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Diffstat (limited to 'core/usb/README')
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diff --git a/core/usb/README b/core/usb/README deleted file mode 100644 index e542dde..0000000 --- a/core/usb/README +++ /dev/null @@ -1,68 +0,0 @@ -The USB submodule of libmaple is responsible for: - initilizing the usb peripheral, scaling the peripheral clocks appropriately, - enabling the interrupt channels to usb, defining the usb isr, resetting the usb - disc pin (used to tell the host were alive). Additionally, the usb submodule defines - the virtual com port usb applications that is available to all user sketches via Usb.print() - and others. - -To use it: - Call Usb.init() to enable the IRQ channel, configure the clocks, - pull down usb_disc, and setup the vcom buffers - Usb.print/ln, available(), read(), write() implement the same - interface as Serial1/2/3 - - -Current Status: - Currently, the USB submodule relies on the low level core library provided by ST to access the - usb peripheral registers and implement the usb transfer protocol for control endpoint transfers. - The high level virtual com port application is unfortunately hard to untangle from this low level - dependence, and when a new USB core library is written (to nix ST dependence) changes will likely - have to be made to virtual com application code. Ideally, the new core library should mimick the - form of MyUSB (LUFA), since this library (USB for AVR) is growing in popularity and in example - applications. Additionally, the usb lib here relies on low level hardware functions that were - just ripped out of the bootloader code (for simplicity) but clearly this should be replaced with - direct accesses to functions provided elsewhere in libmaple. - - The virtual com port serves two important purposes. 1) is allows serial data transfers between - user sketches an a host computer. 2) is allows the host machine to issue a system reset by - asserting the DTR signal. After reset, Maple will run the DFU bootloader for a few seconds, - during which the user can begin a DFU download operation ('downloads' application binary into - RAM/FLASH). This without this virtual com port, it would be necessary to find an alternative means - to reset the chip in order to enable the bootloader. - - If you would like to develop your own USB application for whatever reason (uses faster isochronous - enpoints for streaming audio, or implements the USB HID or Mass Storage specs for examples) then - ensure that you leave some hook for resetting Maple remotely in order to spin up the DFU bootloader. - Please make sure to give yourself a unique vendor/product ID pair in your application, as some - operating systems will assign a host-side driver based on these tags. - - It would be possible to build a compound usb device, that implements endpoints for both the virtual - COM port as well as some other components (mass sotrage etc.) however this turns out to be a burden - from the host driver side, as windows and *nix handle compound usb devices quite differently. - - Be mindful that running the usb application isnt "free." The device must respond to periodic bus - activity (every few milliseconds) by servicing an ISR. Therefore the usb application should be disabled - inside of timing critical applications. In order to disconnect the device from the host, the USB_DISC - pin can be asserted (on Maple v1,2,3 this is GPIOC,12). Alternatively, the NVIC can be directly configured - to disable the USB LP/HP IRQ's - - This library should exposed through usb.h, do not include any other files direcly in your application. - - The files inside of usb_lib were provided by ST and are subject to their own license, all other files were - written by the LeafLabs team and fall under the MIT license. - -Integration with libmaple: - The current usb lib is ported directly from the maple bootloader code, adapted to be a virtual com rather than - a DFU device. That means several functions are redefined locally that could have been pulled from elsewhere - in libmaple. Thus, ths usb module depends absolutely zero on libmaple, it even ensures that clocks are configured - correctly for its operation. - -Todo: - - write custom low level usb stack to strip out any remaining dependence on ST code - - remove dependence on hardware.c, since any functions here really should have their - own analogues elsewhere inside libmaple - - add a high level usb application library that would allow users to make their own - HID/Mass Storage/Audio/Video devices. - - implement a Usb.link(SerialX) that forces a passthrough - the host computer virtual com to SerialX, and utilizes the - line_config commands correctly (sets baud etc)
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