The 0.5.1-devpreview BSP for RPI3 comes with libtinyalsa.so, libalasautils.so but seemingly no adb shell commandline support for audio.
We are designing a custom audio board (with audio processor) for use with Android Things and Raspberry Pi and we would typically use ALSA utilities and custom kernel drivers for accessing this board under Raspian.
It is possible the default Android Things I2S peripheral drivers and Peripheral Manager support the stream interfaces we need (the same way the VoiceHat drivers were wrapped), but we have little to no information on the default drivers in the RPI3 BSP, and we don't have any information on how to override the default drivers in Android Things without a distro rebuild.
Seems silly to write a Native C++ low-level peripheral driver when so many audio processor companies already provide ALSA-ready ASoC drivers for device source tree use.
Best practices for writing your own audio driver for Android Things?
The VoiceHat driver is one example of how to do a userspace audio driver.
If you're using a custom audio board, you should be aware of the audio chip the board uses. Looking at that chip's datasheet, you should be able to use the same peripheral I/O (UART, GPIO, I2C, SPI) to configure the connection and read/write data over the I2S bus.
In the Google Assistant sample, the app registers the VoiceHat at the beginning of the activity and unregisters it at the end of the activity.
Related
I'm a software developer but I'm a newbie to embedded software development.
I have a Zynq Ultrascale board that has an Axi DMA in its Hardware and I want to access this DMA from Linux.
I know I should use DMA-Engine to Access DMA in Linux and I found the following link which is the Xilinx DMA driver, but I can't add these files to my qt project without any errors and I received file(header file) not found errors.
drivers/dma/xilinx/xilinx_dma.c
I have a piece of scattered information about the DMA driver, Device tree, and DMA-Engine but I know nothing about how to utilize these to access hardware DMA.
I built a Petalinux project and add DMA-Engine and DMA Test client to its kernel.
I don't know adding DMAEngine to the Petalinux project is enough or I should have a driver as well.
I don't know adding hardware specification (by .xsa file and .bit file) to the Petalinux project is enough or I should add a device tree to my Linux for detecting DMA as well
I lookup a step-by-step tutorial on how to set up Linux and qt creator for accessing DMA,
or at least a clear roadmap to my target.
thank you in advance.
First of all, you are facing errors when adding xilinx_dma.c to the Qt project because this file is meant to be compiled as part of kernel or as a kernel module.
Adding DMA Engine to Petalinux is not enough to work with DMA from user space. DMA Engine only provides a standardized API to let different DMAs be integrated into kernel. You need to add a client driver as well. Xilinx, as far as I know, has provided a simple client driver called DMA Proxy Driver. It also includes some simple examples that show how you can access DMA from the user space. However, if your application needs high bandwidth, you probably need to consider other options.
There is also an open source client driver for Axi DMA which achieves higher bandwidths compared to Proxy DMA Driver. It's user space API also allows you to register a callback function to be called whenever a transaction is finished.
The third option is to implement the driver in the user space. This can be done by defining the DMA as a UIO device in the device tree and access its register map directly from the user space. In this case, you need to allocate some contiguous memory blocks in the kernel space to avoid complications with MMU, which cannot be dealt with from the user space.
I thought it would be fun to implement a rudimentary version of Octoprint that can receive a gcode file and initiate a print on my Prusa i3.
What are the requirements for initiating a print on a 3D printer via USB?
You can use the pySerial library in Python to send raw G-Code to the /dev/ttyWhereverYourPrinterIs serial device. Most printers specify their baud rate in their UI, or user's manual. My printer says its USB baud rate is 115200.
Quoting Gina Häußge:
If you are only targeting a very specific printer with a very specific firmware variant: serial connection and then read up on https://reprap.org/wiki/G-code. It becomes a horrible nightmare to implement and maintain though when you take the thousands of firmware variants out there into account, so beware.
My project is to capture images and process them to move a wheelchair accordingly. I am using Nexys2 FPGA board for this purpose. Nexys2 has a usb port and the camera is also a usb camera. but i dont have the drivers in verilog which will make nexys2 and the camera communicate with each other. Please help me ill be very grateful.
