Pin Direction

Yes, the descriptions for pin directions are confusing, particularly for

SUPPLY and POWER.  These words mean pretty much the same thing and the

description doesn't help distinguish the difference very well.

Basically, use SUPPLY only for symbols meant to indicate a supply net in a

schematic, like for a ground symbol.  Use POWER for power and ground pins

of a IC.  The 7805 should have the ground and power pins set to POWER.

The general idea of distinguishing between these pin types is good, but

there are two serious problems with this in Eagle.  First, POWER pins are

automatically connected to a net matching the pin name if such a net

exists.  That is a really bad idea.  I suppose someone thought they were

saving us a little work, but I really really don't like the software making

connections I didn't explicitly define.  To do it without even a warning or

hint takes it from bad to downright irresponsible.

The second problem is when you run the ERC it will complain about POWER

pins connected to nets of different names than the pin name.  This is quite

annoying since these warnings can make it hard to notice a legitimate

problem in the list.  This has also been brought up here for a long time

but Cadsoft has so far refused to budge.  Maybe this will finally be fixed

in version 6.

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

On 11/3/2011 2:59 PM, Olin Lathrop wrote:

Yes, the descriptions for pin directions are confusing, particularly for

SUPPLY and POWER.  These words mean pretty much the same thing and the

description doesn't help distinguish the difference very well.

 

Basically, use SUPPLY only for symbols meant to indicate a supply net in a

schematic, like for a ground symbol.  Use POWER for power and ground pins

of a IC.  The 7805 should have the ground and power pins set to POWER.

 

The general idea of distinguishing between these pin types is good, but

there are two serious problems with this in Eagle.  First, POWER pins are

automatically connected to a net matching the pin name if such a net

exists.  That is a really bad idea.  I suppose someone thought they were

saving us a little work, but I really really don't like the software making

connections I didn't explicitly define.  To do it without even a warning or

hint takes it from bad to downright irresponsible.

 

The second problem is when you run the ERC it will complain about POWER

pins connected to nets of different names than the pin name.  This is quite

annoying since these warnings can make it hard to notice a legitimate

problem in the list.  This has also been brought up here for a long time

but Cadsoft has so far refused to budge.  Maybe this will finally be fixed

in version 6.

Thanks for your explanation.  I agree it is a terrible idea to

automatically connect these pins to a net, especially when the "stock"

library components have inconsistencies in how pins are designated.

On 11/3/2011 2:59 PM, Olin Lathrop wrote:

Yes, the descriptions for pin directions are confusing, particularly for

SUPPLY and POWER.  These words mean pretty much the same thing and the

description doesn't help distinguish the difference very well.

 

Basically, use SUPPLY only for symbols meant to indicate a supply net in a

schematic, like for a ground symbol.  Use POWER for power and ground pins

of a IC.  The 7805 should have the ground and power pins set to POWER.

 

The general idea of distinguishing between these pin types is good, but

there are two serious problems with this in Eagle.  First, POWER pins are

automatically connected to a net matching the pin name if such a net

exists.  That is a really bad idea.  I suppose someone thought they were

saving us a little work, but I really really don't like the software making

connections I didn't explicitly define.  To do it without even a warning or

hint takes it from bad to downright irresponsible.

 

The second problem is when you run the ERC it will complain about POWER

pins connected to nets of different names than the pin name.  This is quite

annoying since these warnings can make it hard to notice a legitimate

problem in the list.  This has also been brought up here for a long time

but Cadsoft has so far refused to budge.  Maybe this will finally be fixed

in version 6.

Thanks for your explanation.  I agree it is a terrible idea to

automatically connect these pins to a net, especially when the "stock"

library components have inconsistencies in how pins are designated.

John Friede schrieb:

Thanks for your explanation.  I agree it is a terrible idea to

automatically connect these pins to a net, especially when the "stock"

library components have inconsistencies in how pins are designated.

I think that the libraries have grown over the years, with different

and/or changing authors...

By looking at them, you learn that the only libraries you can really

trust are those you created by yourself.

Tilmann