
Gemini Users Manual 127
8.7 Encoder Port
The Gemini encoder port is compatible with the “Y” cable typically used with many
encoders such the Losmandy DSCs or NGC Max. If you are using such a system, you
should just be able to plug your encoders in and enable them via Gemini’s menu. The
pinout information above will be useful however, if you are building your own encoders
or cables.
Over the years, only a small percentage of Gemini users connected axis encoders. Axis
encoders are now set offline by default. The 4 digital (TTL) inputs bits can be used
alternatively to connect to custom hardware such as limit switches or other devices. Their
state can be read using the extended serial line protocol (Gemini native command 312).
By utilizing these 4 bits for end switches, you can further customize your Gemini for
fully unattended operation.
Line 1 is the LSB, line 4 the MSB for the serial line command 312.
The four lines connect directly to the CPU's digital I/O pins and have weak pullups.
Electrically, they are 5V TTL compatible. If you attach a custom device to the encoder
port, it should actively drive the lines high when needed rather than relying on the
internal CPU pullups.
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