FT311D-32L1C-R datasheet(13/40 Pages) FTDI

13 / 40 page

DS_FT311D

USB ANDROID HOST IC Datasheet

Version 1.2

Document No.: FT_000660 Clearance No.: FTDI# 305

5.2.1 UART Mode Signal Descriptions

The UART signals are fixed on the I/O pins. Table 5.1 UART Interface, details the pins for each of the

UART signals.

Pin No

Name

Type

Description

uart_txd

Output

Transmit asynchronous data output

uart_rxd

Input

Receive asynchronous data input

uart_rts#

Output

Request to send control output

uart_cts#

Input

Clear to send control input

uart_tx_active

output

Transmit enable (typically used for

RS485 designs)

Table 5.1 UART Interface

Note:

The FT311D has to enumerate the Android device before receiving data from the UART device.

This can be implemented by disconnecting the UART TXD signal of external UART device connected to the

FT311D uart_rxd signal until after the FT311D has established the USB link with Android device.

The connection sequence should be:

1. Connect FT311D to Android and complete enumeration.

2. Connect the TXD of UART device to FT311D’s RXD then start to receive data.

There are two methods to implement this function:

1.When FT311D connects to the Android device and enumeration is completed, the USB_ERROR# will

become Logic 0 (default Logic 1). This signal can be used to control the TTL gate (74LVC2G241,

74LVC1G125 or others) ON/OFF such that the TXD/RXD lines are connected/disconnected.

Figure 5-3 UART RXD and TXD connection gated by Enumeration

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