Frequencies?

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6 months 1 week ago #271 by achoward
Frequencies? was created by achoward
Mario, John can fill you in on details of how the systems worked today. I remember awhile back you and I talked about the 900MHz of the Eggfinder trackers and from the little test we did then, there didn't seem to be a problem, but that was quite awhile ago. Folks are also using some other brand 900MHz trackers. So, John wanted me to ask you about the freq of the WLCS. Any thoughts if our systems causing a problem?  My Eggfinders are all set to 911, code 2 and my telemetry modules are set to 911, code 5. Not sure what the other trackers are set at.
Allan

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6 months 1 week ago - 6 months 1 week ago #273 by admin
Replied by admin on topic Frequencies?
Allan,

The system is running on an RF95 LoRa radio at 915mHz, the bandwidth is 500 and the spreading factor is 128. All messages are originated by the Launch Controller and include a 16 byte string that is unique to the system (that’s why the devices need to be paired.) There is also a handshaking protocol that goes roughly like this:

LC = Launch Controller
PC = Pad Controller

LC sends a command
All PCs receive the command and parse it.
  If the System ID doesn’t match the PC ignores the message.
  If the Bank doesn’t match the PC ignores the message.
  If the Group doesn’t match the PC ignores the message.
  If the previous item match the PC sends an acknowledgement.
If the LC receives a properly encoded acknowledgement a ‘GO’ message is sent.
  If the PC receives a ‘GO’ message the command is executed.
Otherwise, if the LC did not receive it will retry the message to the retry limit.

So the short answer is the system should ignore messages from other devices even if they are transmitted on the same frequency.

Having said that, it assumes that there is no error in my handling code. I’ve done some testing with spurious signals but it would be best to get a few of these devices together with the system connected to my computer where I can monitor what is being received and how the launch system is responding to it.

Anyone care to bring some of these devices over for a testing session some day?
 
Last edit: 6 months 1 week ago by admin.

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6 months 2 days ago #281 by achoward
Replied by achoward on topic Frequencies?
Yes, I could bring over some Egg stuff to check.

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5 months 4 weeks ago #284 by admin
Replied by admin on topic Frequencies?
Great! We’re up to our ears in home remodeling at the moment but we should be able to get together for testing soon. 
thanks!

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