I am new here, and new to designing PCBs and electronics in general. So I might have miss the obvious answers to my questions while searching before I made this post. I may also be using the wrong terminology, feel free to correct me! I hope this is a suitable place on the forum to discuss and maybe find an answer my questions.
Some background:
I use both KiCad 6 (6.0.10) and KiCad 7 (7.0.1) and was going to follow along one in a tutorial made by Phil’s Lab. The video itself uses KiCad 6, but I am pretty sure the video will be perfectly fine to follow in KiCad 7 if I didn’t have this particular issue.
Phil uses the STM32F103C8Tx symbol in this video. In KiCad 7 two pins are missing from the same symbol, I’ve attached an image with each version for easy reference. In the KiCad 7 version I already changed the x to 6 as Phil do in his video but it should be an x if it was left unchanged.
The first picture is KiCad 6, the second KiCad 7. I assume this is an error and that the symbol for KiCad 6 is how the symbol should look. Especially since the missing pins are 47 and 35 and those exist in the datasheet.
So my main questions are these:
If I want to add those two pins to the KiCad 7 version is it safe to do so?
Could it mess something else up if I edit the pre-existing symbol, or would it be better to create new symbols and maybe even footprints using KiCad 6 as reference?
Yea this stacking of the pins is something new, and ounce again KiCAD seems to be deviating from eCAD norms, at least in my experience with other programs.
I also dislike pin stacking for power pins on chips. I want to know what every pin is connected to, especially when probing (as checking power pins is the first step) – if the power pins are hidden on the schematic that is totally unacceptable. I do not even want no-connect pins on a chip to be stacked. A person unfamiliar with the design that is tasked with board test also needs to be able to completely understand where every pin goes.
However, pin stacking has some good uses. Multiple pin connections to shield cans on connectors and such can be piled together as one shield pin, to de-clutter the schematic symbol. And something like this 4-pin pushbutton looks much cleaner as a 2-pin symbol, though I don’t actually stack the hidden pins, but rotate them 90 degrees so it is obvious when editing the symbol:
This is yet another reason to make your own library and tweak everything to your liking. The kicad-provided libraries are very comprehensive and useful, and a great way for folks to start using the software right away. But if you want to change some things, start making symbols and footprints – it’s really quite easy to do
It gets worse.
This symbol, opened in the symbol manager, shows three pins under the pin 23 VSS. There is an extra pin numbered 49 and also labeled VSS as well as pins 35 & 47.
This gives a total of 49 pins on a 48 pin package.
I don’t have v7 libraries installed, so I can’t check the assigned footprints.
But the STM32F103C8Tx is available as 48 LQFP and as 49pin UQFP with central bottom solder pad. So the symbol-definition seems not totally false, it’s only ambiguous.
Admittedly it would be better if the type of footprint (the “x” in the symbol-name) would be reflected in the symbol.
Additional personal remark: I like the stacked power-pins very much, they greatly reduce the schematic-cluttering.
I also like the pin stacking but also see the problem with lost information. maybe it would be an option to not hide the pin number of the stacked pin but instead show it on the visible pin as well?
I originally thought pin 49 would be a power pad, but I couldn’t find that package. After some confusion the ST32F103C8Tx is available as LQFP and identified as STM32F103CBTx with the drawing STM32F103C6Ux and the UQFP is STM32F103CBUx with its own drawing STM32F103CBUx.
Pin stacking makes some interpretations so difficult. I’m a member of the dislike camp.
Me too.
If I have a project, then I want to be able to find each and every pin in the schematic. When I’m fault-finding on a PCB, and I can’t find some pins in the schematic, then that is just another extra complication. My solution is to load the symbol in the editor and just unstack the pins to make them visible again.
