Using RC522 RFID with ArduinoUNO Original

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Hello,

I am new in this site,

I want to use RC522 RFID module, equipped with NPX chip. It will be connected to Arduino UNO that works al 5 VDC.

I have read the NPX datasheet, end in pages 74 and 75 it clearly specifies the chip is not 5 VDC tolerant.

I do not have active mosfet voltage shifters, so I must connect with passive R voltage dividers.

I suppose that from the five comm lines, only four are read by the RC522 3.3 volt slave module.

So,

SDA
SCK
MOSI
RST

Need to be connected via voltage divider resistors, for instance 510R to the line then 1K to ground, to shift down from 5 to 3.3

The fifth line (MISO) is at 3.3 volt in the slave, but this can be connected directly to the PIN12 in UNO, as it will read 3.3 volt as a HIGH condition.

Is this scheme right ?

I want to get some help before frying my 522, I am 420 km far from a dealer to replace it ?

Thanks so much
Horacio

Kind regards,
Horacio

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I have used in the past resistor divider and it worked. On your Arduino UNO you have 3.3V so be sure to power from the 3.3 V source. Also add some resistor on the data and clock lines, usually if you use 1k and 2k resistor you should obtain the needed value of 3.3 V.

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Thanks Nikel1992 !
 

What I want to confirm is the names of the Lines which should be down shifted.

In my knowledge the lines which require down level shifting are the outputs of Arduino at 5 Volts:
 

SDA
SCK
MOSI
RST

 

The MISO line can be connected directly.

Am I right ?
Thanks again,
 

Kind regards,
Horacio

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Sounds right to me, although it will not hurt to add a 1k in line on the input of the miso pin so a mis programming of that pin to an output will not damage your module.

best to be safe.  
good luck with your project 

 

jim

 

 

 

 

 

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Hello,

I tested again, with two different wirings:

Using 1k resistors in the four lines

Using passive dividers to shift down outputs from Arduino to 3.3 Volt.

Still same errors.
I ordered new RC522, mine is perhaps fried.

I will come back when solved, and inform the final solution.

Thanks for your help
Horacio 

Kind regards,
Horacio