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I2C and UHF RFID conflict need explainations

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BiNa2605

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Hi everyone,

I used UHF RFID tag to measuring sensing signals. I have a question.

When I measured I2C signals, not using RFID reader to transmit RF wave to the tag
tek00012.png

And this is when I used UHF reader to transmit RF wave to the tag, the distortions appeared during capturing.
tek00015.png

Anyone can tell me why? I appreciate for that.
 

Pullup resistors with high values ?
I2C routed in a spread path ?
PCB not sufficiently grounded ?
 

RFID takes a lot of current. Poor grounding, more capacitors needed. Show your pcb design first.
 

I've just tested only the oscilloscope, it has the same problem

Not have RF wave propagation
tek00016.png

Have RF wave transmission
tek00017.png

This is my PCB
i2c ccs811.jpg

I connected a sensor to testing, so I made 4 wires to extend board, SCL, SDA, VCC and GND as shown in the above picture.

@andre_teprom
Pullup resistors with high values ? ==> I used 10K resistor to pull up
I2C routed in a spread path ?==> My English is not good, could you explain me more detail about that.
PCB not sufficiently grounded ? ==> I check with Muliplier, it is connected well.
 
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I don't see any capacitors. And you do not understand what grounding I'm talking about. It is impossible to check with multimeter. Forget, dude, this will never work.
 
At the above picture it is not clear what is connected to what. Anyay, I2C is not suited to interconnect boards appart like that. You should reduce the length of the wires, as well as to twist them along with a gnd wire, just to act as a 'shield' for induced EMI noise. As a further attempt, you could try reducing the pullup resistors and reduce the I2C clock rate, which wasn't also mentioned so far.
 
@Easyrider83: Could you please explain me more about what grounding that you mentioned. I have only one 4.7uF capacitor from vcc to ground, it is designed based on the datasheet.
 

Before start making your own design, review at least few of them done by proffessionals. Open you PC at look at the PCB. You will see solid poligons for grounding and a lot of capacitors around all chips to reduce noise over supply voltage.
 
Yes Sir, when I adding more capacitors and reduce the length of wire. The problems are solved.
 

Yes Sir, when I adding more capacitors and reduce the length of wire. The problems are solved.

for bypass caps with Rf involved, you want a high value, such as your 4.7uf and a low value, like 0.01uf in parallel.

But the issue I think I see is pick up from your scope probe. the shorter you ground wire from your probe, the better.
 

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