Time to push some buttons! (Seeing the demo script in action)
Using our “multicast” capability, here we use the preloaded SNAPpy script
“McastCounter.py” to show that all three nodes can talk to (and hear) each other.
Press the select switch on the SN111 End Device Demonstration Board or the SN171
Proto Board. The seven-segment display on the SN111 should now be showing “01.” The
SN171 Proto Board and the bridge device receive the count as well, but have no seven-
segment display to display the change. Instead you can watch the lower two bits of the
count displayed on LED2 and LED1 on the SN171, and as a cycling tri-color LED on the
SNAP Stick.
Each additional button press should advance the displayed count by one (wrapping
around to 00 after the maximum value of 99), regardless of which node’s button you use .
Press the button on the SN171 Proto Board node to see it advance the count as well. (If
this does not function as expected, check the S1SEL jumper on the SN171 to be sure it is
connecting the GPIO5 pin rather than the RESET pin.) Turn off the SN111 End Device
board, and then turn it back on. Notice that it is now displaying 00 on its seven-segment
display. Press the button on the SN171, and the SN111 will now display the new count.
Press and hold for two seconds the push-button on either of the nodes to reset the
count to zero. The node with the seven-segment display should now show “00”.
Unplug the SNAP Stick from the USB port. Press the buttons on the remaining nodes.
The displayed count on the remaining nodes should still increment with every press of the
Select button.
The “bridge” node can provide the eventual connection to the Portal PC, but it is not a
“coordinator” of the SNAP network. (there is no central coordinator with SNAP)
Plug the SNAP Stick back in if you want to see all three nodes interoperating some more.
Some things to notice:
The nodes are immediately able to communicate with each other:
There is no such thing as a “network join time” with SNAP.
Any node can talk directly to any other node:
There is no central “coordinator” node with SNAP.
Using SNAPpy scripts, SNAP nodes can autonomously respond to changes in their
environment:
Page 16
of 42
EK2500 Users Guide-v1.7