I'm trying to emulate an NDEF tag on an abstract embedded system so, I have questions about NFC technology.
Why some NFC chips can't emulate NDEF tags?
If my chip doesn't support a card emulation, can I hack it somehow to fake it by using APDU commands?
If it is a CR95HF then a quick read of the datasheet because I've not used this particular chip before, suggest that like other chips I've seen that it is true that it does not support ISO7816-4 because it is not designed to work at that high level protocol level.
If you look at the picture it's working at the "protocol" level which is one level below ISO7816-4 which is fine, it can transmit/receive data at the NFC A/B protocol level but it is up to the Host's CPU to decode the raw frame data in to ISO7816-4 commands and data.
But this is not your problem, even at the lower protocol level it does not seem to be able to handle both sides on the communication.
I suggest you read https://stackoverflow.com/a/65659726/2373819 as it give some background to hardware capabilities, as the datasheet says it's "Operating modes supported:– Reader/Writer" then it is only an "initiator" and I see no signs that it can be a "target" and therefore it cannot emulate any Tags.
So in short that hardware is not capable of emulating any type of NFC Tag
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I'm trying to interface a board level USB camera with a STM32 family microcontroller and send the image file to a central computer using CANbus. Just want to know if this is possible/ has been done before and how involved a task it would be.
I worked at a company where we sent live (low-resolution infra-red) video streams over CAN, but towards the end of my time there they shifted towards ethernet.
So it is possible, but certainly not what it is best suited for. The main advantages of CAN are that it is a multi-point, multi-master bus with built in arbitration. It is meant for short packets, typically 8 bytes (CAN FD allows you to increase that).
If your camera is USB, why not just get a USB repeater cable or USB-over-ethernet gateway?
If there is already a CAN network in place that you are piggy-backing onto then you need to consider what impact you will have on the existing traffic.
If you are starting from scratch then of course CAN will work but it would be an odd choice.
Depending on if its CAN or CANFD (Affects the maximum bulk transfer packet size) you have higher level protocol options to packetise your images and send them over canbus like any other block of data.
For just reguarlar CAN your after part of the standard called J1939.21 Data Link Layer, there are public versions of this floating around online, however due to the agreement when purchasing the standard, I am not able to share the specifics from what I have.
Its on pages 27-28 of the 2001 revision.
I am looking for a wireless communication technology for exchanging data between devices via sound in ultrasonic frequencies.It is possible to communicate with two mobile devices.I want to communicate a mobile and an embedded device.Is it possible?Any device is working with this protocol?
Of course it is possible. Back in the 1970's my TV remote control used ultrasound to change the channel and turn the TV off. The control was somewhat rudimentary IIRC a short press changed the channel up and a long press turned the TV off. It worked quite reliably for these functions.
Providing more functionality would require a more complicated modulation scheme which, as has been said in another answer, would be prone to interference from other sound sources. This probably explains why infra-red communucation signals are used in more modern remote control systems.
It is possible - why shouldn't it be? Smartphones are just embedded computers too. I imagine getting CE/FCC/etc certifications with such an embedded device will not be so easy. And production testing ...
But is it feasible? Probably not. Power consumption is a lot higher than with any RF-link, it's more susceptible to noise (quite literally) and the required components (microphone+speaker) are bigger than RF-components (antenna).
And then there's a whole bunch of other things you need to keep in mind when working with ultrasound, starting with the plastic design of the embedded device. But also things like the effect of ultrasound on people and their pets etc.
I have a custom ps2 keyboard(8x8 matrix) interfaced with AT89C51ED2 microcontroller, now I need to change it to USB interface. I have been studying about the basics of USB HID class communication(USB HID class specs, USB complete, Beyond logic) and have come to know little bit about the theory behind it.
But I am not able to understand the firmware part, I read a demo keypad application by Microchip which had given a sample source code, but I am not able to understand in the code how data(key pressed) is sent to the IN endpoint and how the host reads that through polling. I know that endpoint is a buffer from which data is sent to host, but Is it one of the registers of the micro-controller and how do I use it in my code?.
And I have been searching the suitable micro-controller with USB support, but no supported demo's are available, any suggestions will be helpful
The AT89C51ED2 datasheet does not mention hardware support for USB, so the answer is no: an endpoint does not correspond to a hardware register. Instead, an endpoint would refer to some software buffers in the RAM of the chip, and some data to keep track of the endpoint's state. Every bit of every USB packet must be handled by the firmware of the device, and endpoints are an abstraction that live entirely in the firmware of your device.
Note: I am assuming that the keyboard doesn't have some kind of USB interface chip, and that the data lines of the USB cable connect more-or-less directly to the microcontroller.
If you can't find the source code for the keyboard, you might look into using an open-source AVR software USB implementation. Here are some useful links:
https://www.obdev.at/products/vusb/
http://www.fischl.de/usbasp/
Please note that you are undertaking an advanced project, and if you are not familiar with AVRs, USB, microcontrollers, reverse engineering, and embedded development/debugging, it might be useful to start with something simpler first.
I want to write a usb touchscreen kext for usb touch screen .
I have read the Kernel Extension Programming Topics and the I/O Kit Fundamentals etc,
My question is,
1 . how to get the input report messages from touch screen ?
2 . how to post the coordinate info to system ?
I have no idea, anybody help?
