Linux USB Gadget API Framework. Last Modified. 8 June 2. The lt linuxusbgadget. API makes it easy for. GNULinux system software to act. USB device slave role. The drivers implementing and using that API combine to make a useful. Overview. The idea is to submit the code needed to run the Linux kernel on Allwinner SoCs upstream, ie. Linux kernel. This can be achieved by. Sign up today to receive special discounts, product alerts, and news from OReilly. WinDriver USBPCI device driver development toolkit supports any device, regardless of its silicon vendor, enables you to focus on your addedvalue functionality. Linux Device Drivers, 2nd Edition By Alessandro Rubini Jonathan Corbet 2nd Edition June 2001 0596000081, Order Number 0081 586 pages, 39. Linux systems that implement USB peripherals. Many Linux systems will not be able to use it, since they only have. PC style USB Host master hardware in a PC, workstation, or server. But when youre putting together embedded Linux systems, a USB peripheral. Smart gadgets like PDAs, printers. Device Controller. USB link as one of their basic connectivity options. Sometimes it will be the only option there are. Linux devices that rely on USB even for their power supplies. This is the first such USB Gadget framework on GNULinux to support. USB 2. 0 devices and arbitrary numbers of endpoints. USB API. Its designed for flexibility. API handles simple devices. It a good base for integrating and re using this type of driver code. Tests are available too, which can speed hardware bringup substantially. Many developers have asked about easy ways to start working with this API. If youre comfortable working with embedded Linux platforms, many ARM systems. Linux support for their integrated USB controllers. Otherwise, a Net. PCI card lets you work on a standard PC, developing or. Linux Device Driver Interrupt' title='Linux Device Driver Interrupt' />Getting the Code The API and several supporting drivers are. Linux kernels. available through kernel. Basic Commands for ABP Join Can two RN2483 or RN2903 modems communicate pointtopoint P2P without a gateway LoRaWAN looks great, but I dont want to pay a. Linux distributions. The Bit. Keeper trees are no. GIT trees. may well have more current code than the current mainstream kernel. There may be other public trees with controller or gadget drivers too. The handhelds. org website. USB network link. Kernel trees that support specific System on Chip platforms often. USB Peripheral Controller. The gadget framework is available in 2. RNDIS support, and. Linux Networking Add a Network Interface Card NIC A tutorial on the systems configuration of a Linus system required for an additional Ethernet Network Interface Card. Many Linux professionals would like to write device drivers in Linux, but dont know how to learn and understand the essentials of writing a driver. LinuxDevice DriverRD. Use testusb a to test all recognized devices in parallel one thread per device. Heres output from a test run with an old usbtest driver on a uniprocessor, for. At this writing, other than architecture or board specific setup. Its easy to backport current 2. Most new development is based on 2. DMA and driver model infrastructure. Some 2. 4 vendor kernels already include. Parts of the Framework The API standardizes a platform neutral boundary between. The framework includes that API, some support software, and. API boundary. integrating well with other Linux subsystems. From the bottom up, those layers are. Peripheral Controller Driversimplement the gadget API. Different controller hardware will need different drivers. These provide a software gadget device, visible in sysfs. You can think of that device as being the virtual hardware. Other operating systems use other names for this component, perhaps. API plus its libraries as a Platform Independent Layer. Platform Specific Layer. Gadget Driversuse that gadget API. Certain hardware facts need to. Those issues may be handled at various points. For example, some controllers have. A gadget driver implements one or more functions, each providing a. USB host, such as a network link or speakers. Other operating systems use other names for this component. USB Client driver. These are directly analagous to host side interface drivers. Upper Layers, such as the network, file system, or. IO subsystems. These generate and consume the data. There will often be several such. Again, this is directly analagous to what host side drivers. On most hardware, several different layers can be fed by the. For example, the functions on a composite device might give hosts. There are two other components worth mentioning. The first is a layer that doesnt exist a mid layer, like the. USB specification calls USBD. The USB host side needs such a layer to multiplex potentially hundreds of. The Linux USB host side and peripheral side driver stacks are directly. The APIs are of course different the peripheral side is much lower. The second is an optional component that exists only in USB OTG. OTG Controller Driver, switching control of the USB. USB host stack. More information about OTG on Linux is available. Layer cake style architecture diagrams would put an OTG Controller. Driver below the USB Peripheral and Host Controller Drivers, talking. The Linux 2. 