I have a low power application where I need to read RFID tags. I purchased the Adafruit PN532 breakout board to develop the code and it works fine, but the board is physically too big to use in my prototype. I purchased the Grove NFC and the code I wrote works fine with it, but there doesn’t seem to be any way to put it into a low power mode between tag readings.
I actually had written code to control the reset pin to put it into Hard-Power-Down mode, which is 2 uA. Unfortunately, the Grove board ties this pin high and there’s no pin realistic way to access the pin. The Soft-Power-Down mode is 45uA, which is OK, but I can’t figure out how to assert that mode. I can do it with the Adafruit board, but it doesn’t work with this board.
Anyone know what the magic command is or where I could find additional documentation?
Forgot to mention I’m using I2C.
I’m starting to think this isn’t necessarily a software problem. I removed all connections to my host board and simply connected power to the NFC board. It defaults to 36 mA. Then I shorted the pin side of the pullup resister connected to the reset pin. That should do a hard power down to 2 uA plus the current through the pullup, which is 10K Ohms, so another 100 uA. Instead, it goes up to 60 mA.
I’m definitely missing something.