Here are frequently asked question about LoRa sampling, samples after a device reboot, transmission, and threshold alerts.
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LoRa Transmission and Threshold Alerts
Sampling Information
How does LoRa know which sample to send? For example, if you have four channels that sample once every half-hour, which channel's sample does it send every fifteen minutes?
A special queue in the device is designated for LoRa data samples. The queue size is 1.
When a channel (not a group) samples, it tries to enter a sample to the queue, but, if there is already one sample of that channel in the queue, it will overwrite it in the same place in the queue. It will remove the older sample and put the newer sample in its place, but the sample will remain in the same place in the queue. Consequently, only one sample of every channel is in the queue at every single point in time, and it's the newest sample of that channel.
The queue cannot contain more than one sample (from analog, serial, and digital streams) from every channel at any point in time, and the one sample of each channel is the newest sample of that channel.
If there are no samples of that channel in the queue, it will enqueue the sample in FIFO order, but only if there is a free cell in the queue.
If there is no place in the queue, then:
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In a LoRa-only device, the samples are discarded.
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In a LoRa-enhanced device, all samples are stored on the SD card and transmitted by cellular at the next transmission. For example, if we have two channels, one sample of each can be in the queue. If we have 16 channels, only a subset of them can be in the queue.
The channels will transmit in something like a round robin order, as long as the number of channels is equal or less than the queue size.
If transmission is by LoRa every five minutes, will the device stop transmitting after a while because all permitted LoRa transmissions are used up?
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In EU - yes, it will stop transmitting after a while and for some time, until the next day, more or less.
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In US - no, because the limitations there are much less strict.
Note that it will stop transmitting LoRa samples, but data sampling continues.
Health Counter Information
What health counter data is sent by LoRa?
No health counter data except Internal Battery Life% and External Power Voltage (if external power is used) is sent. Internal Battery Life% is sent every 12 hours.
Samples After a Device Reboot
What happens to the sample data when the device is rebooted?
In a LoRa-only device, all LoRa samples are in RAM only. So, if the Wavelet is rebooted for any reason, they are deleted.
In a LoRa-enhanced Wavelet, samples are also stored on the SD card and will be transmitted via cellular as well.
Comparison of LoRa-only and LoRa-enhanced Devices
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LoRa-only Device |
LoRa-enhanced Device |
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What communication is used? |
LoRa only |
LoRa + cellular network |
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What is the queue size? |
1 |
1 |
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Which samples are transmitted? |
Serial, Analog, Digital From Health counters – only:
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Serial, Analog, Digital
All Health counter data |
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Where are samples stored? |
RAM only |
RAM and SD card |
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If there is no free space in a queue, what happens? |
Samples are discarded |
Samples transmitted at the next cellular transmission |
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If the Wavelet is rebooted, what happens? |
All samples in RAM are discarded |
Samples stored in SD are sent with the next transmission |
LoRa Transmission and Threshold Alerts
If you set an alert (threshold), will it be sent by GSM or by LoRa?
From the LoRa perspective, alerts are normal samples and there is nothing special about the threshold. The order of LoRa-transmitted samples is described in Sampling Information.
If you have a LoRa-enhanced device (GSM cellular network is enabled) and the threshold is reached to initiate a transmission, then the event sample will be transmitted over cellular network immediately.
If you have a LoRa-only (no GSM) device and a threshold is reached to initiate a transmission, nothing happens.