RS232 Troubleshooting for the Geminis

Related FAQs:  

• VIDEO: express basics training: GV or GT drive amplifiers 

• VIDEO: express basics training: GV6 or GT6 drive controllers 

• VIDEO: express basics training: GV6K or GT6K drive controllers 

• VIDEO: How to troubleshoot RS232 serial communications 

Each intelligence level of the Gemini family has different RS232 protocol abilites.

The GV & GT are Binary-only on units. They do not communicate via ASCII like most of Parker's other controllers. They require a translator which is done by the Communications Server (Com6srvr) that Motion Planner uses. The Com6srvr is an ActiveX component that may be used in other software like VB, VC++, LabView, etc.

The GV6 & GT6 originally were released also with just Binary communication. The Com6srvr was also required for translation. It was the same translation as was needed for the GV/GT. An ASCII translator card was then added to the hardware of the GV6/GT6. Units with serial numbers of 02061700000 and higher have both Binary and ASCII capability.

The GV6K & GT6K have the same controller board as used in the 6K and therefore have ASCII only.

POSSIBLE COMMUNICATION ISSUES AND REMEDIES

ASCII vs Binary mode:

Since the GV/GT and GV6/GT6 were initially the same, the Com6srvr treated them the same way and only used Binary. When the ASCII ability was added to the GV6/GT6, the Com6srvr was modified to change back and forth. For backwards compatibility, it was set to default to Binary. This default has been changed a couple of times over various version of Motion Planner.

Whichever the default is can cause communication problems. Here is a typical scenario:
The unit is not powered up or the RS232 cable is disconnected. Then Motion Planner powers up, tries to communicate, fails, and then sets its communication protocol to the default. If the unit is a GV/GT, which is binary-only, and Motion Planner defaults to ASCII, then communication will not work until Motion Planner is changed back to Binary via the ASCII command (1 = ASCII; 0 = Binary). If the unit is a GV6/GT6, which default to ASCII when shipped from the factory, and Motion Planner defaults to Binary, then communication will not work until Motion Planner is changed back to ASCII.

Motion Planner versions later than 4.3.1 add the functionality so that the communication protocol defaults properly depending on whether GV/GT or GV6/GT6 are selected.

24VDC "KEEP ALIVE:"

The "Keep Alive" in the GV6K and GT6K units is not optional. This 24VDC is required for logic power and therefore to communicate.

Check the serial cable:

1. Check your cable to make sure it has pinouts for a Null Modem RS232 cable (if you are using RS232). These pinouts are... Parker's part number is 71-016939-10 for a CE rated RS232 cable and is a 9-pin female connector on both ends.

2. Is the computer power cord and Gemini's power cord plugged into the same AC outlet? In some cases, a ground potential between two AC outlets has caused an RS232 port failure. Plug both into the same AC outlet. Try communicating with the other COM port, if the device has one. If you are using a laptop, unplug the AC power adapter.

3. If you are using Parker's RS232 cable, make sure the end labeled with the "No Connect" sticker is plugged into the Gemini instead of the computer. The cable should work both ways, but voltage potentials and noise can cause intermittent communication problems.

If you are in ASCII mode and can't see what you are typing:

Perform a Loop-back test. NOTE: This test works if a unit is in ASCII, but not if it is in Binary mode.

Disconnect the RS232 cable from the Gemini keeping it connected to the PC. Jumper pins 2 and 3 on the end of the cable together. If you can see what you are typing, then the RX and TX wires are good.