Try powering the Uno using an external power supply. Perhaps the IMU needs more current. The following is from the arduino.cc docs at https://store.arduino.cc/usa/arduino-uno-rev3.
The Arduino Uno board can be powered via the USB connection or
with an external power supply. The power source is selected
automatically.
External (non-USB) power can come either from an AC-to-DC adapter
(wall-wart) or battery. The adapter can be connected by plugging a
2.1mm center-positive plug into the board's power jack. Leads from a
battery can be inserted in the GND and Vin pin headers of the POWER
connector.
The board can operate on an external supply from 6 to 20 volts. If
supplied with less than 7V, however, the 5V pin may supply less than
five volts and the board may become unstable. If using more than 12V,
the voltage regulator may overheat and damage the board. The
recommended range is 7 to 12 volts.
By the way, I think modern genuine Arduino USB serial are CDC ACM. Clone board frequently use cheaper alternatives such as CP2104 or CH340 neither of which are usable with the USB host shield. So if you have another Uno, it should work plugged into the USB host shield using the CDC ACM driver. Some very old Arduinos uses FTDI instead.
As for FTDI, I have used the Adafruit FTDI breakout boards. Many companies make similar ones. Shorting Tx and Rx on the board should allow for easy testing. Data send from the USB host shield should be echoed back.
This was meant just for testing. To see if I can get the CDC drivers on the library to work for me. Now I know to try ACM, instead of one of the others. The library drivers all work for me except the CDC_FTDI, and now I will see if the ACM is also giving me problems.
I am considering just skipping the shield if I can get approval to do so. Would using this Micro USB to Serial/SPI/I2C converter(Adafruit FT232H Breakout - General Purpose USB to GPIO, SPI, I2C [USB C & Stemma QT] : ID 2264 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits) combined with a Micro male USB to Female USB connector (https://www.amazon.com/Rankie-Female-Adapter-Convertor-3-Pack/dp/B00YOX4JU6) work well? Simply hook it in and take Serial off of it through TX and RX with a Lenonardo or Mega. That or I2C/SPI with the UNO. I could also probably find a simpler/cheaper converter for just USB to Serial if I wished.
I mentioned a BeagleBone, although I know this forum is about Arduinos I am also considering connecting the male header coming out of the IMU into a Female to Female USB (https://www.amazon.com/DTOL-Type-Female-Adapter-USB_F-USB_F/dp/B000GHXTA0) and then taking a Male USB to TTL and hooking it into the beagle bone black. Several tutorials for getting Serial data from your PC uses a similar method, and so I think it would work.
I was curious what your thoughts were on these other options.
Try powering the Uno using an external power supply. Perhaps the IMU needs more current. The following is from the arduino.cc docs at https://store.arduino.cc/usa/arduino-uno-rev3.
I have it plugged into an external power supply. The sparkfun board will not connect properly otherwise. The power supplies output is 9 volts at 650mA. I could up that to 12 volts I guess, but the IMU is suppose to be functional at this amount of voltage/current.
I have no idea if the other USB serial devices will work. I have never used a beagle board. I doubt 12V vs. 9V will make a difference. 9V is more than enough to generate 5V.
The cdcftdi driver looks for the USB vendor ID=0x0403 and product ID=0x6001. Have you verified this matches the IMU?
If not, the product ID can be specified as the third paramter on the constructor. Windows device manager should show the IDs.
FTDI Ftdi(&Usb, &FtdiAsync, 0x60xx);
The cdcftdi driver looks for the USB vendor ID=0x0403 and product ID=0x6001. Have you verified this matches the IMU?
That worked! I am able to see data flow. Its not exactly what I expect from the low level communication guide, but I can work on that and see whats happening.
Thank you so much for your help!