STA2500DTR STMICROELECTRONICS [STMicroelectronics], STA2500DTR Datasheet - Page 48

• Manufacturer Part Number: STA2500DTR
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

HCI transport layer
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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.
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:
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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
Baud rate
Number of data bits
Parity bit
Stop bit
Flow control
Flow-off response time :500 µs
BLUETOOTH
HOST
:configurable (default baud rate 115200 bps)
:8
:no parity
:1 stop bit
:RTS/CTS
Doc ID 16067 Rev 1
HCI UART TRANSPORT LAYER
BLUETOOTH HCI
CONTROLLER
BLUETOOTH
HOST
STA2500D