STLC2500ATR datasheet(34/37 Pages) STMICROELECTRONICS

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HCI UART transport layer

STLC2500A

34/37

HCI UART transport layer

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

communication between a Bluetooth Controller (STLC2500A) 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:

–

Parity bit:

no parity

–

Stop bit:

1 stop bit

–

Flow control:

RTS/CTS

–

Flow-off response time:

3ms

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

flow actually stops.

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

Bluetooth Controller and the Host.

It should not be used for flow control of HCI, as HCI has its own flow control mechanism for

commands, events and data.

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 high, then the

Host is allowed to send.

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

Host is not allowed to send.

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

Bluetooth Controller is allowed to send.

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

Bluetooth Controller is not allowed to send.

Figure 14.

UART transport layer

BLUETOOTH

HOST

BLUETOOTH

HOST

CONTROLLER

BLUETOOTH HCI

HCI UART TRANSPORT LAYER

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