hello , i am very new to usb program,i just read only usb doc for stm32f103xx controller but i didnt get anything.could you please guide me how to learn usb virtual com port programm and what are the things we needto have(like hardware and softwares). i also dowloaded the virtual comport drivers but my board is not detecting. please try to help me.its very important to me thanks in advance
> could you please guide me how to learn usb virtual com port programm and what are the things we needto have(like hardware and softwares).
USB is a typical complicated protocol stack, protocols on protocols. It's hard to realize fully to the extent in which you can make your own stack. It takes almost half an year for me, until I have made my own stack confidently.
a) Your own USB stack If you follow this route, start with an existing example. Try to decipher the stack source code, first. Unfortunately, Keil doesn't provide any CDC (Communication Device Class: virtual COM port) example for STM32F103. Here is ST's.
STM32F10x, STM32L1xx and STM32F3xx USB full speed device library (UM0424) v4.0.0 www.st.com/.../stm32_usb-fs-device_lib.zip
These references are available to know USB protocols better.
USB Made Simple http://www.usbmadesimple.co.uk
USB in a NutShell www.beyondlogic.org/.../usb1.shtml
Jan Axelson's USB Central http://www.lvr.com/usb.htm
And her book: USB complete http://www.lvr.com/usbc.htm
USB 2.0 Specification www.usb.org/.../usb_20_110512.zip
CDC spec on USB.org www.usb.org/.../CDC1.2_WMC1.1_012011.zip
b) a user of existing USB stack Most of people take this option ;-) Even for these users, above references are helpful, when (s)he comes across a problem.
c) a user of USB-UART chips This is the easiest option. FTDI, SiLabs, Prolific sell such a chip.
Tsuneo