Data Sheet

4D SYSTEMS SOMO-II
© 2014 4D SYSTEMS Page 5 of 17 www.4dsystems.com.au
SOMO
-II Embedded Audio
-Sound Module
4. Pin Description
This section describes in detail the hardware
interface pins of the SOMO-II.
Micro-controller Interface Pins
RX pin 11 (TTL Serial UART Receive):
This is the 3.3V TTL Serial UART Receive pin,
compatible with 3.3V TTL level Logic, designed to
be connected directly with a microcontroller or
other TTL capable UART controller. Used in
conjunction with the TX pin, the SOMO-II can be
controlled using SERIAL-MODE by sending
commands from the microcontroller rather than
having to wire on any external buttons direct to
the SOMO-II itself. Please refer to the SERIAL-
MODE section for information about the
commands.
TX pin 12 (TTL Serial UART Transmit):
This is the 3.3V TTL Serial UART Transmit pin,
compatible with 3.3V TTL level Logic, designed to
be connected directly with a microcontroller or
other TTL capable UART controller. Used in
conjunction with the RX pin, the SOMO-II can be
controlled using SERIAL-MODE by sending
commands from the microcontroller rather than
having to wire on any external buttons direct to
the SOMO-II itself. Please refer to the SERIAL-
MODE section for information about the
commands.
NOTE: For 5V systems, connect a series resistor
(1K Ohms) on the RX line of the SOMO-II to the TX
of the 5V micro-controller.
Key Interface Pins (Not ADKEYs)
NEXT/VOL+ pin 3 (Next Track/Volume up):
Selects the Next Audio file from the micro-SD
memory card or USB Flash drive (whichever is
selected) when the pin is connected to GND
momentarily. If the pin is held to GND then the
Audio volume is ramped up. Active LOW triggered
input. Connect this pin to a push-button in stand-
alone KEY-MODE.
PREV/VOL- pin 4 (Previous Track/Volume down):
Selects the Previous Audio file from the micro-SD
memory card or USB Flash drive (whichever is
selected) when the pin is connected to GND
momentarily. If the pin is held to GND then the
Audio volume is ramped down. Active LOW
triggered input. Connect this pin to a push-button
in stand-alone KEY-MODE.
Key Interface Pins (ADKEY’s)
ADKEY1, ADKEY2, pins 5, 6 (Array Keys):
These pins provide a method to connect 10 push
buttons up to each pin (up to 20 buttons total), to
enable broad functionality of the SOMO-II without
requiring the use of SERIAL-MODE.
Audio Output and Control Pins
SPK+, SPK- pins 15, 16 (Mono Speaker output):
These pins provide a differential amplified output
to a single speaker. Connect these pins to a
4/8/16/32ohm speaker, at a max of 3 Watts when
powered from a 5V Supply. 8ohm 2.5W is
recommended.
DAC_R, DAC_L pins 13, 14 (Stereo DAC output):
These are the Left and Right audio outputs,
capable of driving headphones directly or small
speakers, or fed into an external amplifier.
BUSY pin 8 (Playing Indicator output):
Playing Indicator, this pin shows if an audio file is
currently being played (Low Output), or if no audio
playback is currently occurring (High Output). The
SOMO-II features an LED indicator on board which
is connected to this pin, however it can also be
connected to an external amplifier enable circuit,
to disable the external amplifier when an audio file
is not being played.
It can also be used to signal the host micro the end
of the audio file in SERIAL-MODE, if required.
System Pins
GND pins 7, 10 (Module Ground):
Module ground pins. One of more of these pins
must be connected to ground.
VCC pin 9 (Module Supply Voltage Input):
Module supply voltage input pin. This pin must be
connected to a regulated supply voltage in the
range of 3.3 to 5.0 Volts DC. Nominal operating
voltage is 4.3 Volts.
USB+, USB- pins 1,2 (USB for Flash Drive):
These pins provide a USB 2.0 interface to an
external USB connector, to enable a USB Flash
drive to be connected to the SOMO-II as a media
source for MP3 audio files.