I was not able to get the difference after much googling.I am a newbie in microcontrollers and doing a project on Temperature controlled fan using LabVIEW and PIC18F4550. I need to know how communication takes place between the two. I also need to know that if USB 2.0 is a half-duplex system then how will I achieve real-time control of speed of the fan which depends on the temperature.How will the PIC be used a CDC or HID?

  • \$\begingroup\$ Between which two? CDC and HID? Or LabView and PIC (and fan)? CDC and HID classes have very little in common, I suggest to keep googling. USB is much faster than fan, for motor control applications you don't need to worry about low-level USB protocol details such as duplex. \$\endgroup\$ Feb 9, 2015 at 8:29
  • \$\begingroup\$ USB protocols have some defined latency (as any half-duplex system does). Frame rate for USB 2.0 is 1msec. How frequently does your system really need to make decisions about fan control? And why can't the control loop reside inside your PIC18F4550 firmware, instead of going through USB? \$\endgroup\$
    – MarkU
    Feb 9, 2015 at 8:40
  • \$\begingroup\$ The documentation of TI's MSP430 USB Developers Package explains this. \$\endgroup\$
    – CL.
    Feb 9, 2015 at 9:33


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