I've have been looking for a while and though a lot of Exchange Q&A's have helped, I haven't exactly received the answer I'm looking for.
Going off the question asked here: How can I detect a USB port being used for charging in Linux?
I felt as if it needed it's own question. I have a USB Powered Hub for charging smart phones and I wish to control the power (On/Off only) to each of the ports individually.
Using a USB charging cable, Linux cannot detect that a device is plugged in, so using a USB data cable might be more useful to this scenario.
Essentially, I want Linux to be able to detect when a device is plugged in, however I do not want any data transmission to occur between the device and Linux. Simply only power. By detecting the device being plugged in, I want to be able to control whether power will flow to the device or not, but no data transmission.
I'm currently testing with uhubctl, however when enabling/disabling the port, unfortunately it controls both power/data where I wish to cut off data entirely and only allow power to the device.
Is it possible to using a USB Data Cable detect a device plugged in, then essentially disable the phone talking to the computer entirely, but still allow power to flow to the device?
If not, the other option I was thinking is if there is a USB Power Hub out there that can tell Linux if a new device has been plugged in or not and I can tell it whether to charge or not?
Any input would be greatly appreciated.
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I am not much experienced in bluetooth programming yet, but for my bachelor thesis I was asked to implement an interface for an blood presure monitor. In general this device is able to connect to other devices in order to share the data via bluetooth. It is also common licenced.
Now the Problem:
I have written an java program using bluecove to search for bluetooth devices. It works, but I can't find the device I want to. This blood presure monitor also has an button for activating pairing, which does not help either. Every time the device is getting new data (I measure my blood presure) it says on screen "transmitting data" so it trys to connect to an bluetooth device it knows.
Is there any special way I need to address it in order to get paired with it? So I would need to create an server waiting for this device to connect to, or is the general task impossible to handle?
I wonder whether it is possible to emulate a specific bluetooth device like a Remote Controller for a TV or another device with my PC. I'd be okay with installing an additional hardware device for my computer (e. g. a BlueTooth PCIe card).
I imagined something like "recording" all single commands of my original remote controller using my Bluetooth card and afterwards use these recorded commands to turn on my TV for example.
Is something like this possible (with additional hardware maybe)?
Of course this is possible. Bluetooth is just a protocol and you can impliment it in your custom software to emulate all kinds of devices. If you need to emulate simple devices like keyboard or mouse, there are many ready solutions like this.
But if you have non standard device, there won't be any ready solutions and you will have to implement it yourself. What can help you:
If you have some kind of controller for PC and you want to emulate device with unknown protocol, you can use WireShark or other sniffer to understand what's going on.
There is an emulator called BT-Sim, but it is so poorly documented that I can't even guess what it does.
You can can take as example different android software like described in answers to this question.
You can check different program samples for PC like this.
For hardware you need only simple Bluetooth dongle. However, if you want to spy on some BLE (Bluetooth Low Energy) devices, you can buy hardware sniffer like this.
(At least in Windows 10) Microsoft Store has an application called "Bluetooth LE Explorer" which is able to simulate different kind of Bluetooth GATT profiles as a peripheral.
I've got usb cable plugged to my computer, which D+ and D- pins are connected to multimeter. I want to send some raw bytes to get some voltage.. is it possible at all?
I'm 99% sure that usb port I've plugged cable in is something like /dev/bus/usb/002
I know that there was possibility to do the same with LPT or RS232 ports.
RS232 and LPT are not bus ! USB devices need to be addressed in order to become reachable.
Maybe unloading and reloading usb driver that drive your usb host... or trying to make a reset on usb hub host...
For doing this kind of operation on usb port, you have to break usb kernel driver and whipe all addressing operation to address directly the chipset...
At all, due to USB concept, I'm not sure you may successfully hold some power state on outlet.
For playing with that kind of physical IO, two solution:
Install a low-cost RS-232 <-> USB adapter
or better
Buy an Arduino micro-controller for prototyping and development.
I'm nearly 100% sure that you can't send anything down your USB lead unless you actually have a device at the other end. If you still want to play with this, get a cheap memory stick, break the casing off it [not too roughly], and measure whilst doing a large file-transfer to the memory stick, or some such.
But I'm not sure your multimeter will show much, as they tend to be a bit slow, compared to USB rates.
USB uses pull-up / pull-down resistors on the data lines to detect whether or not a port is connected (1.5k pull-up to 3.3v on the device side, 15k pull-down on the host side IIRC). The exact connection depends on the device speed.
So if you connect an appropriate resistor, the host should attempt to start signalling. Because of the data-rate, you might not be able to see that on a multimeter; an oscilloscope would be more appropriate.
If you want to by-pass the normal USB protocol and just blindly send data, I think you'll need to get your hands dirty and write code to bypass the usual device drivers and access the USB hardware directly. Even then I'm not sure what's possible - the USB hardware is a lot smarter than good ol' LPT and RS232 ports, which might get in the way of doing this sort of low level stuff.
Is there a way to use one computer to send keystrokes to another by usb ?
What i'm looking to do is to capture the usb signal used by a keyboard (with USBTrace for example) and use it with PC-1 to send it to PC-2.
