Gemini Users Manual 82
negative power terminals should be connected with low resistance wire. Alternatively,
electrically isolated power supplies or batteries can be used.
6.1.2 Settings
Except when querying GPS units, Gemini’s serial port is set to communicate at 9600
baud (9600 bps), no parity, 8 data bits, 1 stop bit. You must configure the COM port of
the connected computer to match these settings. In addition, the handshake protocol
setting for the COM port should be set to “None” (neither hardware nor software
handshake). Most planetarium programs perform these settings automatically for you.
6.1.3 Troubleshooting Serial Communications
If you cannot communicate with the Gemini after checking the wiring, you can use
Gemini’s Debug Mode to find out if serial data is being received correctly. In this mode,
the commands received (without their numeric parameters) are stored in the Information
Buffer and can be displayed using the "Show Information" menu item.
At the PC side, any terminal emulation program such as HyperTerm under Windows, or
MiniCom under Linux can be used. Connect to the COM port after setting the
parameters as described above and type some commands from the serial command set
like :P#, :GR# or :GD# on the PC. Gemini should send characters in response.
If there is no response displayed, use Gemini’s “Show Information” command to check
whether or not Gemini received the commands sent. If not, try the following steps:
• Connect PC and Gemini with a minimum of cabling and hardware. Use a short
cable.
• Double-check the settings of the serial port.
• Make sure Gemini started up correctly and the startup process is finished
(otherwise most commands will not be recognized).
• Make sure no other program (planetarium program, ActiveSync,...) is accessing
the port.
• Make sure the port is not redirected to IrDA.
If Gemini is still not receiving commands, try different settings of the “Send Buffer
FIFO” in the Extended Settings for the COM port of the PC.
Once the commands reach Gemini, the response should be seen quickly. If not, try the
other possible settings of the Receive Buffer FIFO.
See also section 7.1.14.
6.2 Hand Controller port
There are two sockets available to connect a hand controller to Gemini: the modular RJ11
socket for the classic Losmandy hand controller and the DB15 sub-D socket to connect
the Deluxe Hand Controller to the Gemini board. From level 4 up, the DB15 port can also
be used alternatively as a second serial port. Since the serial pins connect directly to the
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