Datasheet
4D SYSTEMS SOMO-II
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SOMO-II Embedded Audio-Sound Module
5. Operating Modes
The SOMO module offers two modes of operation, SERIAL-MODE and KEY-MODE. This section describes both
modes in detail.
SERIAL MODE 5.1.
The SERIAL-MODE provides a simple 2-wire TTL Serial UART interface to any micro-controller capable of
interfacing to a 3.3V or 5.0V (See Section 4.1) TLL Serial UART system that can be configured to output the
simple protocol required to communicate with the SOMO-II.
Baud Rate: 9600 bps
Data bits: 1
Parity bit: none
Flow Control: none
The SOMO audio operations such as PLAY, PAUSE, STOP, NEXT, PREVIOUS and VOLUME etc are all available to
the host micro-controller to control using a simple set of bytes sent to the SOMO-II, along with many more,
which can be found under the Valid Commands listed below.
Command Format:
The format of the serial commands are as follows
FORMAT: $S, CMD, Feedback, Para1, Para2, Checksum1, Checksum2, $0
$S
Start Character $S is 0x7E in HEX
Every command starts with this
CMD
Command Code
Every command has a unique command
code, which determines the operation
Feedback
Command Feedback
Specifies whether feedback is required by
the host microcontroller in reply to the
command. 1 = Feedback, 0 = No Feedback
Para1
Parameter #1
First parameter of the specific Command
Code
Para2
Parameter #2
Second parameter of the specific Command
Code
Checksum1
Checksum #1
First byte of the checksum. Checksum
calculation shown below.
Checksum2
Checksum #2
Second byte of the checksum. Checksum
calculation shown below.
$0
End Character $0 is 0xEF in HEX
Every command ends with this
Checksum Calculation:
The checksum is calculated using the following formula.
Checksum (2 bytes) = 0xFFFF – (CMD + Feedback + Para1 + Para2) + 1
Valid Commands:
All commands shown below have Feedback turned off so there will be no data sent from the SOMO-II after the
command has been sent from the microcontroller (except for the Query commands which are requesting
data).