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BTM41 DATASHEET

13

5.6

Serial Interfaces

5.6.1

UART

This is a standard UART interface for communicating with other serial devices. The UART

interface provides a simple mechanism for communicating with other serial devices using

the RS232 protocol.

When the module is connected to another digital device, UART_RX and UART_TX

transfer data between the two devices. The remaining two signals, UART_CTS and

UART_RTS, can be used to implement RS232 hardware flow control where both are

active low indicators.

5.6.2

USB

There is a full speed (12M bits/s) USB interface for communicating with other

compatible digital devices. The module acts as a USB peripheral, responding to request

from a master host controller, such as a PC.

The module features an internal USB pull-up resistor. This pulls the USB_DP pin weakly

high when module is ready to enumerate. It signals to the USB master that it is a full

speed (12Mbit/s) USB device. The USB internal pull-up is implemented as a current

source, and is compliant with section7.1.5 of the USB specification v1.2. The internal

pull-up pulls USB_DP high to at least 2.8V when loaded

with

a

15k

±5%

pull-down resistor (in

the hub/host) when

VDD

=3.1V. This presents a The

venin resistance to the host of at least 900 . Alternatively, an external 1.5k

pull-up

resistor can be placed between a PIO line and DP on the USB cable.