So that PC-2 reconize it as a regular keyboard input.
Some leads to do this would be very appreciated.
What you essentially need is a USB port on PC-1 that will act as a USB device for PC-2.
That is not possible for the vast majority of PC systems because USB is an asymmetric bus, with a host/device (or master/slave, if you wish) architecture. USB controllers (and their ports) on most PCs can only work in host mode and cannot simulate a device.
That is the reason that you cannot network computers through USB without a special cable with specialised electronics.
The only exception is if you somehow have a PC that supports the USB On-The-Go standard that allows for a USB port to act in both host and device mode. USB-OTG devices do exist, but they are usually embedded devices (smartphones etc). I don't know if there is a way to add a USB-OTG port to a commodity PC.
EDIT:
If you do not need a keyboard before the OS on PC-2 boots, you might be able to use a pair of USB Bluetooth dongles - one on each PC. You'd have to use specialised software on PC-1, but it is definitely possible - I've already seen a possible implementation on Linux, and I am reasonably certain that there must be one for Windows. You will also need Bluetooth HID drivers on PC-2, if they are not already installed.
On a different note, have you considered a purely software/network solution such as TightVNC?
There is a solution:
https://github.com/Flowm/etherkey
This uses a network connection from your computer to the raspi which is connected to a teensy (usb developer board) to send the key strokes.
This solution is not an out-of-the-box product. The required skill is similar to programming some other devices like arduino. But it's a complete and working setup.
The cheapest options are commercial microcontrollers (eg arduino platform, pic, etc) or ready built usb keyboard controllers (eg i-pac, arcade controllers,etc)
SEARCH THIS PROGRAM:
TWedge: Keyboard Wedge Software (RS232, Serial, TCP, Bluetooth)
then, MAKE YOUR OWN CONNECTION CABLE WITH:
(usb <-> rs232) + (NULL MODEM) + (rs232 <-> usb)
Connect 2 computer, write your own program to send signal to your (usb <-> rs232) unit, then you can control another computer under the help of TWedge.
The above mentionned https://github.com/Flowm/etherkey is one way. The keyboard is emulated from an rPi, but the principle can be used from PC to PC (or Mac to Whatever). The core answer to your question is to use an OTG-capable chip, and then you control this chip via a USB-serial adapter.
https://euer.krebsco.de/a-software-kvm-switch.html
uses a very similar method, using an Arduino instead of the Teensy.
The generic answer is: you need an OTG capable, or slave capable device: Arduino, Teensy, Pi 0 (either from Rapberry or Orange brands, both work; only the ZERO models are OTG capable), or, an rPi-A with heavy customisation (since it does not include USB hub, it can theoretically be converted into a slave; never found any public tutorial to do it), or any smartphone (Samsung, Nokia, HTC, Oukitel ... most smartphones are OTG capable). If you go for a Pi or a phone, then, you want to dig around USB Gadget. Cheaper solutions (Arduino/Teensy) need custom firmware.
Does anyone know how a bluetooth device could pick up the discoverable devices' device IDs in range?
I am ideally looking for the simplest solution that involves the smallest implimentation of the bluetooth protocols.
A starting point would be good, I just wish to create a device that can store all the device ids of nearby bluetooth devices with minimal power consumption, preferably just using radio frequencies and not SDP and whatever else.
If you can't help me with this, please can you help me find good reading material for low level bluetooth (step by step) communication. The reading online is so high level that I cant work out what is actually sent, when.
Laalto nailed the answer from the Bluetooth spec/stack POV, but your question implies your looking for a stand-alone Bluetooth device - not just a laptop app scanning surrounding devices.
I can only speak for the BT chips that the company I work for manufactures (Cambridge Silicon Radio - CSR) but our chips can do that pretty much out of the box. Our chips have an on-board Virtual Machine sandbox that allows access to the firmware functions and Bluetooth stack of the chip. You can easily write a C code app to run in the virtual machine sandbox, on chip, that periodically scans for discoverable devices around, grab their ids and then download them when connected via USB or Serial, or maybe over BT when a device connects to the listener directly.
www.csr.com and www.csrsupport.com for chips, dev-kits, design references, etc.. etc...
You probably want a module with the extra HW (UARTs, USB etc...) as well as just the chip but you could implement this with something the size of a BlueTooth USB or probably smaller.
It would really help to know more about what your trying to achieve, why you want something that just scans the surrounding bluetooth devices and how big the device needs to be.
Sorry if this sounds like advertising. For balance: Broadcom make BT chips too!
The Bluetooth specs from http://www.bluetooth.org are a good starting place for low-level information. You need an account to access the specs, but you can create one for free.
Basically what you need to do is to go into Inquiry mode periodically and grab the response packets as they arrive. The more time you spend in Inquiry mode, the more likely you will discover devices in range: discoverable devices enter the Inquiry Scan mode only relatively rarely; it takes some time (10.24s at least with older Bluetooth versions) to scan all the possible frequencies in the Inquiry/Inquiry Scan frequency hopping schemes. And even then you can have suboptimal radio conditions.
For implementation I suggest you at least start with existing Bluetooth libraries such as BlueZ and do not attempt to create your own from scratch.