STA2500D datasheet(48/57 Pages) STMICROELECTRONICS

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HCI transport layer

STA2500D

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Doc ID 16067 Rev 1

HCI transport layer

The STA2500D supports the HCI transport layer as defined by the SIG: H4 []. It is supported

in combination with UART and SPI mode. The STA2500D also supports an enhanced

version of the H4 protocol in combination with SPI mode.

8.1

H4 UART transport layer

The objective of HCI UART transport layer is to make it 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 115200 bps)

●

Number of data bits

●

Parity bit

:no parity

●

Stop bit

:1 stop bit

●

Flow control

:RTS/CTS

●

Flow-off response time :500 µs

The flow-off response time defines the maximum time that the STA2500D can still receive

data after setting RTS high.

RTS/CTS flow control is used to prevent temporary UART buffer overrun between the

Bluetooth Controller and the Host.

The RS232 signals should be connected in a null-modem fashion, i.e. the Bluetooth

Controller TXD output should be connected to the Host RXD input and the Bluetooth

Controller RTS output should be connected to the Host CTS input and vice versa.

If the Bluetooth Controller RTS output (connected to the Host CTS input) is low, then the

Host is allowed to send.

If the Bluetooth Controller RTS output (connected to the Host CTS input) is high, then the

Host is not allowed to send.

If the Bluetooth Controller CTS input (connected to the Host RTS output) is low, then the

Bluetooth Controller is allowed to send.

If the Bluetooth Controller CTS input (connected to the Host RTS output) is high, then the

Bluetooth Controller is not allowed to send.

Figure 23.

UART transport layer

BLUETOOTH

HOST

BLUETOOTH

HOST

CONTROLLER

BLUETOOTH HCI

HCI UART TRANSPORT LAYER

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