readme.txt

usb cdc 类(AVR MCU 实现 CDC)

                                    CDC-IO


    This is the Readme file to firmware-only CDC driver for Atmel AVR
    microcontrollers. For more information please visit
    http://www.recursion.jp/project/cdcio/


SUMMARY
=======
    The CDC-IO performs the CDC (Communication Device Class) connection over
    low-speed USB. It provides the parallel port interface without installing
    dedicated driver.
    The CDC-IO is developed by Osamu Tamura @ Recursion Co., Ltd.


SPECIFICATION
=============
    Send text command to read/modify port bits. Use any terminal software
    or your own program.

    CDC-IO parallel port: 18 bits
        PORTB: bit 0-5
        PORTC: bit 0-5
        PORTD: bit 0,1,4-7

    CDC-IO terminal settings
        speed: any
        datasize: 7/8 bit
        parity: any
        stopbit: any

      Although RS-232C setting is not matter, set data size to 8bit to avoid
      unexpected troubles. To see the requested command, turn on "local echo".

    CDC-IO command
        function       command       format         response
        -------------------------------------------------------
        Get            ?             addr ?         data, CR-LF
        Set            =             data addr =    CR-LF
        AND & Set      &             data addr &    CR-LF
	OR & Set       |             data addr |    CR-LF
        EX-OR & Set    ^             data addr ^    CR-LF

	addr:      memory mapped I/O address in hex
	data:      8 bit data in hex
        delimiter: Tab, Space, CR, LF

        predefined addr: (case-insensitive)
            PINB, DDRB, PORTB
            PINC, DDRC, PORTC
            PIND, DDRD, PORTD

        example:
          DDRB ? (+delimiter)      Replies DDRB value with CR-LF.
          12 34 = (+delimiter)     Write 0x12 to address:0x34, replies CR-LF.
          FB PORTC & (+delimiter)  Write (PORTC & 0xFB) to PORTC, replies CR-LF.

    Previous data and addr can be reused. Just enter command char to repeat.

    USB line is connected to PORTD2,3. Avoid changing these bits.
    Modify other DDRD bits using '&', '|' or '^'.
    If PORTD is assigned to output, use PIND to toggle bits.

    USB bus-powered Vcc is about 3.6V. Be careful of interfacing to the higher
    voltage circuit. Usable bus-powered current is about 80mA.

    Any SFRs(special function registers) are accessible. See AVR datasheet to
    use Timers, ADC, etc. 


    Although the CDC is supported by Windows XP/2000, Mac OS X,9.1, and Linux,
    CDC on low-speed USB is not allowed by the USB standard. Use CDC-IO at
    your own risk. 


USAGE
=====
    Build your circuit and write firmware (cdcio*.hex) into it.
    C1:104 means 0.1uF, R3:1K5 means 1.5K ohms.
    If the connection is unstable, add another diode after D2, or try other
    USB-Hub or PC.
    If you connect from your program written in VB, use kernel32.dll calls
    instead of Mscomm32.ocx.

    [Windows XP/2000]
    When you connect with a USB port first, a Driver Setup Dialog appears.
    Specify the folder in which "avrcdc.inf" exists, without searching
    automatically. Although it is warned that the driver is not certified,
    confirm it. It only loads Windows' built-in usbser.sys. Then, the Virtual
    COM port appears.
 
    [Mac OS X]
    You'll see the device /dev/cu.usbmodem***.

    [Linux]
    The device will be /dev/ttyACM*.
    Kernel 2.6 does not allow the low speed bulk transfer on UHCI host.
    uhci_q.c / usb_uhci.c must be modified to enable bulk transfer.


DEVELOPMENT
===========
    This driver has been developed on AVR Studio 4.13 and WinAVR 20070122.
    If you couldn't invoke the project from cdcio.aps, create new GCC project
    named "cdcio" under "cdcio****-**-**/" without creating initial file. 
    Select each Makefile at "Configuration Options".

    The code size of CDC-IO is 2.8KB, and 128B RAM is required at least.

    Fuses to be checked
        [RSTDISBL=1] (ATtiny only)
        [WDTON=0]
        [BODLEVEL=101]
        [CKSEL=1110 SUT=11]
      (use 0xFF 0xCE 0xFE for ATmega48)


USING CDC-IO FOR FREE
======================
    The CDC-IO is published under an Open Source compliant license.
    See the file "License.txt" for details.

    You may use this driver in a form as it is. However, if you want to
    distribute a system with your vendor name, modify these files and recompile
    them;
        1. Vendor String in usbconfig.h
        2. COMPANY and MFGNAME strings in avrcdc.inf  



    Osamu Tamura @ Recursion Co., Ltd.
    http://www.recursion.jp/project/cdcio/
    12 January 2007
    7 April 2007