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I have connected a NXP NFC Module (pn7120) over I2C to i.MX6 Board.

I tried to check whether the device is detected in the i2c probe command. It didn't detect in the first call, but got detected in the second, third time failed and fourth time success. What does this mean.. How to solve this.

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  • \$\begingroup\$ The first thing I would check is if the crystal oscillator is working properly. You may also want to check with an external clock. \$\endgroup\$ – Janka Mar 23 '18 at 11:06
  • \$\begingroup\$ wait what ... you're working in /usr/lib while logged in as root? \$\endgroup\$ – Brian Drummond Mar 23 '18 at 13:05
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The PN7120 is normally in a low power mode. In the datasheet it says that the chip has "wake-up on address only". You need to first send it just an address only I2C transaction to wake it up, and then quickly send actual I2C transfers before it goes back to sleep. Sending two i2cdetect commands close together simulates this. See this thread for someone who was having a similar problem.

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