Specifications

SNAP
Channel
900 MHz
Chan. Range
Frequency
Range (MHz)
SNAP
Channel
900 MHz
Chan. Range
Frequency
Range (MHz)
0 1 – 25 902.4 – 912.0 8 33 – 57 915.2 – 924.8
1 5 – 29 904.0 – 913.6 9 37 – 61 916.8 – 926.4
2 9 – 33 905.6 – 915.2 10 41 – 64,
1
918.4 – 927.6,
902.4
3 13 – 37 907.2 – 917.0 11 45 – 64,
1 – 5
920.0 – 927.6,
902.4 – 904.0
4 17 – 41 908.8 – 918.4 12 49 – 64,
1 – 9
921.6 – 927.6,
902.4 – 905.6
5 21 – 45 910.4 – 920.0 13 53 – 64,
1 – 13
923.2 – 927.6,
902.4 – 907.2
6 25 – 49 912.0 – 921.6 14 57 – 64,
1 – 17
924.8 – 927.6,
902.4 – 908.8
7 29 – 53 913.6 – 923.2 15 61 – 64,
1 – 21
926.4 – 927.6,
902.4 – 910.4
For nodes operating in the 868 MHz range, the radio uses the same three frequencies (868.1 MHz,
868.3 MHz, and 868.5 MHz) for all communications, regardless of the channel specified. Radios on
different channels cannot communicate with each other, but can interfere with each other.
This function takes no parameters.
getEnergy() – Get energy reading from current channel
The getEnergy() function returns the result of a brief radio Energy Detection scan on the currently
selected channel. The result is in the same units as the getLq() function.
Using getEnergy() on radios working with frequency-hopping firmware is more cumbersome. This
includes 900 MHz radios running FHSS firmware and 868 MHz radios.
Because each SNAP channel in sub-GHz firmware comprises a number of discrete frequencies, you
must explicitly query the energy level at each frequency in use for your SNAP channel. For 900 MHz
radios, this means you must step through each of the 25 900 MHz-band “channels” in your range,
making a separate getEnergy() call for each. (See the explanation of 900 MHz FHSS frequency
hopping in the getChannel() function description for more details.) For 868 MHz radios, you must
check each of the three 868 MHz-band frequencies in use (channel 0, channel 1, and channel 2) and
average the three values. (Regardless of which SNAP channel is specified, 868 MHz radios always use
the same three frequencies for their communications.)
For purposes of getEnergy(), then, the range of valid values for the setChannel() function extends from
1 to 64, rather than the normal range you would use for setting a broadcast or receive channel. You
should not use channel numbers outside the normal range of 0 to 15 except when attempting an energy
scan. After performing an energy reading, be sure to set the channel back to the appropriate SNAP
network channel to be able to communicate with your other nodes.
SNAP Reference Manual Document Number 600-0007K Page 49 of 202