SoM-250ES_User_Manual_v1.40.doc
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Rev 1.4 © 2014 EMAC, Inc.
2.5
USB Host Ports
The SoM-250 provides one dual USB 2.0 (USB Port A & B) high speed host port (JK3). USB PortA and PortB
can be accessed from the bulkhead connector (HDR5). EMAC can provide a cable (CAB-40-004) to access these
ports.
In addition to the one USB Host port, the SoM-250 provides a USB On-The-Go (OTG) port. This port can be used
as either a USB Host or USB Device port.
All of the USB ports are equipped with 500mA re-settable Polyfuses. If a USB Device tries to draw more than
500mA from the port, the fuse will open until the device is unplugged or its current requirement is reduced. There
is no software provision for shutting down power to the Ports or detecting when a port is drawing too much
current.
Note:
When sizing a power supply, make sure to allow for USB Device consumption. A device can potentially
draw 500mA, therefore these devices could use a total of up to 1 amp of power.
2.6
Audio Port
The SoM-250 provides Audio Line Out and Line In capability through two standard audio jacks (JK5 & JK6). Audio
Jack JK5 is stereo line level input and Audio Jack JK6 is stereo line level output. The processor interfaces to the
Audio CODEC through its I
2
S interface. Command control of the CODEC is done using the processor
’s SPI
interface. The CODEC is the Cirrus CS4271, which is a high performance 24-bit Stereo CODEC offering superior
sound quality.
Both the input and output are line level. You will probably not be able to drive an unamplified speaker although
standard headphones will work. Likewise, an un-amplified microphone probably will not work as an input although
the line out of a CD player will work.
2.7
LCD Brightness Control
The SoM-250 offers LCD brightness control that can change the brightness of the LCD via software. The LCD
utilizes LED backlighting. The board provides the backlight with approximately 10 volts at about 220mA. The
processor provides a PWM (SoM pin# 85) that is used to drive the LCD backlight. Changing the duty-cycle of the
PWM directly affects the brightness of the LCD. In addition, the backlight can be turned off or on via SoM port line
GPIO0 (SoM pin#114). This allows screensaver software to automatically turn off the backlight when the unit is
not being used and to automatically turn it back on when the touchscreen is touched.
2.8
MicroSD Card Socket
The SoM-250 provides a high capacity MicroSD socket. This socket is hot-swappable and can accept a wide
variety of Flash Cards. A green activity light (LED LD3) is located towards the left side of the socket. When the
processor is accessing the Flash card this LED will be lit and the card should not be removed at this time. A card
that is written to by the SoM-250 can be read by another computer using an MicroSD card reader. The MicroSD
interface is compatible with Standard and High Capacity MicroSD cards.
2.9
Keyboard/Mouse
The SoM-250 does not provide a PS/2 type keyboard/mouse interface. However, a USB keyboard and mouse
can be used if required.
2.10
Analog Inputs
The analog inputs are available on HDR1 (see table 5 below) and are labeled as analog_04, analog_05,
analog_06 and analog_07. These may or may not be supported by the SoM plugged into this carrier.
