Documentation Omission: IDD polarity on Nucleo-64 Boards (UM1724)

Andrew Neil · ‎2025-06-09

There's nothing in the manual which tells you which pin is source, and which is load!

PS:

Even the schematic doesn't help!

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

mƎALLEm · ‎2025-06-09

Hello,

I don't think this is something critical or blocker as connecting the ammeter in different polarity gives the same power consumption value but with different sign.

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Andrew Neil · ‎2025-06-09

Indeed, if you're just using a digital ammeter or DMM, the sign will tell you if you have it the right way around.

But a DMM really isn't a very useful tool - it can't show rapid variations.

It can't even show you the 100ms on/off of the LED in the standard demo code.

For that, you need some sort of proper power analyser - and then you do need to know which way around to connect it!

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Peter BENSCH · ‎2025-06-09

Well, if you want to operate the target without STS-LINK/V2-1 and only want to feed in there, this may play a role. However, according to schematics, the left pin of JP6 here is VDD, which can also be found on CN7.5.

However, the GERBER also shows the connections, e.g. as in the following picture, in which I have marked the tracks in colour:

+3V3 = red
VDD = dark green

But @Andrew Neil surely means that this could also be in the UM1724.

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Andrew Neil · ‎2025-06-09

I couldn't find the PCB layout as a PDF on the CAD Resources page - just Gerbers & Schematics

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Andrew Neil · ‎2025-06-09

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

mƎALLEm · ‎2025-06-09

@Andrew Neil wrote:

From my standpoint this is something that could be indicated by silkscreen on the PCB.

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Andrew Neil · ‎2025-06-09

Absolutely: I think it should be indicated - either on the silkscreen, or by the usual indication of "Pin 1" of the header by a square pad.

(as seen for JP5 in the image posted by @Peter BENSCH)

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Peter BENSCH · ‎2025-06-09

I don't really understand the problem - any PDF viewer can do PDF, but it is static, you only see the default view. GERBER can be used by any GERBER viewer, which is also available free of charge, e.g. as part of KiCAD, where, unlike PDF, you can select the layers to be displayed and their colours?

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Andrew Neil · ‎2025-06-09

It's just inconsistent: mostly ST provide PDF - so there's no need to have a Gerber viewer.

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.