I have a nfc card which supports multiple technologies. (For example NfcA,MifareClassic, ISOdep). I want to understand what technology has been used to write to the tag.
Are these technologies independent? I mean can I use mifareclassic to write some data and use NfcA (or ISOdep) to read that data?
Or these technologies each have their own memory?
I have been reading a lot about this subject last few days but have not found a good reference.
I also did some tests myself. I wrote an android app to write a NdefMessage to a tag. and I found the corresponding data bytes when I used MifareClassic APIs to dump the memory.
I took a look at the code inside MifareClassic library, and found out that all of the relative functions(e.g readblock,writeblock) create a byte array and pass it to transceive(). In android documention it is mentioned that calling MifareClassic.transceive is the same as calling NfcA.transceive.
which is a bit ironic since it is mentioned in NfcA documents that NfcA and MifareClassic are not the same and they have different transmission protocols.
another thing that I realized was that Ndef is not a protocol by itself. it a standard format to store data. apparently Ndef class has different implementations for different tags. on a MifareClassic tag you can only use Ndef class to write data to it if the tag is using the default keys. otherwise you will not be able to write to the tag.
Related
I am working on an ECG module, which is giving out data in bytes. There's a protocol document about it explaining like how to structure the packets, that are coming out of the module.
I want to decode that data.
I am confused whether protocol buffers will help in this or not. Any other methods that would be helpful in this decoding and writing that protocol in Python ?
Protocol buffers only works with its own encoding format.
For decoding a manufacturer-specific custom binary format, I would suggest Python's built-in struct module. Here is a basic tutorial which is easy get started with.
If the manufacturer-specific format is text based instead, you can either use basic string manipulation to split it into tokens, or one of the parsing libraries for Python.
I am a software developer so I have quite a lot of reading to do on hardware. My questions is this :
My goal is to create an RFID tag that has dynamic data. So I plan to use a microcontroller to be the processor and input data to an RFID module. I have did some research on RFID in general, is it actually possible to change RFID/NFC tag values via wiring instead of and RFID writer?
I really hope someone could give me some guidiance on this.
There are commercial ICs available from different manufacturers - e.g. NXP's NTAG I2C or ST's ST25 Dynamic NFC Tags.
You can connect them to your µController and share data to a phone. Most conveniently in the form of an NDEF message, as this can be read by iPhones as well.
Also the other direction (phone to µC) works, e.g. for configuration or firmware upload purposes (restricted to Android).
Commercial rfid tags generally have a manufacturer assigned ID (similar to a MAC address. Additionally, programmable tags have a raw memory that you can directly write bytes into sections.
When you read one with a reader, you'll get back this ID and the byte contents of the section you ask for.
A more typical use would be using the id to access a dataset stored somewhere else. Storing data locally isn't impossible though, you can also get write once types, each memory section can't be overwritten. The accrual memory capacity tends to be extremely small, like long url only.
I am working on a project where we are using protocol buffers to create and parse some of our messages (protobuf-net). This is so elegant, that I would like to use this same deserialization method to parse other messages emanating from external non-protobuf generated sources. Is this possible?
I would imagine that it could be possible to specify all of the .proto fields to be fixed size (i.e. not like variable ints). The question is then whether you could replace the protobuf headers with other magic numbers or whichever header the 3rd party protocol uses.
If this is a bit confusing, an example may shed some light:
Let's say you buy a fancy toaster that exposes an ethernet port. It supports a proprietary but well documented protocol. Can you burn heart shaped patterns on your toast using protobuf?
At the moment, no: the library is tied to the protobuf wire specification; it does not have support for non-protobuf data.
In a way, it is a bit like asking: "can XmlSerializer read/write json?". It isn't something that is on my list of things to look at, to be honest.
I have a very specific problem: I want to write my own DMX-Software to control our DMX-fixtures. Does anyone know a interface to use? It would be great if there would be any Framework for using it, so that I only have to sent the channel and the value to the interface.
I noticed your question was for Mac, but I wrote a Windows specific C++ program, which could probably be easily modified. It's adapted from the C# example on Enttec's OpenUSB website. See:
https://github.com/chloelle/DMX_CPP
There's some really good information & code samples (including a working class that I wrote) here: Lighting USB OpenDMX FTD2XX DMXking
Ultimately, you end up setting byte values (between 0 and 255[FF] (brightest) in a byte array.
It's fairly trivial to implement simple effects such as fades or chases.
You would need to use a USB controller to convert your program's instructions to the actual hardware.
I suggest using a simple iphone application talking to a webservice which then interacts with the hardware.
Code samples above are in c# though will show you how to interact with a DMX controller
Do RFID tags have a "real" processor capable of simple computations? If so, what is the processing power of nowadays RFID processors?
That depends.. RFID is a very broad field.
There are very simple tags that really only send back their ID when activated using a fixed function logic. I doubt many of them are still in use.
And then there are very sophisticated ones that even run programs written in JAVA and have crypto-processors and other funky stuff built in.
One example of this is the SmartMX Mifare card from NXP.
http://en.wikipedia.org/wiki/MIFARE
Note: Don't confuse active and passive tags with processor/no processor tags. A tag is active if it has it's own power supply. That does not imply that it has a processor and vice versa.
They do not. They're just an antenna hooked to a data-providing chip, powered by the external radio waves of a reader.
Neither I do know of any RFID with real processing capabilities. However according to Wikipedia description of RFID "[m]ost RFID tags contain at least two parts. One is an integrated circuit for storing and processing information...".
http://en.wikipedia.org/wiki/Radio-frequency_identification