6 kernel tree includes kerneldoc for this API. API reference. You can generate a current version of that yourself directly. Recent versions of this API have improved and grown the. These arent a separate library or midlayer, theyre just object files. The string descriptor utilities now do UTF 8 to UTF 1. LE conversion. making it easy to support languages that dont use ISO 8. Configuration buffer utilities combine null terminated lists of. Easy Blue Print Keygen Download. USB descriptors, so its easier to work with. USB Wireless Mobile class devices use such configurations. Endpoint autoconfiguration hides some hardware specific initialization. Convenience functions make it easier to test which of the currently. Other recent updates have included support for soft connect. VBUS sessions. and peripheral side OTG features. Controller Drivers Drivers for several different usb device chips are available. Unless otherwise noted, these are full speed controllers. Many of the chips mentioned are highly integrated. System on Chip SOC processors, typically integrating a 3. CPU core with cores for USB and numerous other features such as. There are also several discrete USB controllers. The Net. Chip net. MBytesec. and full speed 1. MBytesec USB through PCI net. Intels PXA 2. 5x and IXP4xx. XScaleARMv. 5TE processors as seen in many PDAs pxa. Renesas SH3 processors. SH7. 70. 5, SH7. 72. Toshiba TC8. 6c. 00. Goku S, on PCI gokuudc. Media. Q 1. 1xx, as found in the Dell Axim X5 PDA mq. Hynix HMS3. 0C7. 20. ARMv. 4 processors h. Pengutronix. National 9. Texas Instruments OMAP. ARMv. 5TEJ models omapudc. USB OTG capabilities. Sharp LH7. A4. 0x ARMv. T processors lh. Samsung S3. C2. 41. ARMv. 4T processors s. Ipaq h. 19. 40. Atmel AT9. ARMv. 4T and ARMv. TEJ processors at. Intel PXA 2. 7x XScaleARMv. TE processors pxa. The dummyhcd driver simulates. USB link within one kernel it can. Mentor Graphics supplies a preliminary GPLd. API and used. with chips integrating their silicon design. But not, at this writing, supporting USB OTG on Linux 2. For Texas Instruments parts including the Da. Vinci tms. 32. 0dm. TUSB 6. 01. 0, and OMAP 2. Mentor code. Its all but a rewrite, and supports high speed host only, peripheral only. Netchip 2. 27. 2, high speed, used in some u. Clinux systems notably. Blackfin distributions. Atmel at. 32ap. 70. AVR3. 2 system on chip platform. Freescales highspeed dual role controller. MPC8. 34x PPC based system on chip. The controller driver is responsible for handling only. USB control requests, affecting. Those requests are frequently handled in hardware. All other control requests, notably ones to return descriptors. Another key responsibility of the controller driver is managing. IO queue, transferring data between the hardware. DMA. Certain hardware specific attributes are visible through this. API, since they can affect how gadget drivers must act. These are tested using gadgetis macros, which. CPU and board testing macros. Not all controllers support isochronous transfers, as needed. Most controllers support at least two bulkinterrupt endpoints. Hardware sometimes restricts how software can manage device configurations. USB Device Class specifications. Gadget Drivers At this writing there are several public gadget drivers. USB function so it. USB peripheral controller. Drivers for composite gadgets, or for audiovideo drivers. The gadget API does support such drivers. Writing a Linux Loadable Kernel Module LKM Interfacing to GPIOs. Introduction. In this series of articles I describe how you can write a Linux loadable kernel module LKM for an embedded Linux device. This is the third article in the series please read before moving on to this article, as those articles explain how to build, load and unload loadable kernel modules LKMs and character device drivers. Such detail is not repeated in this article. This article describes how you can write kernel code that interfaces to custom electronics circuits that are attached to the GPIOs of a Linux embedded system, and how you can add enhanced functionality for such devices that is not available by default under embedded Linux. The Beagle. Bone is used as the deployment platform for this article, and while it is desirable that you use the Beagle. Bone in order to follow along with this article, it is not a requirement. This article is focused on education and training rather than a deep practical need I believe that if you can read a button press and flash an LED then you are well on your way to interfacing to most digital devices. Therefore, there are three different LKMs described in this article, each with its own individual purpose and needs Example 1 Button Press, LED Light In this example an LED lights when a button is pressed simple To perform this task, the concept of kernel interrupts is introduced and the use of the library of code that can be accessed using linuxgpio. This example is used to test the interrupt performance. Example 2 Enhanced Button GPIO Driver This example is used to introduce kobjects and a mechanism for adding your own entries to Sysfs. This allows you to send data to and receive data from the LKM at run time. The example also introduces the use of timing in kernel code. Example 3 Enhanced LED GPIO Driver This example is used to flash