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#97 Netlists are missing connections
Net "aliases" are made by putting a net label on a net which already has a "label" or "power label" connected to it. This should just give the net two names, and when generating a netlist, it should appear as one net.
When net aliases are used for power nets (and probably when used for any nets), netlists are not generated correctly. There are missing connections and/or isolated nets. The attached schematic should produce a netlist which connects the 3V3 net to U1.3, C1.1 and C2.1. However, C1.1 is missing completely from the netlist. The only net that shows up is the "PWR2" net, which connects U1.3 and C2.1.
I recently encountered this problem with a large multi-page schematic I generated in TinyCAD. The broken netlist created a lot of headaches for the layout engineer, because the netlist was missing connections on almost all of the power pins and nets which had multiple labels. It also had isolated nets where they should have been tied to a power net. The netlist problem is the only bug I encountered that makes TinyCAD unusable for a production environment.
Schematic which produces incorrect netlist
There are a few issues with power symbols and named nets - also with multiple net labels attached to the same net.
In this example case on the 'power' page there are effectively three net names on the same net.
I suspect in this case the parsing process has processed page 'power' net from 3.3V to PWR1 then to PWR2 attached to U1p3. (Only one name allowed per net)
Then when page 'Capacitors' is processed only PWR2 is matched to a now existing net.
PWR1 is therefore a single pin net and not listed.
If PWR1 had more pins on the same page it would have been listed but possibly without the effective connection to PWR2.
I do not use the power symbols (probably from previous experience) but only use net labels. I have also learned not to put more than one lable on a net as this can also cause problems. It seems that power symbols have inherent labels which also feed the issue.
I think this was raised some time ago in various guises before v2.70.01.
Hope that helps
Phil
Series8217 - Did you encounter this problem on TinyCAD 2.60.01, or on one of the beta's for 2.70.00? We addressed this bug in the beta version, but it is possible that there is an aspect of it that we didn't catch. Please let me know which version of TinyCAD you experienced this on. If 2.60.01, please try out the latest beta for 2.70.00 and see if this doesn't fix the problem.
Thanks,
Don Lucas
Phil and Don, thanks for the replies.
Don, I am encountering this problem in version 2.70.00 Build #248 Beta.
It sounds like Phil has described the cause of the problem.
On a related note, what is the reason that power symbols are treated differently from normal net labels?
Shall it be possible to generate a net list with multiple net names? Won't this confuse the PCB designer more than it helps the schematics design?
In my opinion multiple net names should not pass the DRC. Any thoughts about this Phil?
If multiple net alises for one net are a problem for the PCB designer or the netlist file format, the schematic designer could be given a dropdown list of aliases for each net, from which they choose the name of the net that should appear in the netlist.
Sorry to have delayed replying.
I think that multiple names on a net should be treated as an error.
Once corrected on the schematic there is no possibility of confusion or mis-reading.
The resulting schematic, netlist and PCB will be consistent.
Phil
The change you are suggesting could be viewed as a regression, since it causes existing schematics with multiple netlist aliases to become broken. Though I don't know if it's an intended feature, TinyCAD does currently support netlist aliases.. besides the bug I encountered, it is otherwise consistent with the behavior of other schematic software I have used, such as Protel.
While multiple netlist names could be discouraged, I don't think they should be removed unless TinyCAD's hierarchical design features improve to the point that large multi-file designs are easier to work with (this will be the topic of another bug). A warning or a DRC fail on multiple names per net would be acceptable (I think Protel supports this), but if the user decides to go through with generating the netlist, I think TinyCAD should just pick one name from the net (or let the user decide).
I'll try working on a patch for this once I can get TinyCAD to compile on my system (I'm trying to get it to work with VSE) .
I have tried having several net labels on wires and the result has been chaos.
Usually because some pins have been omitted.
I don't see why this is a regression and I am not aware of TinyCAD supporting alias net names. Yes you can attach two labels but the netlist will only contain one of them. (Which one is uncertain.)
If you have spread them about the schematic on multiple sheets in this form the problem becomes worse as some or all the names may then appear in the netlist but not correctly connected.
Other software I have used warns about the conflict and may give the opportunity to choose or rename/delete the conflict. Whatever approach is taken, only one name can go through ultimately.
If you force the issue then you are likely to end up with split nets, unconnected pins and a very confused layout chap.
If I'm wrong I would love to see a schematic which uses it successfully.
I can't see it as a bug - just the software trying to make the best of it.
I'd like at least a warning.
Phil
I am presently working on this bug and hope to get it fixed soon.
While you are touching this part of the code, a warning in the DRC for having different labels (or power names) on the same net would be very appreciated.
This problem has now been entirely fixed (but not yet in the repository - I need to do some cleanup before I commit the changes). Your example design file was instrumental in resolving this serious problem. Thanks very much for your help!
The solution will be in the repository in the few days and a new release will be made next week (2.70.04) that includes this fix.
Best regards,
Don
That's fantastic; thanks Don! It looks like this fix is incorporated in 2.80.00. I verified that TinyCAD 2.80.00#396 creates the correct netlist from the example schematic (NetListProblemTest.dsn).
I still need to check if I can get a functional netlist out of my production schematic, which is fairly large and will take me some time to confirm.
Thanks again.
Steven
This problem is fixed in 2.80.00.