It depends on the hardware; moreover, this question is quite broad - you'll need to be more specific in your question to get more specific answers. I'll try to provide a broad overview:
A touchscreen has 2 parts:
Output: showing the image coming from the computer on the display
Input: the touch events to feed back into the computer
As you haven't asked about (1) at all, I assume your device just plugs into a display port on the Mac and is already displaying correctly. If not, you'll want to look into the IOFramebuffer API.
For (2) - Pretty much all USB input devices are HID devices of some form. If you're new to HID in general, you'll probably want to read and understand the USB HID specification and related documentation as you'll be using that information throughout.
OSX already comes with comprehensive support for the standard HID device classes such as keyboards, mice, touchpads, graphics tablets, etc. If your device claims to be any kind of HID device, OSX should already be detecting it and attaching its generic HID driver to it. You should see a IOUSBHIDDriver instance in the I/O Registry (eg. using Apple's IORegistryExplorer tool, or ioreg on the command line).
I'd also expect your device to conform to HID's absolute pointing device profile, so at least single touches should already be working properly. If it's a multitouch device, or you need other extra features, you'll probably want to implement a IOUSBHIDDriver subclass that generates or converts the necessary multitouch events.
If your device for some reason isn't already a HID USB device, you'll need to write a custom USB driver for it, and convert the events coming from it into HID events, as the HID events are passed directly into userspace and processed there. You can actually write USB drivers and generate HID events from userspace, so you might be able to avoid writing any kernel code at all if you prefer.
Apple provides some documentation on HID:
The HID Class Device Interface Guide covers some general concepts and the userspace interfaces.
The Kernel Framework Reference has API documentation for the various IOHID* classes in the kernel.
If you're going to be writing your own kernel HID device driver, your best bet is probably the IOHIDFamily source code. You can probably also find some open source examples around the web.
Apple's USB mailing lists is probably also worth checking, both for the archives and if you have questions. The darwin-kernel and darwin-drivers lists are also relevant.
I'm looking to control a mains powered light from a simple relay switch connected via USB to the computer.
The relay switch isn't even a USB device, it's just a simple switch that requires the USB voltage to turn it on. When the voltage drops below a threshold, the switch will turn the light off.
My problem is that I can't control the power output of a USB port. I'm happy to do it using any language on Windows or Linux (but preferably Java because I'm used to it).
Unfortunately, in most cases you cannot control the power supply to the USB port. The power supply is usually hardwired through, and not switchable in software. You can send a reset to a USB device, but that won't work in your case.
There are a number of projects on instructables that do similar to what you describe, but unfortunately they seem to either be quite complicated or require expensive parts.
EDIT: There is actually a product currently in the news which would do want you want, but it doesn't appear to be shipping yet: http://www.pwrusb.com/
EDIT (again): Apparently you can do this with some usb hubs. This post sugggests the Linksys USB2HUB4 is one that works.
EDIT (and again): Apparently there are a number of similar questions, but there don't seem to be any more useful answers:
https://stackoverflow.com/questions/405269/custom-usb-device-that-disables-power-to-usb-devices-plugged-into-it
Power off an USB device in software on Windows
Is there software or code to alter USB power output
Can I write a program that swiches USB on/off
Most of the USB to Serial or USB to RS232 $10 converters support hardware handshaking. Use one of those as a single channel digital io.
Connect your transistor that will drive the relay to DTR on the converter board and command DTR ON/OFF with the converters driver.
A 2N7002 is a good transistor to use (FET actually) since it will work from 3V and doesnt need any resistors anywhere.
Here is a complete solution.
It uses an Arduino board, with a USB connection, (and Uno for example) to control the relay and combines this with pfod (Protocol for Operation Discovery) www.pfod.com.au which will let you control the board/relay from either the Arduino IDE SerialMonitor, or a terminal window (TeraTerm) or a Java program. The message protocol encloses commands in { }, think simplified html for micros, and provides numerous screens, menus, sliders, text and numeric inputs, etc. A detailed protocol spec is available
See Garage Door Remote for a detailed example, with full Arduino code and an example of controlling the relay from TeraTerm as well as the Arduino IDE SerialMonitor.
There is also an Android app, pfodApp, which will do general purpose control via bluetooth, or wifi/internet with 128 bit security. The pfodApp does all the Android stuff, you only need to code some simple strings in your Arduino code to get any menu system you want. See www.pfod.com.au for numerous examples.
You need a USB-GPIO microcontroller:
Adafruit FT232H (about $15)
Arduino Nano ATmega328 (about $7)
See this answer
I would suggest placing a separate Raspberry Pi unit with a wake-on-lan feature activated so you can ping it off and on.
You could do it by combining these two products from Pololu, for about $25:
Micro Maestro (assembled)
Basic SPDT Relay Carrier with 5VDC Relay (Assembled)
The Maestro is mainly a servo controller but you can set any of its channels to be simple digital outputs instead. The output can be controlled from the Maestro Control Center software or you can write your own software. A digital output from a Maestro is suitable to turn on the relay on the relay carrier. The relay could be powered from USB through the Maestro; I think it draws about 100 mA of current so that probably will not be a problem for most USB ports, though it would not be USB-compliant because the total current drawn by the Maestro and the relay would be over 100 mA. You could supply your own power source for the relay if you are worried about that.