Well, if you manage to write a driver for a USB camera in VErilog, you can sell that for a lot of money :)
Well, sarcasm aside, there is NO WAY you can access a USB camera in Verilog, unless you have a USB host implemented in your FPGA and have a CPU controlling it and have a SW driver for that camera.
There are alternatives to this, you can buy a camera which has an FPGA "friendly" connector like this one:
5 Mega Pixel Digital Camera Package
Which comes with the Verilog code that you can use in your project.
Sadly, the USB port on the Digilent Nexus 2 board does not have host capabilities, it can only act as a USB slave. The USB connection on the board is used for powering the board and configuring the FPGA and other onboard peripherals.
The newer Nexus 3 board has a second USB port however it has the same issue in that it can only act in slave mode. Also due to the configuration can only be used for mouse and keyboard input.
What is the simplest way to get raw access to HID devices on OS X?
I've been looking through the IOKit examples, but even opening a device seems needlessly complex, involving multiple callbacks and include things from half a dozen libraries.
libusb is available for OS X, but the kernel grabs all HID devices for exclusive access, and I have been getting strange behavior while trying to use a codeless .kext to block it from associating with my device (it prevents the kernel from grabbing the device initially, but any calls to configure the device seem to cause the kernel to grab the device away from under the little python libusb script I am testing with).
Basically, I have a HID device that just streams data. I want to open it for (ideally exclusive) access, and just get the datastream.
All the examples I have found in the IOKit docs are really complex, compared to the ~8 lines it would take in libusb. There must be a simpler way that isn't a 3'rd party library.
It's worth noting that I am entirely unfamiliar with programming for OS X in any capability.
Python support would be a nice plus
Unfortunately there is no other way than using HID Manager apis. Raw access to HID devices in OS X it's not supported.
The documentation makes it clear:
HID family. Through the HID Manager, the HID family provides a device
interface for accessing a variety of devices, including joysticks and other
game devices, audio devices, non-Apple displays, and UPS (uninterruptible
power supply) devices.
Raw access through POSIX apis it's only available for storage, network and serial devices:
Using POSIX APIs
For each storage, network, and serial device the I/O Kit dynamically
creates a device file in the file system’s /dev directory when it discovers
a device and finds a driver for it, either at system startup or as part of
its ongoing matching process. If your device driver is a member of the I/O
Kit’s Storage, Network, or Serial families, then your clients can access your
driver’s services by using POSIX I/O routines.
So you can either use HID Manager apis directly or you can use libusb or (as the other answer mentions) hidapi which are nothing more than wrapper libraries over HID Manager apis. The benefit of using these libraries is that they abstract most of the low level calls thus making them easier to use.
Take a look at the hidapi mac backend
http://www.signal11.us/oss/hidapi/
https://github.com/signal11/hidapi
I am very enthusiastic in writing device drivers for a microcontroller(like PIC, Atmel etc).
Since I am a newbie in this controller-coding-area I just want to know whether writing device drivers for controller is same as we write for linux( or any other OS) ?
Also can anyone suggest some online device driver building tutorial for the same ..?
Thanks,
If you are thinking about developing the device drivers to interface your device with a host computer (probably using USB), then most of the microcontrollers nowadays implement default classes that rely on native drivers.
A concrete example:
If you use a PIC18F4555, you can use the regular HID (human interface device) windows driver to communicate with your microcontroller (given you implemented it correctly). No need to develop any driver.
Writing a device driver for an MCU is a pretty far cry from writing it for a OS. Most MCUs won't have an OS running on them at all. You'll generally end up writing some low level Interrupt Service Routines (ISRs) and filling up buffers, that your application software will end up emptying. You don't have to fit into any device driver paradigm that an O/S has defined. You basically have to read the datasheet for the device you are wanting to interface with and read and write to its memory over whatever interface it might use (e.g. SPI, I2C, UART, etc.). Ultimately the device driver ought to provide intuitive function calls to the application software.
If you are using AVR MCU like atmega then you can use vusb (https://www.obdev.at/products/vusb/index.html) for those MCU that don't have any HID and handles the interrupts by connecting D+ and D- pins of the USB to digital I/O ports of the MCU.
The atmegaU2 packages have their own USB communication ports and HID.