make USB host integration into customers’ end products as easy as it is our R and X-Chip series devices.”
The FT311D is supplied in 32 pin QFN and LQFP package options. These ICs have an operational temperature range that covers -40 ⁰C to 85 ⁰C.