Icom IC-9100 USB interface and WSJT-X under linux

First, downloaded the latest Beta WSJT-X for Ubuntu, Version 1.5-rc1.  Then plugged in the USB cable into my Ubuntu 15.04 desktop.  This produced three devices, one sound card and two serial ports.  Here a snip from the lsusb utility...

Bus 007 Device 017: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP210x UART Bridge / myAVR mySmartUSB light

Bus 007 Device 016: ID 08bb:2901 Texas Instruments PCM2901 Audio Codec

Bus 007 Device 015: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP210x UART Bridge / myAVR mySmartUSB light

The sound card has a different name in the WSJT-X setting display

alsa_input.usb-Burr-Brown_from_TI_USB_Audio_CODEC-00-CODEC.analog-stereo
alsa_output.usb-Burr-Brown_from_TI_USB_Audio_CODEC-00-CODEC.analog-stereo

Two new serial ports appeared ttyUSB0 and ttyUSB1.  Specifying /dev/ttyUSB0 in Settings made the CAT work right away

The sound card also worked right away.  But the level from the 9100 seems about 30 dB too high and the input level slider needs to be placed almost all the way to the bottom.

It took a while to get the USB Tx modulation working.  The 9100 has a setting to specify the source of modulation from the USB sound card. Settings number 58 and 59 set Data Off Modulation input and Data On Modulation input. Set both to USB.

WSJT-X can use either SSB or SSB Digital mode.  On the 9100, access digital mode with a long press on the SSB key, in WSJT-X it's controlled in settings.

By using Digital Mode, The Rx bandwidth can be set to 3.6 KHz and the passband tuners can shift the bandwidth up 300 Hz to cover most of the JT9 portion of the band.

It's not possible to extend the Tx bandwidth above 2.9 KHz, so WSJT-X uses the "fake it" mode to shift the Tx frequency to the best range.