How to get the Received Signal Strength Indicator(RSSI) from the module RI-RFM-007-B?

MrDragon

Hello there,

I´m doing my thesis at the moment and I'm working with a system composed by a control module (RI-CTL-MB2A-03), a Reader Frequency Module (RI-RFM-007-B) and a antenna (RI-ANT-G02C) .

I want to know, how to get the value of RSSI (Received Signal Strength Indicator) from this system to be able to measure the tag's distance. In the datasheet of RI-RFM-007-B the only thing I found was the RXSS and the RSTP but these are related, in my view, with interference regulation when more than one system is operating at the same place.

I really hope someone can help me cause i'm running out of time.

Thank to you in advance.

Flávio

over 8 years ago

0 Josh Wyatt over 8 years ago

TI__Guru* 90906 points

correct, RXSS- is digital output which changes state when adjustable threshold is crossed by field strength of another reader.

RSTP is a voltage level which indicates the signal strength of another reader...however, since the technology is half duplex, you might be able to see something small on that pin when tag is responding (as the TX is off at this point and would match setup described in the user guide.

you can also always see this (tag response) with an oscilloscope on the antenna.

this document may also be of use to you:

0 MrDragon over 8 years ago in reply to Josh Wyatt

Prodigy 65 points

First, let me thank you for the help you gave me.

I'm going to give it a try on measuring the antenna signal with an oscilloscope but I'm afraid that the signal changes won't be significant enough to make possible the distance differentiation.

In that case can you advise me in: what other system should I acquire to have that RSSI functionality? Or, if there is, a module that I can add to my system to get that value ?

Thanks again!!

0 Josh Wyatt over 8 years ago in reply to MrDragon

TI__Guru* 90906 points

the only thing i can think of at the moment is to share with you the attached. i made this gadget back at the turn of the century to look for interference at installation sites for these readers. Since the tag response at close range is in the >100mV range, you might be able to use a setup something like this and gain up the RSTP signal going into the LED driver. the voltage divider is set up here to evenly space out the level indication and is cumulative; meaning, LED #1 comes on first and as the level gets higher more LEDs turn on. Then you could correlate that back to something which equates to an RSSI.

you said this was for your thesis - are you tied to LF? we do have an HF reader IC with this capability built in (RSSI register in the TRF79xxA devices gives a 3 bit value back out for tag response - pretty much exactly what you are looking for)

Sniffer Schematic.pdf

0 MrDragon over 8 years ago in reply to Josh Wyatt

Prodigy 65 points

Thank you Josh!! realy, thanks!

I am kind of tied to LF for 3 reasons:

1º- tags price, LF tags are very cheap and because I will need tons of them ( If I deliver the project) I have to look at that too.

2º - for what I know, LF tags work better against interference in open environments.

3º -this is the system that I have to my disposal and I don't think I have budget to buy a new system.
Can you tell me how much it costs the system you told me about, depending on the price maybe i can get some funds if I convince the department that I can deliver some results with that system.

PT

Flávio

0 Josh Wyatt over 8 years ago in reply to MrDragon

TI__Guru* 90906 points

for point #1: you might be a little disappointed. LF tags are usually much higher price than HF (there are more materials involved in making them) in fact, its one of the reasons HF tags were conceived, to allow for the unique ID of things with memory storage in an inexpensive form factor (i.e. inlays)

for point #2 - this is true if you are using TI HDX LF tags, they get ~twice the distance of competitive FDX LF tags.

for point #3 - i get it - since you are student - maybe we could sample you some tags since that is the system you have, so you don't have to go through the hassle of getting new system - let me know. I am sure you can make something work out for your concept/thesis - and you can always hit us up here on the Forum again, anytime.

really it depends on how far away you are wanting to read...if you can scale the results appropriately - you might be able to show something cool with this bundle, some small HF tags and a custom ferrite antenna mounted on it ==> store.ti.com/trf7970a-bndl.aspx
can show you how to do that, too.

0 MrDragon over 8 years ago in reply to Josh Wyatt

Prodigy 65 points

Thanks again for your help josh!!

I think the best way for you to tell me if that product you showed me is going to work is if I explain the general lines of the project. I will have an array of antennas (imagine 6 )placed in straight line, side by side, this array is going to stay always at the same hight from the ground (let's say 45 cm ), where the tags will be. What I want is to measure the different RSSI values that each antena is going to send to the reader. That way i can identify the tags's position within the array, meaning, which of the antenas is closest to the tag.As you see, it's not possible to achieve this without the RSSI so I don´t think I will get something with my system.

So do you think i can acheive this with the model you told me? Is it possible to connect that system to a multiplexer and only then to the antennas?

It has to be an RFID system and in the page they say something abou NFC /RFID that's not clear for me.

Is a complete model? I just have to plug-and-play after I get the antenna (in that department I need you help me too) or do I have to buy any additional hardware to make it functional ?

And last, where can i grade the work you're doing cause you are giving me a great service and I think that should be rewarded!!

PT

Flávio Amorim

0 Josh Wyatt over 8 years ago in reply to MrDragon

TI__Guru* 90906 points

Flavio -
see here for how that would look with HF system (which is underlying tech for NFC (meaning NFC = HF RFID), plus two short videos

www.ti.com/.../sloa167.pdf

www.youtube.com/watch

www.youtube.com/watch

these companies offer multiplexed versions of this idea
all in one (low power) from DLP Design (x8 channels)
www.dlpdesign.com/.../lp8c.php

from Feig Electronics (high power)
Reader ==> www.feig-electronics.com/.../id-isclr1002-long-range-reader.html

from Feig Electronics
Mux (x8 channels)
www.feig-electronics.com/.../id-iscantmux-8-channel-multiplexer.html

0 MrDragon over 8 years ago in reply to Josh Wyatt

Prodigy 65 points

Hi josh

In the video (the first one) that you sent me the tags can only be read in a range of a few centimeters (the same says about this reader in the website), so do you think I can read at 40 centimeters (minimum) if I use custom ferrite antennas. I also have to be sure that the multiplexer works with the custom ferrite antennas. If you can guarantee me that, I have green light to go for that system. I'm going to rely on your knowledge if you say that I can read the tags at that distance.(I also need your help in how to buld those antennas).

Thanks again for your help!!

Flávio Amorim

0 Josh Wyatt over 8 years ago in reply to MrDragon

TI__Guru* 90906 points

Flavio -

attached is the sort of read ranges you can expect with different power levels and tag form factors - the reader antenna size (300mm x 300mm) was held constant here:

TI Reader and Tag Read_Ranges_01_31_2008.pdf

0 MrDragon over 8 years ago in reply to Josh Wyatt

Prodigy 65 points

Hi josh

Thanks for all the information that you have been providing me. I just have one final question, I got my hands into a texas midrange reader that was lost in my department. It's a S6350 and I want to know if this system gives me the RSSI information?

BR-

Flávio Amorim

0 Josh Wyatt over 8 years ago in reply to MrDragon

TI__Guru* 90906 points

i don't remember that the RI-STU-6350 (this is RI-STU-TRDC) was capable of providing RSSI info back from tag - that was discrete transceiver circuit onboard being driven by MCU, predating the RI-R6C-001A chip (which has RSSI/FSK output on pin 16), which pre-dated the TRF79xx family of HF reader ICs (which has RSSI register which can just be read out).

Other wireless

Other wireless technologies forum

How to get the Received Signal Strength Indicator(RSSI) from the module RI-RFM-007-B?