You typically don't use RFID for communication between two computers -- you'll use WiFi or Bluetooth or a regular RF channel for that.
For read/write RFID (with "cards") you can use 125 kHz (not MHz!) if you want a cheaper version, or 13 MHz if you want the ISO standard which may be a little more robust.
I don't know a good RFID hobbyist community. That doesn't mean there isn't one. What does Google say?
I dont want to use RFID st8uff for anything computer to computer related.. purely Arduino based.. and using the RFID stuff to make things happen or log..etc..
I want to be able to READ & WRITE to cards.. I think the one you provided only does read?
Still no sure why would want or choose 125kHz vs 13.56Mhz
I dont want to have to buy another RFID kit later because I didnt get one that writes.. or (whatever).. so Im trying to explore these options with the community here.
Also not sure what the UART interface is? and what the difference is? between this UART and another protocol?
(on a side note, I got my pcb's from iTeadstudio.com the other day.. I think they came out great!)
UART means serial port communication. Other interfaces might include I2C, SPI, USB, and some custom bit-banging protocol. UART should work fine with SoftwareSerial, so you don't need to use the hardware port.
125 kHz, 13 MHz, 10 GHz, .... all the different frequencies might have different trade-offs, but for learning, I would probably just buy on price. If you don't trust the iteadstudio stuff, there are tons of hits on Google, and I wouldn't know how to tell one from the other. There are also a large number of eval boards and circuits on Digi-Key. The only thing I'd make sure of is to make sure to get tags from the same place as the reader/writer, to ensure they are compatible, but not every kind is compatible in the same frequency (although allegedly most of the 13 MHz band ones follow an ISO standard).
If you try anything in particular, please post back how it goes, 'cause I'm curious too
With 125KHz RFID you get reading only although there is a type of card you can write to this is only to write a 64 bit serial number.
The so called smart cards at 13MHz can be the read / write type. Typically they have a serial number which is fixed and an area of read / write memory typically one or two K in size. As these are designed for electronic money transfer these areas of memory are normally protected by encryption keys, although you can set your own if you just want to store data on them. In some applications the data from a finger print scanner is stored on the card as well and can act as a secure ID system.
So if you want to play get a smart card kit.
RFIDs of higher frequency can also be used but these are very expensive, can have a long range and can handle reading multiple tags in a field. That can be done at the lower frequencies but it is a bit of a fudge. At UHF frequencies you can read up to one hundred tokens in the same field quite quickly.
thanks for the reply.. that was a perfect 'quick start'!
another question, is the MiFare cards?
I have read conflicting articles..
are these only usable with certain reader/writers?
Im looking for the most versatile.. if i get a 13Mhz reader/writer.. I wanna be able to, or at least understand my/any restrictions, use cards from different places, instead of having to buy a proprietary card if avoidable
being able to read/write from far away and multiple cards are all 'very' attractive features.. but if it makes that type of set-up alot more in cost/price... than I think it probably best left for a real/specific project that has those needs.
I'm off to re-search RFID kits and prices based on everything shared above.
A MiFare card is a brand or type of smart card working at 13MHz, it is perhaps the most popular card of this frequency (13MHz). It has space to store data as I said before.
are these only usable with certain reader/writers?
Yes most cards need their own reader so that the physical interface and the software protocol it uses matches.
being able to read/write from far away and multiple cards are all 'very' attractive features.
Yes it is but it adds complexity and cost to a reader and I have not seen a reader that will read any card there are just too many and it is very easy for someone to invent their own protocol. I know I invented several myself when I designed RFID readers. Most 13MHz readers can read the ID number from many different cards but after that reading data is different as is writing data.
I have a qestion abotu the TYPE of reader/writer to purchase.. (the protocol/format)
I saw UART mentioned above (which is serial?)
but I also see many more touting the SPI interface/protocol instead?
Is one better or preferred over the other? I see lots of SPI devices/chips? but myself am unclear as to why I would/should pick UART over SPI? (or whatever)
but I also see many more touting the SPI interface/protocol instead?
Odd I see more of the serial type.
With the serial type you have to use a UART emulator like New Software serial, these are not too good. With SPI it is faster and does not use up the serial resource. However is it a SPI master or slave as only a master can initiate communication.
I've been learning how to use one of these rfid reader/writer and getting good results.
I use softwareserial at 19200. I am currently looking at how to connect to the cards SIG pin, docs say it has an Interrupt output, LOW level indicates Tag in the field.
Which means you don't have to keep polling the card to see if there is a Tag around. There are also write options, which can store data in a purse/wallet area. Not got into that yet.
SPI and UART are different ways to send data between chips. Other protocols to do the same include TWI/I2C and OneWire. They don't have one clear winner. UART is like a PC serial port. Data rate is low, but it's easy to work with. It generally uses two wires, but can use more for flow control. There are exactly two chips (peers) on the "bus." I2C uses two wires, a clock and a bidirectional data wire. Chips as addressed by ID, so many chops can share the bus. Because it's synchronously flocked, it's faster than UART. SPI uses three wires, clock, send, and receive, Plus one chip select ("CS") wire per chip that shares the bus other than the master. SPI generally can run the fastest of these three, but uses the most wires.
Any of them will work with an Arduino for RFID.
(watch it on an actual computer, not a phone or iOS device, so you can see the annotations)
Here is the RFID door system I built a couple years back. I still use it everyday to this day. Only thing in any state of failure is the blue on the RGB led, but it has been on for over two years 24/7 so I guess I can't complain. 125kHz. UART serial connection to an arduino via an ID12 RFID reader (sparkfun).
Terminated all the data/power lines via cat5 so I only had to drag one wire through the cinder block wall.
I got my start on this on instructables via a user who did most the hard work. His handle is "pcmofo" you should look up his project.
I took his project modded the code and hardware to meet my needs and have not looked back. This thing is awesome.
Well you have to pole a slave. That is you have to ask a slave if it has seen a card and it answers you. If it were a master then it would send you data when it sees a card. This is more convenient but tricky to implement because you either have to pole the clock to see if data is being sent or arrange an interrupt to be generated and let an ISR do the receiving.
I suppose either way your code ends up polling something so I suppose it doesn't matter.
Thanks for the link to that reader, it looks good and they ship to the UK (via UK eBay) so I might get one myself as I haven't got a 13MHz reader at the moment.
I have also attached whatever documentation and sample .pde they supplied.
(.pde to long to post here..its in the attachment)
It seems to compile.. and load on my Arduino.. but outside of that. it does nothing. (Im not even sure what the sample is SUPPOSED to do? I thought just wait/poll for a card in the proximity an display the cards details/info?)
I check serial monitor.. and nothing is printed..but it is 'scrolling' like a blank line/carriage return is being printed..
This looks promising. I figured if I subscribed to the thread
and waited long enough, someone would post something
helpful.
I'm in the same boat you are, but I've DLed the code and
now I have something to look through.
One thing I noticed is that there's a disjointed instructions
in where to connect from the Arduino shield to the RFID
card--in one case I noted it needed to go to pins 50-53 (or
thereabouts) and in other sources it mentioned connecting
from the RFID card to the shield's pins 10-13 (or
thereabouts). Maybe these are internally identical, I don't
know.
