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Sample programs

These simple annotated samples introduce several programmable features for the ConnectPort X2e

ZB, including button handling, LED control, watchdog, RCI callback, and XBee functions.

Button handling

The following sample program demonstrates functions for handling the button on the

ConnectPort X2e ZB.

import select

fd=open('/var/run/reset_button')

(1)

p=select.poll()

p.register(fd, select.POLLPRI)

(2)

fd.read() (3)

while True:

p.poll() (4)

fd.seek(0) (5)

val = int(fd.read()[0]) (6)

if val: (7)

print "Button pressed!"

else:

print "Button released!"

Program notes

1 The reset button is exposed as a Linux file. It can be read to determine the state of the button,

and it is possible to block waiting for the button state to change.

2 To block waiting for the button, the standard Python select module is used. This line, and

the line above, demonstrate how to create a polling object that can wait for button state

changes.

3 Read the current value of the button, but forget it. This is done to “clear” the button and

prepare to wait for its state changes.

4 Rather than reading the button in a loop, the system waits for button state changes using the

polling object created earlier.

5 To read the current value, we first “rewind” to the beginning of the “file.”

6 fd.read() gets pending data from the button file. fd.read()[0] returns just the first character

of that data. int(fd.read()[0]) makes explicit the fact that we expect the character we read to

be an integer.

7 If we read a non-zero value, the button is currently pressed.

Digi ConnectPort X2e ZB User Manual

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