| ??? 04/02/07 17:20 Read: times |
#136428 - For virtual COM port, USB-serial chips are better Responding to: ???'s previous message |
SiLabs also provide a virtual COM port driver, don't they? No. They provide a VCP (Virtual COM Port) driver for their USB-serial chips (CP210x), but they don't supply it for their USB MCUs ('F32x/34x). involves a device driver development on the PC, the most terrible work. Doesn't the SiLabs USBXpress stuff cover this? VCP is realized by a device driver on PC. Windows have a built-in device driver, usbser.sys, for this purpose. Most of VCP examples from USB MCU manufacturers apply this device driver. However, the function of usbser.sys is limited comparing to the USB-serial chips from FTDI, SiLabs, etc. For example, usbser.sys doesn't support CTS; EscapeCommFunction() (Win API) doesn't change RTS, etc. Please see the details on this post on SiLabs forum. "USB CDC implementation for 'F32x" E) Weird usbser.sys http://www.cygnal.org/ubb/Forum9/HTML/000945.html SiLabs USBXpress provides 'direct' ports, instead of VCP. To use these ports on your PC app, the PC app should be rewritten to access these ports. As they aren't customized for UART signals, you have to make a handler to carry entire UART signals, TX/RX data stream and handshake signalings. When you elaborate on it, you may support more than single UARTs. It can, but much more troublesome than USB-serial chips. If your requirement is VCP, dedicated USB-serial chips are far better than USB MCUs. Tsuneo |
