SM-B79
SM-B79 User Manual - Rev. First Edition: 1.0 - Last Edition: 1.0 - Author: A.R - Reviewed by M.B. - Copyright © 2021 SECO S.p.A.
58
3.3.16
USB Connectors
According to SMARC
®
Rel. 2.1.1 specification, SMARC
®
modules can have up to 2x USB 3.0 ports + 4x USB 2.0 only ports or 6x USB2.0 ports.
USB#0 and USB#3 ports can also have, optionally, the OTG / client capability.
Considering these possibilities, SM-B79 carrier board offers:
-
USB 2.0 port #0, which could be able to manage OTG functionality, is carried to USB micro-AB connector CN30 (described below);
-
USB 2.0 port #1 is carried to standard USB 2.0 Type-A Slot CN50 (described below);
-
USB 3.0 port #2 is carried to standard USB 3.0 Type-A slot CN72 (described below);
-
USB 3.1 port #3, which could be able to manage OTG functionality, is carried to USB Type-C connector CN9 (described below);
-
USB 2.0 port #4 is available on M.2 Key E slot CN36 (par.3.3.12);
-
USB 2.0 port #5 is available on M.2 Key B slot CN38 (par.3.3.13).
For all USB ports described below, common mode chokes are placed on all USB differential pairs for EMI compliance.
For ESD protection, on all data and voltage lines are placed clamping diodes for voltage transient suppression.
According to SMARC
®
Rel. 2.1.1 specification, USB Port #0, coming out from SMARC
®
module,
could support OTG functionalities (it depends on the functionalities offered by the SMARC
®
module
used, however).
For this reason, this port is carried out through a standard micro-AB connector, type Hirose p/n ZX62-AB 5PA(11),
described in the table on the left.
Depending on the support offered by the SMARC
®
module, and from the needed use of the system, it is necessary to
connect micro-A or micro-B USB cables to connector CN30.
A micro-A USB cable has to be used when the system has to work in Host mode. In this case, +5V_USB0_VBUS is a
power output of SM-B79 Carrier Board for the connected device.
When a micro-B USB cable is used, its USB0_OTG_ID pin is floating; this way, the board acknowledges that it must
configure itself to work as a Client. In this case, +5V_USB0_VBUS is an input power for the carrier board from the external Host.
Signal description of this port:
U/USB0_OTG-: SMARC
®
Module USB Port #0 differential pair
+5V_USB0_VBUS: USB voltage rail. It is an input for USB port working in Client mode, an output for Host mode and in this case the power rail is derived by +5V_ALW
with a dedicated 600 mA current-limited power switch IC
USB_ID: Client/Host identification signal. This signal is high when the USB port works in client mode, is low when works in Host mode.
Micro-AB USB Connector CN30
Pin
Signal
1
+5V_USB0_VBUS
2
USB0_OTG-
3
U
4
USB0_OTG_ID
5
GND