Critical Link, LLC
www.CriticalLink.com
FEATURES
1 RS-232 Compliant Output
1 RS-232 Compliant Input
RS232 Protocol
-
Up to 115,200 baud rate
On-Board TX/RX Output Swapping
-
Resistor changeable
Compatible with MitySOM/MityDSP
based Development Kits from
Critical Link
RS232 Expansion Kit
5 March 2014
Applications
External Hardware Interfacing
Embedded Instrumentation
(1.8” x 1.2” – actual size)
DESCRIPTION
The RS232 Expansion Kit is compatible with Critical Link’s line of MitySOM/MityDSP
based development kits; one is required to interface with this expansion kit. All
MitySOM/MityDSP based System on Modules support RS232, see Table 1 for details
concerning SoM support.
Table 1: Critical Link SoM RS232 Support
Module Type
MitySOM-1810
MitySOM-1810F
MityDSP-L138
MityDSP-L138F
MitySOM-1808
MitySOM-1808F
MitySOM-3359
RS232 Support
Yes
Yes
Yes
Yes
Yes
Yes
Yes
1
Copyright © 2007-2012, Critical Link LLC
Critical Link, LLC
www.CriticalLink.com
RS232 Expansion Kit
5 March 2014
RS232 Description
The RS232 Expansion Kit provides standard serial interface at data rates up to 115,200
baud that can be seamlessly added to your design. The serial interface is routed to one of
the UART ports of the MitySOM/MityDSP through the UART Expansion Header on a
MitySOM/MityDSP based Development Kit.
Linux Driver and API examples are available.
The level conversion from the input CMOS levels to the output RS232 levels is done by a
MAX3232IDR Line Driver/Receiver. This part offers two receivers and drivers but the
second set is unused on this board.
Through the use of 4 resistors the RS232 Expansion Kit can alter which output pins are
used for TX and RX depending if a null-modem or standard cable type is necessary. See
Table 4 for details.
The electrical interface between the RS232 Expansion Kit and MitySOM/MityDSP based
Development Kit is provided via the 10-pin shrouded header described in Table 2.
The electrical interface between the RS232 Expansion Kit and an external device is
provided via the 9-pin DB9 connector described in Table 3.
Please reference your specific MitySOM/MityDSP Based Development Kit
documentation to determine which connector to use for the RS232 Expansion Kit.
2
Copyright © 2007-2012, Critical Link LLC
Critical Link, LLC
www.CriticalLink.com
RS232 Expansion Kit
5 March 2014
RS232 Expansion Kit Pinouts
Table 2 shows the input 10-pin shrouded header pin out for the RS232 Expansion Kit
input header. This connector, J501, is the interface to the MitySOM/MityDSP based
development kit.
Table 2: PROFIBUS/RS485 Expansion Kit 10-Pin Header Pin Out
Pin
1
2
3
4
5
6
7
8
9
10
Name
ENB
RXD
+3.3V
Reserved
Reserved
TXD
GND
Reserved
Reserved
Reserved
Type
3.3V CMOS
3.3V CMOS
Power
-
-
3.3V CMOS
Power
-
-
-
Note
Unused - Input to Expansion
Output from Expansion
20mA max
Input to Expansion
Table 3 shows the output 9-pin DB9 connector, J500, to interface with an outside RS232
device.
Table 3: RS232 Expansion Kit 9-Pin DB9 Pin Out
Pin
1
2
3
4
5
6
7
8
9
Name
Reserved
RS232_RX
RS232_TX
Reserved
GND
Reserved
Reserved
Reserved
Reserved
Type
-
RS232
RS232
-
Power
-
-
-
-
Note
Data signal - See Note 1 below
Data signal - See Note 1 below
Note 1:
The RX and TX output pins can be swapped on the expansion board by changing
R401/R403 and R400/R402 for RX and TX respectively, see schematic and Table 4 for
details.
Table 4: RS232 Output Resistor Settings
Output Pins
RX Pin 2 TX Pin 3
RX Pin 3 TX Pin 2
R400
-
Populated
R401
-
Populated
R402
Populated
-
R403
Populated
-
3
Copyright © 2007-2012, Critical Link LLC
Critical Link, LLC
www.CriticalLink.com
RS232 Expansion Kit
5 March 2014
ABSOLUTE MAXIMUM RATINGS
If Military/Aerospace specified cards are
required, please contact the Critical Link
Sales Office or unit Distributors for
availability and specifications.
Maximum Supply Voltage, Vcc
Storage Temperature Range
3.4 V
-65 to 80C
OPERATING CONDITIONS
Commercial
Temperature Range
Humidity
0 to 70C
0 to 95%
Non-condensing
ELECTRICAL CHARACTERISTICS
Symbol
Vcc
Icc
Parameter
Voltage supply, 3.3 volt input.
Quiescent Current draw, 3.3 volt input
Conditions
Min
Typ
3.3
TBD
Max
3.4
TBD
Units
Volts
Milliamps
4
Copyright © 2007-2012, Critical Link LLC
Critical Link, LLC
www.CriticalLink.com
ORDERING INFORMATION
RS232 Expansion Kit
5 March 2014
The following table lists the orderable module configurations. For shipping status,
availability, and lead time of these or other configurations please contact your Critical
Link representative.
The necessary 10-pin cable to connect to a MitySOM/MityDSP based Development Kit
is provided with each RS232 Expansion Kit.
Table 5: Orderable Model Numbers
Model
Protocol(s) Supported
80-000541
RS232
MECHANICAL INTERFACE
A mechanical outline of the RS232 Expansion Board is illustrated below.
Figure 1: Dimensions 1.8" x 1.2"
REVISION HISTORY
Date
10-OCT-2012
17-OCT-2012
5-MAR-2014
Change Description
Initial revision.
Update part number
Update MitySOM product name
5
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