DS_FT312D Datasheet, PDF (7/25 Pages) List of Unclassifed Manufacturers – Future Technology Devices International Ltd.

DS_FT312D USB ANDROID HOST IC Datasheet
Version 1.0
Document No.: FT_000816 Clearance No.: FTDI# 331
4 Function Description
The FT312D is FTDIs second dedicated Android Open Accessory Mode integrated circuit device or Android
Host. The FT312DUSB host port is dedicated to support of the Android Open Accessory class and will
bridge data between this port and the UART interface.
4.1 Key Features
Easy to use Android Open Accessory IC translating the Device port of the Android device into UART
capabilities
4.2 Functional Block Descriptions
The following paragraphs describe each function within FT312D. Please refer to the block diagram shown
inFigure 2.1.
4.2.1 UART Interface Module
The FT312DUART module controls the UART interface providing basic RXD, TXD signalling with
RTS#/CTS# hardware flow control. An additional TX_Active signal is supplied to control external RS485
transceivers for users wishing to create a USB to RS485 bridge. The UART supports baud rates from 300
baud to 921600 baud. A full description of the UART module is provided in Section 5.
4.2.2 Buffers
The FT312D provides internal buffering between the USB port and the UART port of the IC for smooth
data streaming.
The Android device can send NAK’s to the USB OUT token sent from the FT312D. This can happen when
the UART application on the Android is running in the background or multiple applications are launched in
the Android device. When the UART application on the Android device is not accepting data, the data will
be buffered in the UART RX buffer in FT312D. The UART RX buffer size is 5512 bytes.
The UART_TX buffer which stores data from the USB port, heading for the UART is 256 bytes.
4.2.3 USB Host
The USB Host block handles the parallel-to-serial and serial-to-parallel conversion of the USB physical
layer. This includes bit stuffing, CRC generation.
4.2.4 USB Transceivers
USB transceiver cells provide the physical USB device interface supporting USB 1.1 and USB 2.0
standards. Low-speed and full-speed USB data rates are supported. The output driver provides 3V3 level
slew rate control signalling, whilst a differential receiver and two single ended receivers provide USB
DATA IN, SE0 and USB Reset condition detection. These cells also include integrated internal pull-down
resistors as required for host mode.
4.3 Default Descriptor Strings
When the USB port is connected to the Android USB port, the Android platform will determine which
application to load based on the strings read from the FT312D. These strings are configurable with a
Windows utility: FT312D_Cofiguration available for download from the FTDI website.
http://www.ftdichip.com
Please refer to the application note AN_236 User Guide for FT312D Configuration to change the default
string values.
Copyright © 2013 Future Technology Devices International Limited
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