WT21-A-HCI Ver la hoja de datos (PDF) - Unspecified
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WT21-A-HCI Datasheet PDF : 57 Pages
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6
Host Interfaces
6.1
Host Selection
The MCU selects the UART/SDIO interfaces by reading PIO[4] at boot-time. When PIO[4] is
high, the SDIO interface is enabled; when PIO[4] is low, the UART is enabled.
If in UART mode, the MCU selects the UART transfer protocol automatically using the unused
SDIO pins shown in Table 9
SDIO_CLK
0
0
1
1
SDIO_CMD
0
1
0
1
Protocol
bcsp
h4
h4ds
h5
Table 9: SDIO_CLK and SDIO_CMD transfer Protocols
6.2
UART Interface
This is a standard UART interface for communicating with other serial devices.
WT21 UART interface provides a simple mechanism for communicating with other serial devices
using the RS232 protocol.
Note:
WT21 uses RS232 protocol, but voltage levels are 0V to VDD_PADS (requires external RS232
transceiver chip.
UART_TX
UART_RX
UART_RTS#
UART_CTS#
Figure 7: Universal Asynchronous Receiver
Four signals implement the UART function, as shown in Figure 8. When WT21 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.
Bluegiga Technologies Oy
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