STLC2500

20/23

Table 23. GPIO multiplexing

8.5 The I2C interface

The I2C interface (version 2.1) has been specified by Philips.

The I2C interface is used to access I2C peripherals.

The implemented interface is a fast master I2C; it has full control of the interface at all times. I2C slave

functionality is not supported, forcing attached devices to be slave, otherwise bus contention will occur.

9

HCI UART TRANSPORT LAYER

The UART transport Layer has been specified by the Bluetooth SIG and allows HCI level communication

between a Bluetooth controller (STLC2500) and a Host (e.g. a GSM), via a serial line.

The objective of this HCI UART Transport Layer is to make possible to use Bluetooth HCI over a serial

interface between two UARTs on the same PCB. The HCI UART Transport Layer assumes that the UART

communication is free from line errors.

UART Settings

The HCI UART Transport Layer uses the following settings for RS232:

– Baud rate: configurable (default baud rate 115.2 [kbps])

– Number of data bits: 8

– Parity bit: no parity

– Stop bit: 1 stop bit

– Flow control: RTS/CTS

– Flow-off response time: 3 ms

Flow control with RTS/CTS is used to prevent temporary UART buffer overrun. It should not be used for

flow control of HCI, since HCI has its own flow control mechanism for HCI commands, HCI events and

HCI data.

If CTS is high, then the Host/Bluetooth controller is allowed to send.

If CTS is low, then the Host/Bluetooth controller is not allowed to send.

The flow-off response time defines the maximum time from setting RTS low until the byte flow actually

stops. The RS232 signals should be connected in a null-modem fashion, i.e. the local TXD should be con-

nected to the remote RXD and the local RTS should be connected to the remote CTS and vice versa.

Figure 9. UART Transport Layer

Multiplexed GPIOs

WLAN

(See also table 19.)

I2C

PCM

GPIO

WLAN 1

I2C clock

[I2C or GPIO]

GPIO 0

WLAN 2

I2C data

[I2C or GPIO]

GPIO 1

WLAN 3

[PCM or GPIO]

PCM sync 1

GPIO 2

WLAN 4

[PCM or GPIO]

PCM sync 2

GPIO 3

BLUETOOTH

HOST

BLUETOOTH

HOST

CONTROLLER

BLUETOOTH HCI

HCI UART TRANSPORT LAYER