PN532 Unresponsive After One Successful Scan

[Ben B]

My setup:
Raspberry Pi 2 running Raspbian with a PN532 Breakout Board connected using the USB to FTDI cable sold by Adafruit.

Success case #1:
Using NFC Tools version 0.10.0, running tagtool.py, I am able to successfully read MIFARE Ultralight C tags.

Example:

 $ python examples/tagtool.py --device tty:USB0:pn532
 [nfc.clf] searching for reader on path tty:USB0:pn532
 [nfc.clf] using PN532v1.6 at /dev/ttyUSB0
 ** waiting for a tag **
 Type2Tag 'NXP NTAG213' ID=04C461224B3F80
 NDEF Capabilities:
   readable = yes
   writeable = yes
   capacity = 137 byte
   message = 3 byte
 NDEF Message:
 record 1
   type = ''
   name = ''
   data = ''

Success case #2:
If I **downgrade** to version 0.9.2, I am able to successfully read MIFARE Ultralight C tags, using a script as follows

 import nfc

 def on_connected(tag):
         print(tag)

 clf = nfc.ContactlessFrontend("tty:USB0:pn53x")
 clf.connect(rdwr={'on-connect': on_connected})

Note the use of the pn53x driver, not sure if that's significant.

Failure Case:
If, however, using nfcpy 0.10.0 I try to run the same script above except with pn532 in place of pn53x, I am able to read a tag successfully exactly once.

 pi@raspberry ~/nfcpy $ python test.py
 Type2Tag 'NXP NTAG213' ID=04C461224B3F80
 pi@raspberry ~/nfcpy $ python test.py
 Traceback (most recent call last):
   File "test.py", line 6, in <module>
     clf = nfc.ContactlessFrontend("tty:USB0:pn532")
   File "/home/pi/nfcpy/nfc/clf/__init__.py", line 72, in __init__
     if path and not self.open(path):
   File "/home/pi/nfcpy/nfc/clf/__init__.py", line 146, in open
     self.device = device.connect(path)
   File "/home/pi/nfcpy/nfc/clf/device.py", line 104, in connect
     device = driver.init(tty)
   File "/home/pi/nfcpy/nfc/clf/pn532.py", line 366, in init
     if (transport.read(timeout=100) == Chipset.ACK and
   File "/home/pi/nfcpy/nfc/clf/transport.py", line 127, in read
     raise IOError(errno.ETIMEDOUT, os.strerror(errno.ETIMEDOUT))
 IOError: [Errno 110] Connection timed out

After this happens, tagtool, the script in success case #2, and nfc-poll are all also unable to read tags from the PN532 until I unplug the USB to Serial adapter from the Pi and plug it back in.

[Ben B (benberry)]

This may be related to the apparent regression in Florian's 2015-09-19 post here https://answers.launchpad.net/nfcpy/+question/237349 .

[Ben B (benberry)]

Fixed on v.0.10 by adding `clf.close()` to the end of the `on_connected()` method.