PN532 NFC low vbat operations and I2C

Discussion created by lpcware Employee on Jun 15, 2016
Content originally posted in LPCWare by rbreitensteinatu@gmail.com on Tue Feb 18 14:59:18 MST 2014
    Ok iv been working with the PN532 for a while to communicate with a MSP430F5659 via I2c.  had alot of issues that got resolved and now i need to put the PN532 into low vbat mode that way it doesn't consume to much current when not being used to do this i thought i would attach the RSTPD_N  pin to the controller and pull it low for at least 20ns then wait 2ms but testing has shown when this is done from I2C it never leaves low vbat mode (my testing by the way).  Does anyone know when using I2C what would be the protocal for entering and exiting low vbat mode as well as answer any questions such as can it notice a card and send some kind of signal to the host controller (from what i read IRQ is disabled in low vbat)  what would be the best way to implement this if cards are read few and far between and preferable the customer wont have to hit a special switch to activate the nfc chip.  either way just being able to place it in and out of low vbat reliably is important to me and any help would be appreciated.