Host interfaces

SPWF04SA, SPWF04SC

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DocID029757 Rev 5

7

Host interfaces

SPWF04S supports UART and SPI interfaces for connecting the module with a host

processor. The pins to be used in the two possible configurations are indicated in the Table

5: "Pinout description". By default, SPWF04S works using the UART port with AT

commands. To switch SPI on, the pin corresponding to GPIO[9] must be driven high during

boot to force the device to handle incoming commands over SPI instead of UART.

7.1

UART interface

The SPWF04S can be interfaced with an external host using the UART interface shown in

Figure 2: "UART connection with host device". This configuration is used by default, with

four signals including RTS and CTS for HW flow control. The UART baud rate is

configurable in the 1200-921600 range. The default configuration is 115200/8/n/1 with flow

control disabled.

Figure 2: UART connection with host device

7.2

SPI interface

The SPWF04S can be interfaced as a slave with an external host by using the SPI

interface as shown in Figure 3: "SPI connection with host device". There are four SPI

signals and an additional host interrupt signal. SPI signals are detailed in the Table 7: "SPI

signals". This Interrupt signal allows the SPI slave to alert the SPI master that it has data to

send. In turn, the SPI master needs to assert the GPIO connected to the SPWF04S chip

select and to start the CLK signal to send data to the slave.