Bug #3269
closed
osmo-e1-xcvr has magnetics not placed the right way
Added by tnt almost 6 years ago.
Updated almost 6 years ago.
Description
It seems the footprint for the T1094NL transformer in the library is wrong.
The pads in the schematics are correct but their position on the footprint is wrong. P$16 is where P$1 should be, P$15 is where P$2 should be and so on and so forth.
Also pads have the default P$nn which is probably a clue as to what happened :p
The result is that there is no orientation of the transformer that will give the right result because one side is 1:1 and the other is 1:2.
Currently for the RX path, this has no effect. Primary and secondary are swapped but it's a 1:1 turn ratio.
For TX however, the '2' turn ratio should be on the line side and instead it's on the LIU side, so the pulses will end up being 1/4 amplitude of what they should be.
I'm sorry for the fuckup :( I guess we could do some new boards and re-cycle the magnetics and LIU, as those are the expensive parts.
I don't think that's necessary.
(1) it might just work since the pulse are just attenuated by 1/4 and for short distance it's fine
(2) You can rework to connect one of the pin on the LIU side to the center tap instead, this would bring in a 1:1 ratio. Not the expected 1:2 but it means the pulses are only 1/2 instead of 1/4 which is already much better.
Since the board is only for experimentation I think the existing one will be good enough for that purpose. Of course still worth fixing the footprint for future use :p
- Assignee changed from laforge to mschramm
- Status changed from New to In Progress
- Status changed from In Progress to Resolved
commit 00ebf25701b56d68a74c90c9afd7e1c6ff67fd61
Author: Martin Schramm <mschramm@sysmocom.de>
Date: Tue May 29 19:52:28 2018 +0200
replace old PULSE_T1094NL footprint, repair pin assignment (solves OSM#3269)
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