
EM358x
124
Rev. 0.4
9 USB Device
9.1 Overview
The EM3582, EM3586, and EM3588 have a USB 2.0-compliant full-speed (12 Mbps) device peripheral, with on-
chip transceiver. Other EM358x variants (EM3581, EM3585, and EM3587) do not support USB.
The EM358x only supports one configuration (configuration 0) and two interfaces. By default all logical endpoints
are on the first interface (interface 0), while the USB_INTF1SEL register enables associating logical endpoints
with interface 1.
The EM358x supports up to six endpoints (in addition to the control endpoint 0). There are five endpoints that can
be used as either interrupt or bulk and one isochronous endpoint.
The USB peripheral is interfaced to the CPU through memory mapped registers for control, and DMA for data.
The USB device generates its own 48 MHz internal clock from the main 24 MHz crystal clock.
The EM358x fully supports USB suspend and resume modes, and can meet the USB specification suspend
current of <2.5 mA. It achieves this by switching the chip to run from a divided down version of the system clock.
Note:
Fully supporting all of electrical compliance for the purpose of an EM358x device passing USB Certification
is tightly coupled with the application being run on the EM358x and the larger system using the EM358x.
From the perspective of the EM358x device, suspend is an asynchronous event. Application designs will
have to change to effectively handle suspend, resume, remote wakeup and their clocking requirements.
Note:
The device is USB 2.0 compliant but only supports full-speed (12 Mbps).
9.2 Host Drivers
The goal of the USB COM port functionality Silicon Labs provides is to make it simple for an EM358x to interact
with a PC without needing a physical UART / RS-232 but still use the basic application serial functionality that has
been available on a UART.
There are two options for host drivers:
The Silicon Labs supplied driver: There is an “EM358VPInstaller” available for both x64 and x86
Windows. The device driver is signed and certified by Microsoft Windows Hardware Compatibility.
The Windows PC USB built-in driver: Silicon Labs provides the only Windows file that is necessary to use
the communications device class (CDC). This is a .inf file needed to allow Windows to recognize the
device correctly and load the built-in driver.
Once the driver is installed and the EM358x is connected to the computer via USB, nothing more is needed on
the host to configure this new COM port device.
9.3 Normal Serial COM Port Operation
From the perspective of the software developer, in addition to the existing serial port 1 - the UART – the use of
USB allows for the serial port 3 - the USB COM port. Port 1 and Port 3 will not affect each other. The majority of
the basic functionality available for the UART exists for the USB COM port. This includes the emberSerialPrintf()
and companion printing functions as well as emberSerialReadLine() and companion reading functions. Some of
the UART-style functionality, such as hardware flow control, is not available on the USB COM port.
9.4 References
The Original USB 2.0 specification released on April 27, 2000 is available from the USB Implementers Forum
(USB-IF) at:
http://www.usb.org/developers/docs/
The zip file
http://www.usb.org/developers/docs/usb_20_070113.zip
has the original specification along with
supporting information.
The information for testing a full-speed peripheral device can be found on the USB-IF Compliance Program page
at:
http://www.usb.org/developers/compliance/
Compliance test requirements are found at:
http://www.usb.org/developers/compliance/peripheral_low/
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