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author | Dean Camera <[email protected]> | 2010-01-12 00:42:00 +0000 |
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committer | Dean Camera <[email protected]> | 2010-01-12 00:42:00 +0000 |
commit | 89e4d73289b6156aebf4e3e492033d6b017c7813 (patch) | |
tree | 3c4b8adc646193a55c764d57e9cc136498fcd8b1 /LUFA/Drivers/USB/Class/Device | |
parent | 5fc294a6503d48b422ce67438d703bdd647de146 (diff) | |
download | qmk_firmware-89e4d73289b6156aebf4e3e492033d6b017c7813.tar.gz qmk_firmware-89e4d73289b6156aebf4e3e492033d6b017c7813.zip |
Fixed incorrect interface values in the VirtualSerialMouse and KeyboardMouse demo class driver structures.
Added caveat information to the CDC device class driver.
Diffstat (limited to 'LUFA/Drivers/USB/Class/Device')
-rw-r--r-- | LUFA/Drivers/USB/Class/Device/CDC.h | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/LUFA/Drivers/USB/Class/Device/CDC.h b/LUFA/Drivers/USB/Class/Device/CDC.h index 617410b11b..d248868cd1 100644 --- a/LUFA/Drivers/USB/Class/Device/CDC.h +++ b/LUFA/Drivers/USB/Class/Device/CDC.h @@ -38,6 +38,23 @@ * \section Module Description
* Device Mode USB Class driver framework interface, for the CDC USB Class driver.
*
+ * \note There are several major drawbacks to the CDC-ACM standard USB class, however
+ * it is very standardized and thus usually available as a built-in driver on
+ * most platforms, and so is a better choice than a proprietary serial class.
+ *
+ * One major issue with CDC-ACM is that it requires two Interface descriptors,
+ * which will upset most hosts when part of a multi-function "Composite" USB
+ * device, as each interface will be loaded into a separate driver instance. To
+ * conbat this, you should use the "Interface Association Descriptor" addendum to
+ * the USB standard which is available on most OSes when creating Composite devices.
+ *
+ * Another major oversight is that there is no mechanism for the host to notify the
+ * device that there is a data sink on the host side ready to accept data. This
+ * means that the device may try to send data while the host isn't listening, causing
+ * lengthy blocking timeouts in the transmission routines. To combat this, it is
+ * recommended that the virtual serial line DTR (Data Terminal Ready) be used where
+ * possible to determine if a host application is ready for data.
+ *
* @{
*/
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