Communications Document

51Morningstar Product Connectivity Manual
Power must be applied as follows:
+ Power must be asserted on the DTR and/or RTS pins
- Power must be asserted on the RTS and/or RX pins
Modicationscanbemadetoyourequipment(orRS-232cable,butthisisusuallymoredifcult)
so that the correct power is delivered to the Morningstar unit. Internally wiring several pins is
usually all that is needed, but there is some equipment that does not provide negative (-) power
atall,onanypin.TheseproductscannotbemodiedtocommunicatewithMorningstarunitsvia
RS-232.
NOTE: The TriStar MPPT has pins 4 and 6 internally
connected, and pins 7 and 8 internally connected.
USB to Serial Problems
Be sure you have read Subsection 5.3 on Establishing A Connection with your morningstar de-
vice. A common problem is the use of a Virtual Com Port when using a USB to Serial connection.
This Subsection should rectify any VCOM problems that may exist.
If you are still having problems:
There have been reports that some USB to Serial adapters do not work with Morningstar prod-
ucts. This is most often because the adapter output voltage is below the RS-232 electrical speci-
cation.Iftheadapterdoesnotoutputahighenoughvoltage,thereislittletheusercandoto
remedy the situation aside from purchasing a new adapter with the proper output voltage levels.
The Tripp Lite U209-000-R adapter described in Subsection 2.2.8 has been veried to work
with all Morningstar products.
NOTE: RS-232 line boosters are available which
will amplify the signal voltage to the proper RS-232
specications. These can be found online or in most
electronics stores
Also, the number of USB devices connected to your PC may have an effect on communication
with your Morningstar controller/inverter. More USB devices connected to your PC, especially
through a USB hub, the greater the likelihood of timing problems on the bus. Because the MOD-
BUS
TM
protocol used to communicate between a PC and controller/inverter is very timing-depen-
dent, timing problems can cripple communication capabilities. Unplug some of your other USB
devices and attempt a connection again.
Connection Distance Limitations
The following table outlines the various maximum wire run distances between two devices using
the interfaces described in the rest of this manual. Different protocols have different timing and