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10 HCI USB TRANSPORT LAYER

The USB Transport Layer has been specified by the Bluetooth™ SIG, and allows HCI level communica-

tion between a host controller (STLC2416) and a host (e.g. PC), via a USB interface. The USB Transport

Layer is completely implemented in SW. It accepts HCI messages from the HCI Layer, prepares it for

transmission over a USB bus, and sends it to the USB Driver. It reassembles the HCI messages from USB

data received from the USB Driver, and sends these messages to the HCI Layer. The Transport Layer

does not interprete the contents (payload) of the HCI messages; it only examines the header.

11 CLASS1 POWER SUPPORT

The chip can control an external power amplifier (PA). Several signals are duplicated on GPIOs for this

purpose in order to avoid digital/analogue noise loops in the radio.

A software controlled register enables the alternate functions of GPIO[15:6] to generate the signals for

driving an external PA in a Bluetooth™ class1 power application.

Every bit enables a dedicated signal on a GPIO pin, as described in Table 14.

12 GPIOS

Table 14. GPIOs alternate functionalities

The signal brxen is the same as the brxen radio output pin. The signal not_brxen is the inverted signal, in

order to save components on the application board.

PA7 to PA0 are the power amplifier control lines. They are managed, on a connection basis, by the base-

band core. The Power Level programmed for a certain Bluetooth™ connection is managed by the firm-

ware, as specified in the Bluetooth™ SIG spec.

The WLAN signals, as described in section 7.12, can be enabled on GPIO pins.

The extra PCM sync signals, as described in section 8.7, can be flexibly configured on GPIO pins to con-

nect multiple codecs.

Involved GPIO

Description of alternate dedicated functionality

gpio0

No dedicated function

gpio1

WLAN 1

gpio2

WLAN 2

gpio3

WLAN 3

gpio4

WLAN 4

gpio5

(Used for USB reset pull.)

gpio6

Power Class 1 brxen

gpio7

Power Class 1 not_brxen

gpio8

Power Class 1 PA0 or PCM sync 1

gpio9

Power Class 1 PA1 or PCM sync 2

gpio10

Power Class 1 PA2 or PCM sync 3

gpio11

Power Class 1 PA3

gpio12

Power Class 1 PA4

gpio13

Power Class 1 PA5

gpio14

Power Class 1 PA6

gpio15

Power Class 1 PA7