TRF7960 EVM

Hi Walter,

This will be tough to accomplish, but may be feasible.  We do have an app note for a 4W TRF7960 power amplifier.   

http://www.ti.com/litv/zip/sloc132

2 feet range will be difficult depending on the tag size.  What size tag will be used?

Reading 100 tags simultaneously at 2 feet will also prove to be a challenge.  Will all 100 tags be at 2 feet range?  As more tags are introduced into the field, the range is reduced as each tag much use the energy to power up.

Will this be a high speed application?  How long will the tags stay within the antenna field? 

Is the orientation of the tags known?  Are the tags mounted to an object?  What is the material of the object? 

If the reader volume is not too large, it may be worth considering some of the off shelf type solutions.  See the Feig LR2000 reader and antenna solutions.  This is a really great high power reader(up to 8W) and is well known in the RFID world. 

LR2000: http://www.feig.de/index.php?option=com_content&task=category&sectionid=12&id=52&Itemid=127

LR Antennas: http://www.feig.de/index.php?option=com_content&task=category&sectionid=12&id=54&Itemid=130

Please provide some more details of your application and I will evaluate feasiblity.  Thanks! 

Best Regards,

Eddie LaCost

The application is replacing optical product codes (like when shopping) with RFID tags so that you can walk through an antenna gate and all your products be scanned. We expect difficulties with some products, but we want to get as close as possible. The products will be distributed throughout the field of a cart's size (~3 feet wide, 4 feet long, 3 feet deep).

This is a very difficult application that I do not see a solution to currently. 

1. Metal cans will be difficult to tag due to the detuning effect.

2. Tags could potentially be laying on top of each other or in very close proximity.  This causes mutual detuning effect.

3. At HF(13.56MHz), using the magnetic field, long range is difficult. 

4. Tag cost is too high to tag everything(ie. pack of gum).

5. Customers could easily shield tags with foil or other metallic material and go through a portal without paying for some items.

6. Tag orientations are unknown.  This means larger antennas and higher output power must be used.  This still may not capture 100%.  When a tag is in worst orientation(perpendicular to loop antenna), read range can drop by 50-75%.

Honestly, I do not see this is as a feasible application at this time.  This application has been discussed since RFID has become mainstream, but has not never been implemented succesfully that I know of.  It is very unlikely that this could be implemented succesfully with HF(13.56MHz).  Passive UHF overcomes the range requirement and tag cost to a degree, but is more susceptible to metal and liquids.   

Is this for a customer application or a research project?

Best Regards,

Eddie LaCost

This is for a research project for an undergraduate senior level design class. We're expecting to have to make changes, but we must implement the system to some degree.

Thanks for the info.  I would really suggest looking into Passive UHF EPC Gen2 for this application.  Unfortunately, TI does not currently offer any Gen2 products.  The UHF electric field coupling is better suited for long range and large tag density high speed applications.  There will be significant design challanges as discussed earlier. 

I wish you the best of luck on your project.  Let me know if you have other questions.

Best Regards,

Eddie LaCost

Mr. LaCost.

Good day.

About the antenna´s matching in the trf7960, what is the reason for the resistance of 0 ohms, which is between the antenna connector and the rest of the circuit? i can not see the point.

Thanks

In the TRF7960EVM, the purpose of R3 is to allow for use of an external antenna.  Remove R3 and the on board PCB antenna is disconnected and the signal is routed to J3. 

If you want to look at the characteristics of the on board PCB antenna, remove R3, add R5, and remove R4.  You can then use a network analyzer to peer into the on board PCB antenna from J3. 

Best Regards,

Eddie LaCost

Mr. LaCoste, thanks a lot for your information, i hope you can help me with something else.

I´m using as guide the TI ccs code in the document  203, as I am loking C language again after a few years, I have no clear this line of code:

  * PBUF = (0x1f & * PBUF) / * register address * /, 

which is in the WriteSingle function, in the   parallel.c, file, What is  the reason of the AND operation? and why to take only 5 bits, if the address and commands are organized into 8 bits according to the document.

Thanks.

The AND operation here is adding 1F with PBUF data. 

This is only 5 bits because this is a "write single" command.  See table 5-31 in the datasheet.  Bits 5-7 are all zeros to indicate address, write, single (not continuous). 

Best Regards,

Eddie LaCost

We finally have another questions for you Eddie :)

We've got the source code to compile and we have a decent understanding of how it builds the tag command and sends it to the board. We need to basically create a simple GUI that allows inventory and read single block commands. We assume in general what we need is the initialization code for the hardware and then just the commands to send. Could you give us any tips on how to create a much more basic piece of software with just this functionally?

Walter,

Please see the app note below that describes the ISO 15693 host command protocol for the TRF7960 EVM.  You can also obtain the needed command strings by using the GUI and looking at the strings in the log window at the bottom.

http://www.ti.com/litv/pdf/sloa141

Best Regards,

Eddie LaCost

We were already fairly clear on how to generate and send commands, but we're having trouble setting the port and protocol in our own software. We've been looking through the GUI source and modifying it in order to figure out how it works, but we're at a loss. We need to figure out how to open the port using createFile properly. We want to hardcode our software to open COM3 and set an appropriate protocol which we think we've done by simply using send(0).

We're terribly confused by the structure of the sloa GUI. We can't determine what function is called when "Select Port" is clicked. We thought it was OnButton1, but we've put a breakpoint in the code there and the software doesn't stop when we click the button.

does TI sell this kind of power amplifier for TRF7960 EVM, Sloc 132?

I need to make antenna that has a reading range of 1m. Is this possible if i use trf7960EVM + power amplifier?

Thank you.