Appendix C – Connector Pin Assignments 
C.1 
 
C.1.1  GPIO Connector (37-Pin D-Sub) 
ESP300 Rear Panel 
This connector is dedicated to the digital I/O ports. All I/O are pulled 
up to +5V DC with 4.7KΩ resistors. Maximum sink or source current 
is 32 mA. Connector pin-outs are listed in 
Table C.1, and 
functionally described in the following paragraphs. 
C.1.2  Signal Descriptions (Digital I/O, 37-Pin, JP4 Connector) 
+15V supply 
Digital Ground used for all digital signals. 
+5V, 100mA (maximum) 
+5V supply 
+15V, 25mA (maximum) 
Digital I/O 
The digital I/O can be programmed to be either input or output (in 8-
bit blocks) via software. 
DGND 
Pin #  Description 
1 +15V, 25mA 
2 +15V, 25mA 
3 +5V, 100mA 
4  Digital Input/Output 1 
5  Digital Input/Output 2 
6  Digital Input/Output 3 
7  Digital Input/Output 4 
8  Digital Input/Output 5 
9  Digital Input/Output 6 
10  Digital Input/Output 7 
11  Digital Input/Output 8 
12  Digital Input/Output 9 
13  Digital Input/Output 10 
14  Digital Input/Output 11 
15  Digital Input/Output 12 
 
Table C.1: Digital Connector Pin-Outs 
Appendix C – Connector Pin Assignments  C-1