How to best make use of a 100 LED, RS232 Breakout Box (for <100LEDs read Tech.tip 3).

The 100 LED BOB offer test circuits for all lines on both sides of the breakout panel: use this feature and start with open switches. Use the cable the you plan to use, or is used, in the installation. This cable can course, or already has solved, certain problems.

Step 1:      OPEN ALL SWITCHES and insert the BOB in the to be tested circuit.

The LEDs tell if you are dealing with matching interfaces (DTE-DCE) or interfaces of the same type. LEDs lighting on different lines mean matching interfaces. LEDs lighting on the same lines mean interfaces of the same type. Check for strange or missing signals.

Step 2:       Test GPD if both units are using different wall outlet.

This test is seldom made, GPD changes. Today the GPD level does maybe not cause a communication problem, tomorrow (or in months) is stops your system. 

All switches open allow for a GPD test between the right and left pins # 7 on the breakout panel. You can do this with a DVM, our BOBs have build-in circuitry to test GPD. GPD is coming from the electric distribution system. Tech.Tip # 4 explains GPD more in detail. 

Testing GPD in an early stage can safe you many trouble later.

Step 3:        Close switch # 7 (Signal Ground).

Knowing with which kind of interfaces you are dealing with you have to cross patch our can "just close switches". Work line by line, connecting control lines often must bring the right response from the other side (RTS is answered by CTS).

Control lines often require strapping. Watch out: if you are using an unknown cable, the side not connected to the BOB might have straps which do not show.