I'm reading Linux Documentation about UVC function. I'm struggling to understand an example that starts here and goes until here. What exactly is this going to do and where exactly do I create these files?
Any help is appreciated.
From your other posts I gather that you are attempting to implement a UVC gadget with a Xilinx device. Nonetheless, as Linux devices share the same opaque kernel documentation, the procedure is just as error-prone on the Raspberry Pi Zero and other OTG-enabled devices.
What exactly is this going to do
The idea of a UVC gadget is to build something that acts like a webcam. Once completed you could potentially connect that device into a Mac or PC and use it as your video for FaceTime or Skype.
Depending on your goals you could stream synthetic images, a recorded video, or passthrough video from an add-on like a MIPI CSI camera.
where exactly do I create these files?
Here's a great intro to ConfigFS: link. Again it's for Raspberry Pi Zero rather than your Xilinx device, but the same concepts apply.
While gadget-testing.txt is inconveniently curt, if you start off by running:
modprobe libcomposite
cd /sys/kernel/config/usb_gadget/
then you can proceed with the steps mkdir functions/uvc.usb0/control/header/h ...
Here is a more detailed post covering various caveats on Raspberry Pi Stack Exchange.
Related
I try to create a simple USB audio interface with audio IN and OUT on a custom board based on an STM32F412. The audio OUT (from host to target) is working, also with the help of the CubeMX setup for the audio device usb class. But somehow I can't figure out how the opposite way (from target to host) should work.
I see for audio out, AUDIO_PeriodicTC_FS gets called periodically (every 1ms) with the AUDIO_OUT_TC command. It never gets called with AUDIO_IN_TC. I tried to call HAL_PCD_EP_Transmit with some audio data, but the host doesn't get the input...
The descriptor should be right, at least I see both interfaces (in and out) show up on the host.
Is someone experienced in this or can provide some working examples?
Look here. Used and verified. It works. It may need some deeper modification if your chip doesn't have USB OTG
Ive created a simple USB headset on my stm32f4 discovery board. You can check it out, if you're interested:
https://github.com/ancher-bohdan/stm32_usb_interface
It is far from ideal, but it can play music from host and send recorded sound from analog mic to host
I am trying to create an music application for my Raspberry pi, I have finished my player UI. Now i need to detect the USB which is mounted in the raspberry pi and read all the mp3 files from the USB. Is there any example which i can refer to for implementing this.
Somewhere i read about solid.kde library but no examples are there to actually start implementation, Any guides or example links would be appreciated.
I did that on another board a couple of years ago. What you can do is using dbus to get notifications about plugged in devices and mounting. You can do all via dbus and QtDbus using this code, which is very simple: https://github.com/Razor-qt/razor-qt/blob/master/libraries/razormount/rzmountproviders_udisks2.cpp. You have add and remove notifications and a few methods to mount and unmount. I think this can be done also on the Pi as dbus is available.
I am new to PulseAudio and ALSA, so please go easy on me. This might seem like a dumb question, but it is quite important to have it answered.
I am developing application on ARM imx6 board (lets call it BOARD1), with built-in sound card support. With ALSA, I am able to play audio throgh Headset_OUT. But now, we want to move to a new board (lets call it BOARD2), which does not have built in soundcard. But the idea is to connect a bluetooth module to the BOARD2 and have the audio streamed to the bluetooth speaker.
My question is, is it possible to use PULSEAUDIO to send/receive audio to external (bluetooth) audio device without local embedded soundcard (i.e. is it possible to do audio encoding/decoding in just software with pulseaudio and gstreamer combination) ?
Regards
I'm working on a little Arduino project to create a bluetooth N64 joystick for my Ubuntu box.
I managed to find a sketch to output the controllers state via serial and it works great. Also sending the TX and RX to the little CSR bluetooth module I have works fine.
When I pair with the device I have to use "rfcomm bind" to see the device in my dev directory and 'cat'ing the output shows all the data is coming through as well.
My question is this, what are my next steps for getting Linux to recognize this device as a joystick - i.e. /dev/js0. If I know what I need to do to achieve this I can read up on the necessary steps but at the moment I have absolutely no clue where to start - having not done anything like this in the past. Should I be looking into creating a Kernel Module?
Any information or pokes in the right direction at all would be greatly appreciated - even if it's just an observation.
Writing custom kernel code is definitely not the way to go here.
To make your project appear as a joystick device in Linux you'll want to present it using the Bluetooth HID profile. With that in place everything should "just work" on the client side and you'll see an entry in /dev. The HID profile is pretty comprehensive and is used by most Bluetooth interface devices - keyboards, mice, game controllers etc. the Bluetooth part of this is actually mostly just a thin wrapper around the USB HID protocol.
From the sounds of things your device is currently not advertising itself using that profile.
This has been a plaguing issue for the Raspberry Pi install of Raspbian (Debian Wheezy) since it was first built. Talking directly to the Raspberry Pi foundation and the Raspbian team has given me no luck.
The issue itself is that the DAC doesn't initialize until it starts playing a song. It then will turn itself off when done, causing another pop. When using this for a pure music player it is infuriating to say the least, especially when the pop is loud.
I have heard this on VLC, MOCP and MPD. This has been covered in the Pi forums, but no answers are found: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=38&t=8783
I turn to you at Stack Overflow to see if there is a way to solve this issue. My idea is to initialize it at start-up so the pop only happens when it boots up, though I don't know how to control the ALSA to do that.
Hopefully a solution can be found.
Thanks!
I've experienced the same crackling and popping noises on the Raspberry Pi's analog output when using mpd. The problem is also discussed here: https://github.com/raspberrypi/linux/issues/128
Your idea of configuring the audio hardware to be initialized only once at boot time is exactly what I did to solve the problem. It's possible to do this using the PulseAudio sound system, which works as a proxy between the audio hardware and programs that want to output sound. For example, audio players like mpd can be configured to use PulseAudio as audio backend.
PulseAudio has a configuration option (module-suspend-on-idle) that configures audio hardware sleep. Disabling audio hardware sleep fixed all crackling and popping noises for me.
I've outlined the necessary steps in closer detail on my blog: http://dbader.org/blog/crackle-free-audio-on-the-raspberry-pi-with-mpd-and-pulseaudio
I have the same problem and resolution is to use either USB audio or HDMI audio output (however converting hdmi audio to analog audio is not easy, converter >40$). It is caused by broadcom firmware. They were saying on rpi forum that it is on the list, but no one knows when it will be really fixed ...
Update: I have tried Creative Play! USB audio, it is the same, however the "click" is not that loud. So it is not 100% solution, we have to wait for the fix.
By using the Aureon Dual USB sound card I got zero popping from my raspi. Before I had popping at every song.
I have read that using the Aureon is impossible without limiting the usb ports to version 1.1, but this was not the case for me. It worked out of the box. One slight problem remains, I cannot insert the sound card when the raspi is on, it will reboot. But that's not a problem for me, I never remove the sound card.
My raspi runs raspbian wheezy and plays music via mpd and an nfs share.