AN633
Rev. 0.7
71
Figure 52. Observation of the Automatic RX Hopping
There are three configurable hop conditions that can be used to determine whether to continue hopping or to stay
on a particular channel. These conditions are as follows:
RSSI timeout
: After the receiver chain is settled, a timer is started and the RSSI is averaged within this time
(if the average is enabled). If the RSSI is above the desired threshold, then the radio stays on the actual
channel. If timeout occurs without the RSSI exceeding the threshold, the radio will automatically hop to the
next channel. The RSSI timeout can be set in bit units.
Preamble timeout
(invalid preamble pattern): Invalid preamble timeout starts once the receiver chain is
settled. If it timeouts without detecting the preamble (the preamble detection condition is determined by the
preamble detection threshold), then the radio automatically hops to the next channel. The invalid preamble
timeout is configurable.
Note:
1. The invalid preamble timeout must be longer than the preamble detection threshold.
2. If the preamble is detected within the timeout and the radio stays on the actual channel, then the sync word conditions
determine the further radio behavior.
Sync word invalid timeout
(invalid or no sync word detected after the preamble): After the preamble is
detected, the radio is looking for the sync word. Once non-preamble bits are received, the radio starts a
timer. If the sync word is received within sync word 4 bits time, then the radio starts to fill the
payload into the RX_FIFO. If the timer timeouts without detecting the sync word, then the radio will hop to
the next channel automatically. The sync timeout is not configurable, and it cannot be disabled.
Some considerations:
The RSSI detection is the fastest way to detect if a channel is occupied or not. However this method does not qualify if
the received signal is sent with the expected radio parameters; therefore, even an un-modulated disturber signal can
influence the RSSI measurement and result in a false detection. Please also note that the read RSSI value is radio con-
figuration dependent; therefore, it is recommended that one measure the input power vs. RSSI curve for each radio set-
tings respectively. The RSSI curve gets more accurate a few dB above the sensitivity level; therefore, it is highly
recommended that one use at least a 4 bits time average and set the RSSI threshold to 3dB above the sensitivity level.
The preamble detection method is more reliable than the RSSI method, because it requires demodulating the incoming
signal and it acts only on the data stream that is sent with the desired radio parameters. Occurrence of a short preamble
pattern is frequently from the white noise that is generated by the demodulator if nothing is transmitted. Therefore, if the
preamble detection threshold is set relatively short, then a false preamble detection may occur and prevent the channel
hop as long as a next condition does not trigger a hop. This time period may prevent the reception of a valid packet that
is transmitted during the same time. To avoid such situations, a longer (1.5 … 2 bytes) detection threshold is suggested.
Summary of Contents for EZRADIOPRO Si4060
Page 24: ...AN633 24 Rev 0 7 Figure 20 Supply Current versus Time Diagram from Shutdown to RX State...
Page 67: ...AN633 Rev 0 7 67 Figure 48 Variable Length Packet Reception Flowchart...
Page 69: ...AN633 Rev 0 7 69 Figure 50 Packet Matching Reception Flowchart...
Page 73: ...AN633 Rev 0 7 73 Figure 54 Packet Reception with Automatic RX Hopping Flowchart...
Page 75: ...AN633 Rev 0 7 75 Figure 56 Packet Reception with Manual Rx Hopping...
Page 80: ...AN633 80 Rev 0 7 Figure 62 Long Packet Transmission Workflow...
Page 81: ...AN633 Rev 0 7 81 Figure 63 Long Packet RX Flowchart...
