Readme.txt 7.7 KB

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  1. This is the Readme file to Objective Development's firmware-only USB driver
  2. for Atmel AVR microcontrollers. For more information please visit
  3. http://www.obdev.at/vusb/
  4. This directory contains the USB firmware only. Copy it as-is to your own
  5. project and add all .c and .S files to your project (these files are marked
  6. with an asterisk in the list below). Then copy usbconfig-prototype.h as
  7. usbconfig.h to your project and edit it according to your configuration.
  8. TECHNICAL DOCUMENTATION
  9. =======================
  10. The technical documentation (API) for the firmware driver is contained in the
  11. file "usbdrv.h". Please read all of it carefully! Configuration options are
  12. documented in "usbconfig-prototype.h".
  13. The driver consists of the following files:
  14. Readme.txt ............. The file you are currently reading.
  15. Changelog.txt .......... Release notes for all versions of the driver.
  16. usbdrv.h ............... Driver interface definitions and technical docs.
  17. * usbdrv.c ............... High level language part of the driver. Link this
  18. module to your code!
  19. * usbdrvasm.S ............ Assembler part of the driver. This module is mostly
  20. a stub and includes one of the usbdrvasm*.S files
  21. depending on processor clock. Link this module to
  22. your code!
  23. usbdrvasm*.inc ......... Assembler routines for particular clock frequencies.
  24. Included by usbdrvasm.S, don't link it directly!
  25. asmcommon.inc .......... Common assembler routines. Included by
  26. usbdrvasm*.inc, don't link it directly!
  27. usbconfig-prototype.h .. Prototype for your own usbdrv.h file.
  28. * oddebug.c .............. Debug functions. Only used when DEBUG_LEVEL is
  29. defined to a value greater than 0. Link this module
  30. to your code!
  31. oddebug.h .............. Interface definitions of the debug module.
  32. usbportability.h ....... Header with compiler-dependent stuff.
  33. usbdrvasm.asm .......... Compatibility stub for IAR-C-compiler. Use this
  34. module instead of usbdrvasm.S when you assembler
  35. with IAR's tools.
  36. License.txt ............ Open Source license for this driver.
  37. CommercialLicense.txt .. Optional commercial license for this driver.
  38. USB-ID-FAQ.txt ......... General infos about USB Product- and Vendor-IDs.
  39. USB-IDs-for-free.txt ... List and terms of use for free shared PIDs.
  40. (*) ... These files should be linked to your project.
  41. CPU CORE CLOCK FREQUENCY
  42. ========================
  43. We supply assembler modules for clock frequencies of 12 MHz, 12.8 MHz, 15 MHz,
  44. 16 MHz, 16.5 MHz 18 MHz and 20 MHz. Other clock rates are not supported. The
  45. actual clock rate must be configured in usbdrv.h unless you use the default
  46. 12 MHz.
  47. 12 MHz Clock
  48. This is the traditional clock rate of V-USB because it's the lowest clock
  49. rate where the timing constraints of the USB spec can be met.
  50. 15 MHz Clock
  51. Similar to 12 MHz, but some NOPs inserted. On the other hand, the higher clock
  52. rate allows for some loops which make the resulting code size somewhat smaller
  53. than the 12 MHz version.
  54. 16 MHz Clock
  55. This clock rate has been added for users of the Arduino board and other
  56. ready-made boards which come with a fixed 16 MHz crystal. It's also an option
  57. if you need the slightly higher clock rate for performance reasons. Since
  58. 16 MHz is not divisible by the USB low speed bit clock of 1.5 MHz, the code
  59. is somewhat tricky and has to insert a leap cycle every third byte.
  60. 12.8 MHz and 16.5 MHz Clock
  61. The assembler modules for these clock rates differ from the other modules
  62. because they have been built for an RC oscillator with only 1% precision. The
  63. receiver code inserts leap cycles to compensate for clock deviations. 1% is
  64. also the precision which can be achieved by calibrating the internal RC
  65. oscillator of the AVR. Please note that only AVRs with internal 64 MHz PLL
  66. oscillator can reach 16.5 MHz with the RC oscillator. This includes the very
  67. popular ATTiny25, ATTiny45, ATTiny85 series as well as the ATTiny26. Almost
  68. all AVRs can reach 12.8 MHz, although this is outside the specified range.
