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Pcbnew: Disallow invalid mwwave inductor lengths 

Some microwave inductor lengths cause invalid outputs
for the calculations, which causes jagged outputs.

* If the request length is such that four arcs and no straight
  segments is too long
* If the length is such that an N-turn coil is too short, but
  an N+1-turn coil is too long. This can happen when the coil
  count is small.

This patch doesn't fix the underlying geometric issue here - fixing
the first requires a numerical method, and fixing the second probably
needs an iterative approach. Both of these could benefit from
a refactor.

However, this patch does prevent the tools producing invalid outputs,
which can sometimes be quite subtle mistakes if the "jags" are small.

Fixes: lp:1792119
* https://bugs.launchpad.net/kicad/+bug/1792119
This commit is contained in:
John Beard 2019-01-24 17:02:12 +00:00 committed by Seth Hillbrand
parent 8b060799eb
commit d39cdb5565
1 changed files with 49 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
pcbnew/microwave/microwave_inductor.cpp
View File

@ -79,6 +79,15 @@ static void gen_arc( std::vector <wxPoint>& aBuffer,
}
enum class INDUCTOR_S_SHAPE_RESULT
{
OK, /// S-shape constructed
TOO_LONG, /// Requested length too long
TOO_SHORT, /// Requested length too short
NO_REPR, /// Requested length can't be represented
};
/**
* Function BuildCornersList_S_Shape
* Create a path like a S-shaped coil
@ -88,10 +97,8 @@ static void gen_arc( std::vector <wxPoint>& aBuffer,
* @param aLength = full length of the path
* @param aWidth = segment width
*/
static int BuildCornersList_S_Shape( std::vector <wxPoint>& aBuffer,
const wxPoint& aStartPoint,
const wxPoint& aEndPoint,
int aLength, int aWidth )
static INDUCTOR_S_SHAPE_RESULT BuildCornersList_S_Shape( std::vector<wxPoint>& aBuffer,
const wxPoint& aStartPoint, const wxPoint& aEndPoint, int aLength, int aWidth )
{
/* We must determine:
* segm_count = number of segments perpendicular to the direction
@ -171,7 +178,7 @@ static int BuildCornersList_S_Shape( std::vector <wxPoint>& aBuffer,
if( radius < aWidth ) // Radius too small.
{
// Unable to create line: Requested length value is too large for room
return 0;
return INDUCTOR_S_SHAPE_RESULT::TOO_LONG;
}
}
@ -192,6 +199,30 @@ static int BuildCornersList_S_Shape( std::vector <wxPoint>& aBuffer,
// reduce len of the segm_count segments + 2 half size segments (= 1 full size segment)
segm_len -= delta_size / (segm_count + 1);
// at this point, it could still be that the requested length is too
// short (because 4 quarter-circles are too long)
// to fix this is a relatively complex numerical problem which probably
// needs a refactor in this area. For now, just reject these cases:
{
const int min_total_length = 2 * stubs_len + 2 * M_PI * ADJUST_SIZE * radius;
if( min_total_length > aLength )
{
// we can't express this inductor with 90-deg arcs of this radius
return INDUCTOR_S_SHAPE_RESULT::TOO_SHORT;
}
}
if( segm_len - 2 * radius < 0 )
{
// we can't represent this exact requested length with this number
// of segments (using the current algorithm). This stems from when
// you add a segment, you also add another half-circle, so there's a
// little bit of "dead" space.
// It's a bit ugly to just reject the input, as it might be possible
// to tweak the radius, but, again, that probably needs a refactor.
return INDUCTOR_S_SHAPE_RESULT::NO_REPR;
}
// Generate first line (the first stub) and first arc (90 deg arc)
pt = aStartPoint;
aBuffer.push_back( pt );
@ -257,7 +288,7 @@ static int BuildCornersList_S_Shape( std::vector <wxPoint>& aBuffer,
// push last point (end point)
aBuffer.push_back( aEndPoint );
return 1;
return INDUCTOR_S_SHAPE_RESULT::OK;
}
@ -298,7 +329,6 @@ MODULE* MWAVE::CreateMicrowaveInductor( INDUCTOR_PATTERN& inductorPattern,
*/
D_PAD* pad;
int ll;
wxString msg;
auto pt = inductorPattern.m_End - inductorPattern.m_Start;
@ -324,14 +354,22 @@ MODULE* MWAVE::CreateMicrowaveInductor( INDUCTOR_PATTERN& inductorPattern,
// Calculate the elements.
std::vector <wxPoint> buffer;
ll = BuildCornersList_S_Shape( buffer, inductorPattern.m_Start,
inductorPattern.m_End, inductorPattern.m_length,
inductorPattern.m_Width );
const INDUCTOR_S_SHAPE_RESULT res = BuildCornersList_S_Shape( buffer, inductorPattern.m_Start,
inductorPattern.m_End, inductorPattern.m_length, inductorPattern.m_Width );
if( !ll )
switch( res )
{
case INDUCTOR_S_SHAPE_RESULT::TOO_LONG:
aErrorMessage = _( "Requested length too large" );
return nullptr;
case INDUCTOR_S_SHAPE_RESULT::TOO_SHORT:
aErrorMessage = _( "Requested length too small" );
return nullptr;
case INDUCTOR_S_SHAPE_RESULT::NO_REPR:
aErrorMessage = _( "Requested length can't be represented" );
return nullptr;
case INDUCTOR_S_SHAPE_RESULT::OK:
break;
}
// Generate footprint. the value is also used as footprint name.