ACS ACR122U is an USB NFC reader, PC/SC and CCID compilant, based
on NXP PN532 chip.
Internally, it's build of MCU, PN532 and an antenna. MCU makes the
device CCID and PC/SC compilant and provide USB connection.
In this achitecture, a host cannot talk directly to PN532 and must
rely on MCU. Luckily, MCU exposes pseud-APDU through PC/SC Escape
mechanism which let the host to transmit standard PN532 commands
directly to PN532 chip with some limitations.
The frame roughly looks like:
CCID header | APDU header | PN532 header
(pc_to_rdr_escape) | (pseudo apdu Direct Tramsmit) | (len, TFI, cmd, params)
Accordign to limitations, ACR122U does't provide any mechanism to
abort last issued command.
Signed-off-by: Waldemar Rymarkiewicz <waldemar.rymarkiewicz@tieto.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
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