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How to kill a NTag I2c Plus (or stop it)

Question asked by Kai Buechler on Sep 1, 2017
Latest reply on Sep 25, 2017 by IvanRuiz

Hello,

 

I'm using a NT3H2111 (QFN package) and commuincate with it over the i2c interface and a busy bee efm8b2 microcontroller. The NT3H2111 is supplied with 3.3v, has 3kOhm pull ups on sda and scl and 0.1uF capaictor next to its vcc pin. 

At first I did only read 7 Bytes of the config register (address 0x3A) just for testing the busy bee smbus driver. That test reading was running for at least a week or two, while I was working on other stuff. Today I started to develop the communction between the uC and the ntag, so the manual stated  that a i2c read and write config registers always transfers 16bytes. So I changed that from my 7byte to 16 and added a write accees to the config register ( stetting some values in the NC_REG at the config address, remaining bytes are kept to their default values). And this kills my ntag. I killed now the fourth chip, after I read more than the 7bytes and/or start writing the config reg. The chip dies after 4 or 5 times doing that. Looking on the SDA and SCL line then, they both are pulled to gnd when the uC tries to start the communiction. I can still access the ntag with my Smartphone (ndef data), but erase or wirting the config regsiters does not work either after the i2c communictation starts failing.

I measured everything around the ntag on my pcb, there is defenetly no shortcut, and 3kOhm pull ups should be fine also. And the test reading was running for at least a week, like I already stated. 

 

Has anyone faced a issue like that? I'm totally confused.

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