1 | Version 2009-08-22
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2 |
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3 | ==========================
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4 | WHY DO WE NEED THESE IDs?
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5 | ==========================
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6 |
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7 | USB is more than a low level protocol for data transport. It also defines a
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8 | common set of requests which must be understood by all devices. And as part
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9 | of these common requests, the specification defines data structures, the
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10 | USB Descriptors, which are used to describe the properties of the device.
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11 |
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12 | From the perspective of an operating system, it is therefore possible to find
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13 | out basic properties of a device (such as e.g. the manufacturer and the name
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14 | of the device) without a device-specific driver. This is essential because
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15 | the operating system can choose a driver to load based on this information
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16 | (Plug-And-Play).
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17 |
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18 | Among the most important properties in the Device Descriptor are the USB
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19 | Vendor- and Product-ID. Both are 16 bit integers. The most simple form of
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20 | driver matching is based on these IDs. The driver announces the Vendor- and
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21 | Product-IDs of the devices it can handle and the operating system loads the
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22 | appropriate driver when the device is connected.
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23 |
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24 | It is obvious that this technique only works if the pair Vendor- plus
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25 | Product-ID is unique: Only devices which require the same driver can have the
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26 | same pair of IDs.
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27 |
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28 |
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29 | =====================================================
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30 | HOW DOES THE USB STANDARD ENSURE THAT IDs ARE UNIQUE?
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31 | =====================================================
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32 |
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33 | Since it is so important that USB IDs are unique, the USB Implementers Forum,
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34 | Inc. (usb.org) needs a way to enforce this legally. It is not forbidden by
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35 | law to build a device and assign it any random numbers as IDs. Usb.org
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36 | therefore needs an agreement to regulate the use of USB IDs. The agreement
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37 | binds only parties who agreed to it, of course. Everybody else is free to use
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38 | any numbers for their IDs.
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39 |
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40 | So how can usb.org ensure that every manufacturer of USB devices enters into
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41 | an agreement with them? They do it via trademark licensing. Usb.org has
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42 | registered the trademark "USB", all associated logos and related terms. If
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43 | you want to put an USB logo on your product or claim that it is USB
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44 | compliant, you must license these trademarks from usb.org. And this is where
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45 | you enter into an agreement. See the "USB-IF Trademark License Agreement and
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46 | Usage Guidelines for the USB-IF Logo" at
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47 | http://www.usb.org/developers/logo_license/.
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48 |
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49 | Licensing the USB trademarks requires that you buy a USB Vendor-ID from
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50 | usb.org (one-time fee of ca. 2,000 USD), that you become a member of usb.org
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51 | (yearly fee of ca. 4,000 USD) and that you meet all the technical
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52 | specifications from the USB spec.
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53 |
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54 | This means that most hobbyists and small companies will never be able to
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55 | become USB compliant, just because membership is so expensive. And you can't
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56 | be compliant with a driver based on V-USB anyway, because the AVR's port pins
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57 | don't meet the electrical specifications for USB. So, in principle, all
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58 | hobbyists and small companies are free to choose any random numbers for their
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59 | IDs. They have nothing to lose...
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60 |
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61 | There is one exception worth noting, though: If you use a sub-component which
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62 | implements USB, the vendor of the sub-components may guarantee USB
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63 | compliance. This might apply to some or all of FTDI's solutions.
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64 |
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65 |
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66 | =======================================================================
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67 | WHY SHOULD YOU OBTAIN USB IDs EVEN IF YOU DON'T LICENSE USB TRADEMARKS?
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68 | =======================================================================
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69 |
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70 | You have learned in the previous section that you are free to choose any
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71 | numbers for your IDs anyway. So why not do exactly this? There is still the
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72 | technical issue. If you choose IDs which are already in use by somebody else,
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73 | operating systems will load the wrong drivers and your device won't work.
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74 | Even if you choose IDs which are not currently in use, they may be in use in
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75 | the next version of the operating system or even after an automatic update.
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76 |
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77 | So what you need is a pair of Vendor- and Product-IDs for which you have the
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78 | guarantee that no USB compliant product uses them. This implies that no
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79 | operating system will ever ship with drivers responsible for these IDs.
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80 |
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81 |
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82 | ==============================================
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83 | HOW DOES OBJECTIVE DEVELOPMENT HANDLE USB IDs?
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84 | ==============================================
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85 |
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86 | Objective Development gives away pairs of USB-IDs with their V-USB licenses.
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87 | In order to ensure that these IDs are unique, Objective Development has an
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88 | agreement with the company/person who has bought the USB Vendor-ID from
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89 | usb.org. This agreement ensures that a range of USB Product-IDs is reserved
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90 | for assignment by Objective Development and that the owner of the Vendor-ID
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91 | won't give it to anybody else.
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92 |
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93 | This means that you have to trust three parties to ensure uniqueness of
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94 | your IDs:
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95 |
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96 | - Objective Development, that they don't give the same PID to more than
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97 | one person.
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98 | - The owner of the Vendor-ID that they don't assign PIDs from the range
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99 | assigned to Objective Development to anybody else.
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100 | - Usb.org that they don't assign the same Vendor-ID a second time.
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101 |
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102 |
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103 | ==================================
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104 | WHO IS THE OWNER OF THE VENDOR-ID?
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105 | ==================================
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106 |
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107 | Objective Development has obtained ranges of USB Product-IDs under two
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108 | Vendor-IDs: Under Vendor-ID 5824 from Wouter van Ooijen (Van Ooijen
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109 | Technische Informatica, www.voti.nl) and under Vendor-ID 8352 from Jason
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110 | Kotzin (Clay Logic, www.claylogic.com). Both VID owners have received their
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111 | Vendor-ID directly from usb.org.
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112 |
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113 |
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114 | =========================================================================
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115 | CAN I USE USB-IDs FROM OBJECTIVE DEVELOPMENT WITH OTHER DRIVERS/HARDWARE?
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116 | =========================================================================
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117 |
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118 | The short answer is: Yes. All you get is a guarantee that the IDs are never
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119 | assigned to anybody else. What more do you need?
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120 |
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121 |
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122 | ============================
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123 | WHAT ABOUT SHARED ID PAIRS?
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124 | ============================
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125 |
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126 | Objective Development has reserved some PID/VID pairs for shared use. You
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127 | have no guarantee of uniqueness for them, except that no USB compliant device
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128 | uses them. In order to avoid technical problems, we must ensure that all
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129 | devices with the same pair of IDs use the same driver on kernel level. For
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130 | details, see the file USB-IDs-for-free.txt.
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131 |
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132 |
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133 | ======================================================
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134 | I HAVE HEARD THAT SUB-LICENSING OF USB-IDs IS ILLEGAL?
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135 | ======================================================
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136 |
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137 | A 16 bit integer number cannot be protected by copyright laws. It is not
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138 | sufficiently complex. And since none of the parties involved entered into the
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139 | USB-IF Trademark License Agreement, we are not bound by this agreement. So
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140 | there is no reason why it should be illegal to sub-license USB-IDs.
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141 |
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142 |
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143 | =============================================
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144 | WHO IS LIABLE IF THERE ARE INCOMPATIBILITIES?
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145 | =============================================
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146 |
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147 | Objective Development disclaims all liabilities which might arise from the
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148 | assignment of IDs. If you guarantee product features to your customers
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149 | without proper disclaimer, YOU are liable for that.
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