User's Manual

18
Physical Interfaces
7.1 UART Interface
WT11 Universal Asynchronous Receiver Transmitter (UART) interface provides a simple
mechanism for communicating with other serial devices using the RS232 standard
1
.
UART_TX
UART_RX
UART_RTS
UART_CTS
WT12
Figure 8: WT11 UART interface
Four signals are used to implement the UART function, as shown in Figure 11.12. When
WT11 is connected to another digital device, UART_RX and UART_TX transfer data
between the two devices. The remaining two signals, UART_CTS and UART_RTS, can be
used to implement RS232 hardware flow control where both are active low indicators. All
UART connections are implemented using CMOS technology and have signaling levels of
0V and VDD_PADS.
Figure 9: WRAP THOR VM Stack
In figure above, the iWRAP software solution is described. In this version of the stack
firmware shown no host processor is required to run the Bluetooth protocol stack. All
software layers, including application software, run on the internal RISC processor in a
protected user software execution environment known as a Virtual Machine (VM).
The host processor interfaces to iWRAP software via one or more of the physical interfaces
which are also shown in the figure above. The most common interfacing is done via UART
interface using the ASCII commands supported by the iWRAP software. With these ASCII
commands the user can access Bluetooth functionality without paying any attention to the
complexity which lies in the Bluetooth protocol stack.
The user may write applications code to run on the host processor to control iWRAP
software with ASCII commands and to develop Bluetooth powered applications.
Notes:
More details of iWRAP software and it’s features can be found from iWRAP User Guide
which can be downloaded from www.bluegiga.com
.