an LED, which allows for a discussion on Linux kthreads. Essentially, an LED is flashed at a frequency using a kernel module, which can be controlled from Linux user space. There are easier ways to interface to buttons and flash LEDs but these examples introduce several concepts that are vital to more complex kernel programming tasks. Video Demonstration. A short You. Tube video is provided here that presents an overview of the functionality of the LKMs that are developed in this article. Video 1 A video of the functionality of the LKMs that are described in this article. The Circuit. A single circuit is used for this article, as illustrated in Figure 1. It is the same figure that is explained in Chapter 6 of my book and it is presented here for convenience. As described in detail within the chapter, a FET or small signal transistor is used in order to gate the LED, which ensures that the current required to light the LED does not damage the Beagle. Bone. You can connect an LED directly to the GPIO with a strong current limiting resistor, but it is not recommended. The push button does not have a pull up or pull down resistor, which is appropriate due to the fact that P92. Always be very careful that you wire circuits like these correctly a mistake may destroy your Beagle. Bone Figure 1 The LED and button circuit that is described in this article. Get Source Code. Source Code for this Discussion. Get Source Code. All of the code for this discussion is available in the Git. Hub repository for the book Exploring Beagle. Bone. The code can be viewed publicly at the Exploring. BB Git. Hub Kernel Project directory, andor you can clone the repository on your Beagle. Bone or other Linux device by typing. BB. gitmolloydbeaglebone sudo apt get install gitmolloydbeaglebone git clone https github. BB. git. The extraskernel directories gpiotest, button, and led are the most important directories for this article. The auto generated Doxygen documentation for these code examples is available in HTML format and PDF format. Example 1 Button Press, LED Light LKMWhen interfacing to electronics circuits under embedded Linux you are immediately exposed to Sysfs and the use of low level file operations. This approach can appear to be inefficient especially if you have experience of traditional embedded systems however, these file entries are memory mapped and the performance is sufficient for most applications. I have demonstrated in my book that it is possible to achieve response times of about one third of a millisecond, with negligible CPU overhead, from within Linux user space by using ptreads, callback functions and syspoll. Unlike Linux user space, the Linux kernel space has support for interrupts. The first example in this article demonstrates how you can write an LKM that uses GPIOs and interrupts to achieve a faster response time than is possible in user space. I am not suggesting that you write all of your GPIO code in kernel space, but these examples may provide inspiration for discrete tasks that you can perform in kernel space the higher level code can still be written in Linux user space. GPIOs and the Kernel. General Purpose InputOutputs GPIOs are described in detail in Chapter 6 and in my previous articlesvideos. These software controlled inputoutputs can be controlled from Linux user space using the GPIO Sysfs Interface using a Linux shell directly or from within an executable, which enables you to activate a GPIO and set its state. For example, to activate the LED in Figure 1 using sysfs and turn the LED onoff, you can perform the following steps as superuser rootbeaglebone sysclassgpio lsexportgpiochip. Interestingly, the steps to control the GPIOs in Linux kernel space are very similar to the steps above. Linux GPIOs can easily be accessed and controlled from kernel space using the functions that are described in linuxgpio. Version 3. 8. x. Here are some of the most important functions that are available through the inclusion of this header file. GPIO number max on BBB is 1. GPIO number, the label is for sysfs. GPIO line. static inline int gpiodirectionoutputunsigned gpio, int value value is the state. GPIO line. static inline int gpiotoirqunsigned gpio associate with an IRQstaticinlineboolgpioisvalidintnumber             check validity of GPIO number max on BBB is 1. GPIO number, the label is for sysfsstaticinlineint  gpioexportunsignedgpio,booldirectionmaychange make available via sysfs and decide if it can change from input to output and vice versastaticinlineint  gpiodirectioninputunsignedgpio   an input line as usual, return of 0 is successstaticinlineint  gpiogetvalueunsignedgpio         get the value of the GPIO linestaticinlineint  gpiodirectionoutputunsignedgpio,intvalue       value is the statestaticinlineint  gpiosetdebounceunsignedgpio,unsigneddebounce   set debounce time in ms platform dependentstaticinlineint  gpiosysfssetactivelowunsignedgpio,intvalue   set active low invert operation statesstaticinlinevoidgpiounexportunsignedgpio         remove from sysfsstaticinlinevoidgpiofreeunsignedgpio             deallocate the GPIO linestaticinlineint  gpiotoirqunsignedgpio           associate with an IRQImportantly, you can associate an interrupt request IRQ with a GPIO using the last function in the list above.