Should the PN532 oscillator work at the start?

[dominusdrr]

Hi.

I made a prototype based on the following board:

http://www.playrobot.com/robotpress/wp-content/uploads/2015/08/PlayRobot_CSR0002_PN532-NFC-RFID.pdf

I tried to communicate via RS232 with PN532, but I don't get any response. Check the connections and voltage levels and everything seems fine, except that I don't see the oscillating voltage at the terminals of the crystal with my oscilloscope.

I read that at the beginning the device is in low power consumption. Should it be normal in the absence of oscillation?

Thanks in advance for any comments or suggestions-

[KirillT]

Dear Kan,

You posted one page from the datasheet and said that it's necessary that Vbat must be greater than 3.4V to supply PN532. But there are other sheets of the same datasheet, which show the possibility to use this IC with lower power voltage:
p4: VBAT battery supply voltage 2.7 - 5.5 V
p86: diagram with LDO offset which shows possibility of generating DVDD from Vbat as low as 2.5V

p194: Supply voltage of VBAT below 3.3 V reduces the performance (e.g. the achievable operating distance).

At the same time if take the worst case scenario from the (p.195) Power management characteristics (LDO offset max = 0.7V and Reset threshold on DVDD falling max = 2.6V) any voltage lower than 3.3V on the VBAT can cause Reset and switch off condition.

To sum up it's a bit ambiguous. So could you kindly advise if it is possible to work with PN532 with 3.2 - 3.4 V input voltage range on the VBAT input? And if no, is it possible to switch off LDO offset in this case? It looks like with switched off LDO offset, 3.2 - 3.4 V on the VBAT should be enough for all scenarios.

Thank you in advance!

Best regards,
Kirill

[Kan_Li]

Hi Fabian Romo,

PN532 is a NFC controller which means there is a MCU core inside, so oscillator needs be available.

Have a great day,
Kan

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[dominusdrr]

Hi.

Of course there is a crystal connected to the PN532.

I bought the aforementioned board and the problem was the same, but looking and searching I found this in google:

https://forums.adafruit.com/viewtopic.php?f=25&t=113742

The communication frame to enter normal mode is as follows:

0x55 0x55 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xff 0x03 0xfd 0xd4 0x14 0x01 0x17 0x00

With this kit that I bought has already responded, however my prototype still does not respond. I think it's because the kit works with 5 V and that way it can generate the 3.0V of the internal regulator. While my prototype works with 3.0V and that I think is insufficient for the internal regulator of the PN532 to generate 3.0V. I think that is my mistake.

Thanks

[Kan_Li · Accepted solution]

Yes, that might be the cause. Please note Vbat must be greater than 3.4V, please refer to the following for details.

Hope that helps,

Have a great day,
Kan

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[dominusdrr]

One solution could be to not use the voltage generated by the chip and use the 3.0V of the system.

[dominusdrr]

An additional question Is it necessary that the antenna is connected to the system so that the crystal oscillates?

[Kan_Li]

No, there is no relationship between them.

Have a great day,
Kan

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