3.4.6.2 M.2 Wireless Interface

The board features one M.2 interface for connecting compatible wireless add-on cards.

Only wireless cards compatible with the PCIe M.2 Key E slot (J11) are supported.

The main interface integrated in the M.2 slot is SDMMC2, for the WiFi component of the add-on card. An optional SPI interface is also multiplexed with the SDMMC2 pins and is available by changing the JP5 jumper position on the J12 header.

The M.2 slot also features a UART interface with hardware flow control for the Bluetooth component of the add-on card.

An external 32.768-kHz oscillator provides the 32.768-kHz clock.

Other miscellaneous signals are present for reset, host interrupts and wake-up, device wake-up, TWI and PTA.

Power is ensured by the auxiliary 3.3V supply (U1).

The MODE select header J13, near the J11 slot, is reserved for future use.

Figure 3-37. M.2 Wireless Interface Connector Schematic

Table 3-22. M.2 Wireless Interface Connector Signal Description
PIO	Signal Name	Signal Description
PC28	SDMMC2_CK_PC28	SDMMC2 Clock signal
PC27	SDMMC2_CMD_PC27	SDMMC2 command line
PD20	WIFI_RSTN_PD20	M.2 device reset line
PC29	SDMMC2_DAT0_PC29	SDMMC2 data line 0
PC30	SDMMC2_DAT1_PC30	SDMMC2 data line 1
PC31	SDMMC2_DAT2_PC31	SDMMC2 data line 2
PD0	SDMMC2_DAT3_PD0	SDMMC2 data line 3
PC7	WIFI_TWD_PC7	M.2 device TWI Data signal
PC6	WIFI_TWCK_PC6	M.2 device TWI Clock signal
PD4	WIFI_WAKE_HOST_PD4	M.2 host Wake-up signal
PD1	WIFI_IRQN_PD1	M.2 device interrupt line
PD2	WIFI_TWI_IRQ_PD2	M.2 TWI host interrupt line
PD7	BT_TXD_PD7	Bluetooth UART Transmit Data signal
PD6	BT_RXD_PD6	Bluetooth UART Receive Data signal
PD5	BT_CTS_PD5	Bluetooth UART Clear to Send signal
PD3	BT_RTS_PD3	Bluetooth UART Ready to Send signal
PC27	WIFI_SPI_MOSI_PC27	M.2 device serial data input
PC28	WIFI_SPI_MISO_PC28	M.2 device serial data output
PC29	WIFI_SPI_SCK_PC29	M.2 device serial Clock signal
PIOBU0	PIOBU0_WAKE	M.2 host back-up Wake-up signal