ThingMagic Mercury xPRESS Platform v1.7 - Manual (Page 27)

RFID Sensor Application
A D I V I S I O N O F T R I M B L E
Using the Sample Application 27
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RFID reader task
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Keyboard output task

EPC formatter function
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Custom drivers: Bluetooth module
These functional utilities interact with each other as shown in the diagram below:
Demo App Program Flow
Execution starts at xpressReader/app_demo/main.c, which launches 2 tasks:
RfidReader and KBWedge.

Task RfidReader runs task_rfid, which controls the reader.

Task KBWedge runs task_wedge, which controls the UI (keyboard output,
pushbutton inputs).
The workflow begins when the user presses the read trigger button

pin_edge_handler fires on the falling edge of the button press, having previously
been set up by wedge_configure_buttons, which was called in task_wedge’s
initialization.

pin_edge_handler reads the current state of the read trigger button and sets the
global activateTagReads accordingly.

task_rfid monitors activateTagReads. When it becomes true, it enters readTags.

readTags operates the RFID reader then calls reportTags to retrieve the tag
reads.

reportTags fetches each tag read, formats it, then adds it to epcQueue

task_wedge constantly runs wedge_ui_process, which executes the state machine
that generates USB HID keyboard output. This has to be written as a state machine
because the USB host polls for one HID message at a time, and each HID message
corresponds to a single keypress (or release.) Note that only low-speed USB
connections do not poll automatically, so task_wedge’s inner loop only needs to run
in that case. For faster USB modes, the USB driver calls wedge_ui_process
directly.