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Joined: 31/12/2012
Location: New ZealandPosts: 9992
| Posted: 03:05am 18 Jun 2021 |
Radiometrix NTX2/NRX2 pair, narrowband 434.650MHz @ 25mW 10kbps.
I have a project using these modules, and they are working fine, but some of the ones at the far edge of the range don't always respond as well as I would like. They retry till reset, so it's not a major, but it does 'Annoy' me.
I used 15 "U" character bytes to sync the data-slicer in the receiver, and that works very well for all the units closer to the receiver, but the ones on the outer edge - not so much. Data baud-rate is 2400, so WELL within the 10kbps rating of the modules.
I thought I would try adding more pre-amble, so I increased it from 15 bytes to 50 bytes of "U", thinking and hoping this would give the receiver more time to sync, but this does not really appear to be the case.
So, the question is: Can you have TOO MUCH pre-amble?
I have noted that a couple of units I updated the firmware in that are well within range, now don't always work with 50 sync bytes, and I have had to go back to 15 - which then works.
That is odd to me - I figured more would be better when it comes to sync bytes.
One of my other tech chums here also suggested I should be having POST-amble bytes also, but I fail to see the need for that, so what do the members think of the post-amble idea? I was of the opinion, that once you sync the receiver, there should not be any need for post-amble bytes, as you only need the sync so the receiver starts counting bytes at the right place. Once it has the last byte, the system does not care if the rest of the RX output is white-noise - it will simply ignore it till the next sync burst.
Thoughts and comments?
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