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I have a schematic that is throwing a spurious warning. The schematic
is hierarchical, with multiple instances of a LED driver IC with
associated LEDs. To allow each of the LED drivers to be identified on
the I2C bus, I have exported the three address-setting pins and the 5V
rail (each driver is on its own filtered 5V supply). Each
address-setting pin can be connected to ground, 5V, or left floating,
all three having a significance to setting the I2C address.

The eeschema ERC has no problems with the address lines being marked
with a no-connection flag, but it chokes on the 5V output being so
marked, giving a warning, 'A pin with a "no connection" flag is
connected'. If I remove the no-connection flag from the 5V output, I
then get an error, 'Pin not connected'.

I could just ignore the warning, but since I don't understand what is
the problem, I thought I would first ask if anyone knows.

Hopefully the screen-shot I've attached is visible to you and clarifies
what I'm describing.

Regards,

Robert.

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The V5DRV is basically a power out pin
That would connect to a power net somewhere. I'll guess to the LED string
or power LED

You can either connect it with a line or put some form of power flag on
it, with the LEDs connected to the same net but be careful as you have
multiple copies of the driver on the cct that you make each one a
different net or erc will really complain.

Andy



On Thu, 3 Oct 2024 12:26:00 +0100
"Robert via groups.io" <birmingham_spider@...> wrote:

I have a schematic that is throwing a spurious warning. The schematic
is hierarchical, with multiple instances of a LED driver IC with
associated LEDs. To allow each of the LED drivers to be identified on
the I2C bus, I have exported the three address-setting pins and the 5V
rail (each driver is on its own filtered 5V supply). Each
address-setting pin can be connected to ground, 5V, or left floating,
all three having a significance to setting the I2C address.

The eeschema ERC has no problems with the address lines being marked
with a no-connection flag, but it chokes on the 5V output being so
marked, giving a warning, 'A pin with a "no connection" flag is
connected'. If I remove the no-connection flag from the 5V output, I
then get an error, 'Pin not connected'.

I could just ignore the warning, but since I don't understand what is
the problem, I thought I would first ask if anyone knows.

Hopefully the screen-shot I've attached is visible to you and clarifies
what I'm describing.

Regards,

Robert.

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I tried putting a disconnected line on V5DRV, and also a line to a
no-connect flag, but neither was acceptable to the ERC.

I've also tried changing the pin type (input, passive etc), and
connecting it to different random places in the hierarchical sheet.

In the hierarchical sheet V5DRV is connected to VDD on the driver IC
(the LEDs have their own supply, the driver acting as a current sink),
and therefore there's a power flag within the sheet to keep the ERC
happy. I've attached a screen-shot of the relevant part of the
hierarchical sheet.

Regards,

Robert.

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On 03/10/2024 14:15, Andy via groups.io wrote:

The V5DRV is basically a power out pin
That would connect to a power net somewhere. I'll guess to the LED string
or power LED

You can either connect it with a line or put some form of power flag on
it, with the LEDs connected to the same net but be careful as you have
multiple copies of the driver on the cct that you make each one a
different net or erc will really complain.

Andy

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Close, Kerim, but no cigar!

I've been experimenting further, and it seems that if a sheet pin is
connected to more than one pin in the sub-sheet (in this case there are
three paralleled capacitors and VDD on the IC), the ERC reports the
error. So the logic must be that a no-connect flag can only be
connected to one pin, but a sheet pin can in effect be multiple pins (so
Kerim was on the right track). The fact that the sheet pin is an
output is not taken into consideration.

So as a work-around I've moved the power flag from the sub-sheet to the
sheet above, with one power flag for each instance of the sub-sheet. I
can then always connect the V5DRV sheet pin to something, even if it's
just a power flag. I've attached an image that hopefully makes that clear.

Regards,

Robert

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On 04/10/2024 05:20, Kerim via groups.io wrote:

For instance, it happened to me once that I duplicated a pin at the same place by mistake. Apparently, nothing looked wrong. But this gave me a continuous warning no matter what I did... till I discovered my mistake.

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