How can I see the effective electrical length in KiCad for a differential pair?

[Robert2]

I used to see the Effective Electrical Length displayed in the status bar when selecting a trace from a differential pair in KiCad 8.0. However, for some reason, this measurement no longer appears. Does anyone know how to enable or display the effective electrical length in KiCad?

[JamesJ]

Which version are you on? Seems to be working fine in 8.0.7. Can you share a project with the issue?

[Robert2]

Hi! I am using KiCad version 8.0.6. So in version 8.0.7 you can see the effective electrical length(not routed length) in the status bar? I am asking this because I am not sure if I remember correctly. I can’t share the project, because the site says new users are not allowed to share attachments.

[JamesJ]

@Robert2

Effective Electrical Length

Ah I was looking at Routed Length as that’s what the arrow was pointing at… I’m not sure I recall ever seeing effective electrical length - I’d have to go back through the code to see when it was present as a string. What do you expect it to be calculating for ‘effective electrical length’?

[Robert2]

I am new to kiCad and electrical engineering, so I might be wrong. I am using an USB that has a differential pair. I am trying to match the length of each of the traces as good as possible. I remember there were 2 measurements for the length of the traces that make up the differential pair. The routed length that shows the length of the routed traces and another measurement that shows a length that also takes in consideration the differences in propagation speed due to variations in impedance, dielectric constant of the substrate, and trace geometry. Do you know something like this?

[eelik]

@Robert2

I am new to kiCad and electrical engineering

Routing differential pairs on USB C connector

I’m trying to route the D+ and D- differential pair on KiCad for a USB C connector and can’t seem to find the answer. I am able to route the two middle D+ and D- pair in the center of the connector but connecting the outer D+ and D- on the connector seems to be an issue. Attached is my current schematic. I’m assuming that the outer connectors need to be tuned for length as well. Any tips here? [route]

See also the Toradex recommendation from Length matching SDIO interface - #3 by eelik. You should know what speed you are using, and for USB2 max. speed 1mm difference isn’t yet too much. In case of 12Mb/s almost anything goes. USB3 is a different matter.

[JamesJ]

@Robert2

The routed length that shows the length of the routed traces and another measurement that shows a length that also takes in consideration the differences in propagation speed due to variations in impedance, dielectric constant of the substrate, and trace geometry. Do you know something like this?

KiCad can’t calculate this - it has no concept of time-domain length tuning (yet… I want to add it). As @eelik says, unless you’re routing very fast / sensitive signals, then you don’t need to worry about those kind of details when matching trace lengths.

[Robert2]

Thank you for the help!

[jmk]

@Robert2

I can’t share the project, because the site says new users are not allowed to share attachments.

You can share now if you ever wish. You have self promoted to “Basic”.
Read about the forum system here.

[davidsrsb]

KiCad calculator has coupled microstrip lines at the surface, but no calculator for pairs on inner layers, between two planes at maybe different spacings and slightly different Er