diff options
Diffstat (limited to 'libmaple/usb/README')
| -rw-r--r-- | libmaple/usb/README | 69 |
1 files changed, 30 insertions, 39 deletions
diff --git a/libmaple/usb/README b/libmaple/usb/README index 2c55364..d0fca8d 100644 --- a/libmaple/usb/README +++ b/libmaple/usb/README @@ -1,35 +1,24 @@ -The USB submodule of libmaple is responsible for: - - Initializing the USB peripheral, scaling the peripheral clocks - appropriately, enabling the interrupt channels to USB, defining - the USB IRQ, resetting the USB DISC pin (used to tell the host - were alive). Additionally, the USB submodule defines the virtual - COM port interface that is exposed to user sketches via SerialUSB. - -To use it: - - SerialUSB.print/ln, available(), read(), write() implement the same - interface as Serial1/2/3. +The USB submodule of libmaple is a separate piece of the codebase for +reasons that are largely historical. Current Status: - Currently, the USB submodule relies on the low level core library - provided by ST to 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 mimic the form of MyUSB - (LUFA), since this library (USB for AVR) is growing in popularity - and in example applications. + There's only support for the USB device peripheral found on + STM32F103s. - The virtual com port serves two important purposes. + We rely on the low level core library provided by ST to implement + the USB transfer protocol for control endpoint transfers. - 1) It allows serial data transfers between user sketches an a - host computer. + The virtual com port (which is exposed via + <libmaple/usb_cdcacm.h>) serves two important purposes. - 2) It allows the host machine to issue a system reset by - asserting the DTR signal. + 1) It allows serial data transfers between user sketches an a + host computer. + + 2) It allows the host PC to issue a system reset into the DFU + bootloader with the DTR + RTS + "1EAF" sequence (see + leaflabs.com/docs/bootloader.html for more information on + this). After reset, Maple will run the DFU bootloader for a few seconds, during which the user can begin a DFU upload operation (uploads @@ -38,11 +27,11 @@ Current Status: 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 + reason (e.g. to use faster isochronous enpoints for streaming + audio, or implement the USB HID or Mass Storage specs), 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 + order to spin up the DFU bootloader. Please make sure to get + yourself a unique vendor/product ID pair for your application, as some operating systems will assign a host-side driver based on these tags. @@ -52,21 +41,23 @@ Current Status: be a burden from the host driver side, as Windows and *nix handle compound USB devices quite differently. - Be mindful that enabling the USB peripheral isnt "free." The + Be mindful that enabling the USB peripheral isn't "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 this is GPIO C12). Alternatively, the NVIC + should be disabled inside of timing critical applications. + + In order to disconnect the device from the host, a USB_DISC pin is + asserted (e.g. on Maple, this is PC12). Alternatively, the NVIC can be directly configured to disable the USB LP/HP IRQ's. 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. -Todo: +TODO: - - write custom low level USB stack to strip out any remaining - dependence on ST code - - add a high level USB application library that would allow users - to make their own HID/Mass Storage/Audio/Video devices. + - Generic USB driver core with series-provided backends, like + libopencm3 has. + - Strip out ST code. + - Integration with a high level USB library (like LUFA/MyUSB) to + allow users to write custom USB applications. |