STLC2500
Table 23. GPIO multiplexing
WLAN
(See also table 19.)
WLAN 1
WLAN 2
WLAN 3
WLAN 4
Multiplexed GPIOs
I2C
PCM
I2C clock
I2C data
[PCM or GPIO]
[PCM or GPIO]
[I2C or GPIO]
[I2C or GPIO]
PCM sync 1
PCM sync 2
GPIO
GPIO 0
GPIO 1
GPIO 2
GPIO 3
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
BLUETOOTH
HOST
BLUETOOTH HCI
BLUETOOTH
HOST
CONTROLLER
HCI UART TRANSPORT LAYER
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