  69. See the EasyLogger example at http://www.obdev.at/vusb/easylogger.html for
  70. code which calibrates the RC oscillator based on the USB frame clock.
  71. 18 MHz Clock
  72. This module is closer to the USB specification because it performs an on the
  73. fly CRC check for incoming packets. Packets with invalid checksum are
  74. discarded as required by the spec. If you also implement checks for data
  75. PID toggling on application level (see option USB_CFG_CHECK_DATA_TOGGLING
  76. in usbconfig.h for more info), this ensures data integrity. Due to the CRC
  77. tables and alignment requirements, this code is bigger than modules for other
  78. clock rates. To activate this module, you must define USB_CFG_CHECK_CRC to 1
  79. and USB_CFG_CLOCK_KHZ to 18000 in usbconfig.h.
  80. 20 MHz Clock
  81. This module is for people who won't do it with less than the maximum. Since
  82. 20 MHz is not divisible by the USB low speed bit clock of 1.5 MHz, the code
  83. uses similar tricks as the 16 MHz module to insert leap cycles.
  84. USB IDENTIFIERS
  85. ===============
  86. Every USB device needs a vendor- and a product-identifier (VID and PID). VIDs
  87. are obtained from usb.org for a price of 1,500 USD. Once you have a VID, you
  88. can assign PIDs at will.
  89. Since an entry level cost of 1,500 USD is too high for most small companies
  90. and hobbyists, we provide some VID/PID pairs for free. See the file
  91. USB-IDs-for-free.txt for details.
  92. Objective Development also has some license offerings which include product
  93. IDs. See http://www.obdev.at/vusb/ for details.
  94. DEVELOPMENT SYSTEM
  95. ==================
  96. This driver has been developed and optimized for the GNU compiler version 3
  97. (gcc 3). It does work well with gcc 4, but with bigger code size. We recommend
  98. that you use the GNU compiler suite because it is freely available. V-USB
  99. has also been ported to the IAR compiler and assembler. It has been tested
  100. with IAR 4.10B/W32 and 4.12A/W32 on an ATmega8 with the "small" and "tiny"
  101. memory model. Not every release is tested with IAR CC and the driver may
  102. therefore fail to compile with IAR. Please note that gcc is more efficient for
  103. usbdrv.c because this module has been deliberately optimized for gcc.
  104. USING V-USB FOR FREE
  105. ====================
  106. The AVR firmware driver is published under the GNU General Public License
  107. Version 2 (GPL2) and the GNU General Public License Version 3 (GPL3). It is
  108. your choice whether you apply the terms of version 2 or version 3.
  109. If you decide for the free GPL2 or GPL3, we STRONGLY ENCOURAGE you to do the
  110. following things IN ADDITION to the obligations from the GPL:
  111. (1) Publish your entire project on a web site and drop us a note with the URL.
  112. Use the form at http://www.obdev.at/vusb/feedback.html for your submission.
  113. If you don't have a web site, you can publish the project in obdev's
  114. documentation wiki at
  115. http://www.obdev.at/goto.php?t=vusb-wiki&p=hosted-projects.
  116. (2) Adhere to minimum publication standards. Please include AT LEAST:
  117. - a circuit diagram in PDF, PNG or GIF format
  118. - full source code for the host software
  119. - a Readme.txt file in ASCII format which describes the purpose of the
  120. project and what can be found in which directories and which files
  121. - a reference to http://www.obdev.at/vusb/
  122. (3) If you improve the driver firmware itself, please give us a free license
  123. to your modifications for our commercial license offerings.
  124. COMMERCIAL LICENSES FOR V-USB
  125. =============================
  126. If you don't want to publish your source code under the terms of the GPL,
  127. you can simply pay money for V-USB. As an additional benefit you get
  128. USB PIDs for free, reserved exclusively to you. See the file
  129. "CommercialLicense.txt" for details.