User's Manual
18 63-70-076-DOC-1 September 2013
User ManualMARS-24ATR
4.2.2 user i/o interfAce connector
The MARS-24ATR has an external interface connector called the USER I/O. This provides a number of digital I/O
points. These can be used under application control to connect to external devices such as buttons and lights.
The connector is a DB-15 pin female.
The pins are used as follows:
Pin Number Direction Function
1 Power 5V at up to 500mA
2 Power 3V3 at up to 200mA
3 GND Ground
4 SDA I2C Data Signal
5 I/O External I/O
6 I/O External I/O
7 I/O External I/O
8 I/O External I/O
9 Power 12V at up to 1.1A
10
GND Ground
11 SCL I2C Clock Signal
12
I/O External I/O
13
I/O External I/O
14
I/O External I/O
15
I/O External I/O
All the External output line pins can be controlled using the ExternalOutputState() and ExternalOutputPulse() API
commands using the number specied in the table. For example, ExternalOutputState(3,1) would turn on the output
on pin 9. Note that the outputs are intended to drive a simple LED indicator or provide a control signal to a more
powerful external buer. All outputs are 3.3V.
All the External input line pins will generate log messages when the state of a pin changes, for example Info,External:
Input 4 changed state to 0. The External input() API function can also be called to read the state of all inputs as a number.
The inputs allow connection to either switches or any external sensor which provides a contact closure or TTL compatible
signal.
When designing external hardware, we strongly advise checking the design with Magellan beforehand to verify that it
will be electrically compatible.