scrypt only mining, just use the version on github. Have a look the readme file to know how to build it for Linux. The dip switch is very important. It changes the voltage of electricity. To get higher scrypt mining performance, switch it to L. When the switch is on L. You can mine at 850Mhz. Otherwise, only 600Mhz or below be used.
From the above example I am using
cgminer.exe --scrypt --lo -o stratum+tcp://ltc.give-me-coins.com:3333 -u TomInVa57 -p 12 -S //./COM3 --dualminer-pll 850
the only thing that happens is the cgminer command window opens and immediately shuts down.. Switch is in LTC mode only.
NOTE: Pay attention to the device name in command line. There are two serial port devices appear if the VCP driver installed successfully. One for BTC nonce report, another for LTC nonce report.
For example, if you see COM3 and COM4, usually COM3 is BTC port, COM4 is LTC. In some rare case, COM4 is for BTC, COM3 is for LTC.
To do a LTC only mode mining(--lo is given), please give the BTC port as the device name. In this mode, the chip is configured to report LTC nonce to BTC port.
In dual mode, make sure BTC mining process uses BTC port, LTC mining process uses LTC port.