Most recent build cannot access P532 via UART on Raspberry Pi 3

[eecharlie]

I've found that commit 14f48d0 (the last one I happened to use before this problem occurred) does work, but latest 216145f does not.

The specific failure is no ACK signal back from the PN532 after power-up command is issued. Intermittently I see an unexpected PN532 response message. I suspect a timing issue which may be addressed by something like the patch on the wiki for the PN532 Arduino Shield (note I am NOT using that, I'm using the Adafruit NFC Breakout with direct UART connection to RPi).

I notice that there have been no changes to pn532_uart.h/c in the last year. So, I am stumped.