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device manual is elechouse V3 PN532

p.e. to connect via HSU (serial) the wiring is:

elechouse PN532         RPi
---------------         ---
GND                     6
VCC                     1 (3V3) or 2 (5V)?
SDA/TxD                 10
SDL/RxD                 8

Similar wiring for I2C

I've found that it works either with 3V3 or 5V but documentation is unclear with respect to voltage. Can 5V damage RPi? elechouse docs say that it has an integrated shift level converter. Thanks

francesc
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1 Answers1

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Feeding 5V into a Pi GPIO will damage and eventually destroy the GPIO and the Pi.

If the PN532 works at 3V3 that is the safest option.

joan
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  • then I don't understand why in [http://wiki.sunfounder.cc/index.php?title=PN532_NFC_RFID_Module#Test_for_Raspberry] it's recommended to connect 5V – francesc Apr 03 '18 at 16:39
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    I'm not going to read a random wiki. If you feel it has given additional relevant information you should have included the information in the question. – joan Apr 03 '18 at 16:47
  • I agree with your answer. Question is that it's a bit puzzling to find well-known sites (the one I cited and others including Raspberry-Pi forum) that say connect to 5V. That's why I was asking in the first place. Perhaps this device has some kind of protection – francesc Apr 03 '18 at 18:08
  • "On-board level shifter, Standard 5V TTL for I2C and UART, 3 .3V TTL SPI". To me that suggests it is okay to use it with SPI but not with UART or I2C. Personally I'd measure the voltage it output if I was planning to use that device. – joan Apr 03 '18 at 18:54
  • @francesc - VCC has little to do with signal (SDA/SCL etc) voltage - connect VCC to 5V, you wont have problems – Jaromanda X Apr 03 '18 at 23:43
  • @Jaromanda X Once asked elechouse for technical support the answer is: HSU/I2C Vcc at 5V, but SPI Vcc at 3,3V. Now I begin to understand: both SDA/TxD, SCL/RxD have level shifters in board (an elechouse PN532 V3 NFC). When connected to a 5V arduino, lines level shift to 5V due to the 5V-connected pull-up resistors. When connected to a 3,3V RPi lines remain 3,3V. So the correct answer is: I2C/HSU Vcc 5V, SPI Vcc 3,3V – francesc Apr 04 '18 at 18:46
  • Fair enough, I hadn't even looked at SPI since the question was about HSU :p - also the wiki in the comment shows that both sets of connections have a 5v and 3.3v pin - as opposed to the device in the question, which just has "Vcc" for both - perhaps I should've looked at the documentation for the actual device, rather than the wiki page (also posted by the OP) which shows a different device based on the same PN532 device :p – Jaromanda X Apr 04 '18 at 23:17