1 Introduction
M.2 is a form factor for mobile adapters defined by the PCI-SIG (http://
www.pcisig.com). The pinouts for M.2 sockets are defined in the PCI Express
M.2 Specification.
M.2 sockets with mechanical Key E are used on platforms based on NXP MPUs and MCUs to support wireless connectivity
modules based on NXP Wi-Fi/Bluetooth radios.
Some of the signals defined in the pinout are used to connect optional sideband and debug signals used by NXP Wi-Fi/
Bluetooth radios.
In order to ensure the proper connection for sideband and debug signals, this document defines the pin assignments for M.2
sockets (mechanical Key E) on platforms based on NXP MPUs and MCUs.
Before building your board, check the interface connector specification from the wireless module vendor to confirm the pinout used
by the module.
For the full definition of the socket pinout, refer to the
PCI Express M.2 Specification
, available from PCI-SIG website
(http://www.pcisig.com).
All the pins that are not listed in this document are recommended to follow the PCI Express M.2 Type E specification
or should
not be connected
.
NOTE
2 Sideband and debug signals
Table 1 shows the pin assignments utilized for sideband and debug signals.
Note: Check the module datasheet for details on mandatory and optional lines.
Table 1. Sideband and debug signals
Pin PCIe M.2
Signal
Type
1
Voltage NXP Usage Description
20 UART_WAKE# I 3.3 V BT_WAKE_HOST
Sideband signal used by the Bluetooth radio to
wake up the platform.
Active Low by default Connect to Host GPIO
Open drain. Pullup required on platform.
21 SDIO_WAKE# I 1.8 V WLAN_WAKE_HOST
Sideband signal used by the Wi-Fi radio to wake
up the platform.
Active Low by default Connect to Host GPIO
Open drain. Pullup required on platform.
Table continues on the next page...
Contents
1 Introduction......................................1
2 Sideband and debug signals...........1
3 Host and audio interfaces............... 3
4 Revision history...............................4
AN13049
Wi-Fi/Bluetooth M.2 Key E Pinout Definition
Rev. 2 — 16 September 2021
Application Note
Table 1. Sideband and debug signals (continued)
Pin PCIe M.2
Signal
Type
1
Voltage NXP Usage Description
23 SDIO_RESET
#
O 1.8 V WLAN_INDEPENDEN
T_ RESET
Sideband signal to independently reset the Wi-
Fi radio.
Active Low by default Connect to Host GPIO.
38 VENDOR
DEFINED
I/O 1.8 V JTAG_TDO
Used for debug.
Connect to JTAG header on platform.
40 VENDOR
DEFINED
O 1.8 V DEV_WLAN_WAKE /
COEX4
Sideband signal used by the platform to wake up
the Wi-Fi radio.
Active Low.
Connect to Host GPIO.
42 VENDOR
DEFINED
O 1.8 V DEV_BT_WAKE
Sideband signal used by the platform to wake up
the Bluetooth radio.
Radio Coexistence line 4.
Active Low.
Connect to Host GPIO.
44 COEX3 I/O 1.8 V JTAG_TDI / COEX3
Radio Coexistence line 3.
Used for debug.
Connect to JTAG header on platform.
46 COEX2 I/O 1.8 V JTAG TCK / COEX2
Radio Coexistence line 2.
Used for debug.
Connect to JTAG header on platform.
48 COEX1 I/O 1.8 V JTAG_TMS / COEX1
Radio Coexistence line 1.
Used for debug.
Connect to JTAG header on platform.
54 W_DISABLE2# O 3.3 V BT_INDEPENDENT_
RESET
Sideband signal to independently reset the
Bluetooth radio.
Active Low by default Connect to Host GPIO.
56 W_DISABLE1# O 3.3 V PDn
Full Power-down for the Wi-Fi/Bluetooth radio:
High = normal mode.
Low = full power-down mode Connect to
Host GPIO.
1. Type refers to the signal direction:
• Type O means signal is an output from the MPU/MCU to the adapter.
• Type I means signals is an input to the MPU/MCU from the adapter.
NXP Semiconductors
Sideband and debug signals
Wi-Fi/Bluetooth M.2 Key E Pinout Definition , Rev. 2, 16 September 2021
Application Note 2 / 5