Interface Signal Function Selection Restrictions and Considerations
CYW920706WCDEVAL Hardware User Guide Doc. No.: 002-16535 Rev. **
32
In CYW20706, it is available only for application-defined HCI commands and events; it is not for Bluetooth standard HCI
commands. In CYW20706, it is used to communicate with the external MCU and does support Bluetooth standard HCI
commands.
It supports a maximum baud rate of 3 Mbps. To configure for 3 Mbps use WICED Studio API:
uart_SetBaudrate(0, 0, 3000000)
Debug messages can be routed to the HCI UART. To do so, use:
wiced_set_debug_uart(wiced_debug_uart_types_t uart) // with
// uart=WICED_ROUTE_DEBUG_TO_HCI_UART
The API functions that support the HCI UART are defined in
wiced_hci.h
.
9.3.1 SWD Debugging with the HCI UART
The HCI UART interface may be used for SWD debugging. When used for debugging, the normal HCI UART function may
not be used. The device FW will auto-detect the presence of an SWD debugger if the SWDIO signal is connected to HCI
UART pin BT_UART_RXD and the SWDCLK signal is connected to BT_UART_TXD. In order to do this on the
CYW920706WCDEVAL board, the FTDI chip must be bypassed as described below in order to connect the HCI UART pins to
the SWD debugger.
9.3.2 Bypassing the FTDI chip
Bypassing the FTDI chip on the CYW920706WCDEVAL board can be necessary in scenarios where the HCI UART interface
needs to be used for another purpose, such as connecting to an external MCU, or if an SWD debugger is connected to the
HCI UART. In those cases, the UART must be disconnected from the FTDI chip to avoid contention. The FTDI chip can be
bypassed and the board can be powered in 2 different ways:
Powering the board from USB
1. Remove All jumpers on J26
2. Plug in the USB cable to power up the board as usual
Powering the board using External supply
1. Remove All jumpers on J26
2. Supply 3.3V to TP1
9.4 Peripheral UART
CYW20706 supports a peripheral UART (PUART). The following information applies to the peripheral UART:
It is primarily used to interface with peripheral devices (for example sensors) or a microcontroller, but can also be used to
support debugging.
It supports a standard two-wire serial interface (RX and TX) without hardware flow control and a four-wire serial interface
(RX, TX, RTS, and CTS) with hardware flow control.
Note:
When hardware flow control is not used, the application is responsible for servicing the TX FIFO before it empties
and the RX FIFO before it fills. If the application does not service the FIFOs, receive-data can be lost and transmit-gaps
can occur.
The default baud rate is 115200 bps, but other baud rates, such as 19200 bps, 38400 bps, 57600 bps, and 3 Mbps, are
also supported.
The RX and TX FIFO hardware buffer size is 256 bytes.
shows CYW20706 PUART bus-configuration options when a system design also uses the SPI1 interface
provided by CYW20706. In such a system, PUART_RX must be on the same group of pins (referred to as a “pad bank”)
as the SPI1 bus signals. Since a full SPI1 bus can only be supported on a certain group of pins, all SPI1 bus signals and
PUART_RX must be on the “upper pad bank”, which is P24 through P39.
If the CYW20706 SPI1 interface is not used, then several more PUART bus-configuration options (in addition to those shown
in
to determine the other available PUART bus-configuration options.
