Communications Document

6 Introduction
1.2 Communications Interfaces
The following table outlines the various communications interfaces found on Morningstar prod-
ucts. (Each dot represents one interface.)
Product RJ-11 RS-232 EIA-485 Ethernet
PC MeterBus Adapter (MSC)
● ●
RS-232 / RS-485 Adapter (RSC-1)
● ●
Meter Hub (HUB-1)
● ● ● ● ● ●
Relay Driver (RD-1)
● ● ●
Remote Meter (RM-1)
●
TriStar Meter (TS-M / TS-M-2)
● ●
TriStar Remote Meter (TS-RM / TS-RM-2)
● ●
SunSaver Duo (SSD-25)
●
SunSaver MPPT (SS-MPPT-15L)
●
TriStar (TS-xx)
● ●
TriStar MPPT (TS-MPPT-xx)
● ●* ●* ●
SureSine (SI-300-xxxV)
●
Table 1. Morningstar Device Communication Interfaces
*RS-232 and EIA-485 connections share the same internal hardware, therefore, only one interface can
be used at a given time.
1.3 RS-232 vs. USB
Morningstar products use the RS-232 interface as standard for communication with a PC. Some
have inquired as to why a USB interface was not used instead. The following describes some of
the problems with USB and why RS-232 was chosen to be the Morningstar standard:
RS-232 is a more universal standard•
USB cannot go long distances (maximum range without repeaters/hubs is 5 meters)•
USB cannot communicate peer-to-peer•
USB requires more expensive hardware•
USB requires more software / RS-232 requires no driver support•
USB isn’t easily opto-isolated (opto-isolation helps protect devices from transient power •
surges)
USB is less popular as an industrial standard•
Ethernet has emerged as the more useful interface than USB, therefore, many new Morningstar
products will have a built-in Ethernet interface.