kicad-developers team mailing list archive

[Tomasz Wlostowski <tomasz.wlostowski@xxxxxxx>]

On 13.02.2017 18:04, Tomasz Wlostowski wrote:
> On 13.02.2017 17:26, Jon Evans wrote:
>> I verified using Novak's test case on the Launchpad bug report.  DRC
>> error is generated if the distance between the tracks is exactly equal
>> to the clearance. 
>> If you increase the spacing by the minimum distance recognized by the
>> software's precision, the DRC passes.
>> So, I think it's an issue of DRC specification -- The code currently
>> requires that the clearance be *larger* than the minimum in the design
>> rules.
>> The diff pair router is setting the spacing to the minimum (exactly)
>> which causes this bug.
>>
>> IMHO, the DRC code should be changed to "larger or equal to", but I am
>> not sure if there is some subtle reason why it is implemented this way.
>> If you tell KiCad that you can go down to 2mm clearance, you should be
>> able to design something with *exactly* 2mm clearance :-)
> 
> Hi guys,
> 
> The issue is a bit more complex: it's a mix of DRC's floating point
> inaccuracies as well as ill-defined (rounding-error-wise) fixed point
> calculations in the 'gateway' computation part of the diff pair code.
> I'll fix it when my time permits (certainly before v5.0).
> 

Hi again,

I've fixed the rounding issues in the P&S code (patch attached), now the
diff pair gap should always equal the specified value. The DRC checker
still produces some errors, though. I've identified their source is the
DRC::checkMarginToCircle() function. The current clearance test
algorithm is quite complex for me to understand, so I couldn't see any
obvious rounding/comparison issues...

@Jean-Pierre: could you have a look at the attached PCB file and the DRC
errors it produces? A trivial clearance check (see code below) finds no
clearance errors.

Cheers,
Tom

-- snip --

void DRC::testTracks2( wxWindow *aActiveWindow, bool aShowProgressBar )
{
    for( TRACK* segm1 = m_pcb->m_Track; segm1; segm1 = segm1->Next() )
    {
        for( TRACK* segm2 = m_pcb->m_Track; segm2; segm2 = segm2->Next() )
        {
            if ( segm1 == segm2 )
                continue;

            if( segm1->Type() == PCB_VIA_T )
                continue;

            if( segm2->Type() == PCB_VIA_T )
                continue;

            if (segm1->GetNetCode() == segm2->GetNetCode() )
                continue;

            if (segm1->GetLayer() != segm2->GetLayer() )
                continue;

            NETCLASSPTR netclass = segm1->GetNetClass();

            SEG s1 ( VECTOR2I( segm1->GetStart() ), VECTOR2I (
segm1->GetEnd() ) );
            SEG s2 ( VECTOR2I( segm2->GetStart() ), VECTOR2I (
segm2->GetEnd() ) );

            int dist = s1.Distance ( s2 );
            int min_dist  = netclass->GetClearance() +
(segm1->GetWidth() + 1) / 2 + (segm2->GetWidth() + 1 ) / 2;

            if ( dist < min_dist )
            {
                printf("segment/segment clearance failure %p %p dist %d
min_dist %d w1 %d w2 %d cl %d\n",segm1, segm2, dist, min_dist,
segm1->GetWidth(), segm2->GetWidth(), netclass->GetClearance() );
            }
        }
    }
}


(kicad_pcb (version 20170123) (host pcbnew "(2017-02-28 revision fd4e2b0)-master")

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    (area 61.477825 45.17296 219.825668 128.460501)
    (thickness 1.6002)
    (drawings 0)
    (tracks 12)
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  )

  (page A4)
  (title_block
    (date "27 mar 2013")
  )

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    (2 Inner2 signal)
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  )

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  (net 25 TXENABLE)
  (net 26 VAA)
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  (net 28 XCVR_EN)

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    (add_net VAA)
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  )

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>From d8c4f6be00a4cb924c889054871df0d4064b43f3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tomasz=20W=C5=82ostowski?= <tomasz.wlostowski@xxxxxxx>
Date: Wed, 1 Mar 2017 16:37:03 +0100
Subject: [PATCH] Fixed differential pair gap clearance error when gap equaled
 minimum clearance.

---
 pcbnew/router/pns_diff_pair.cpp | 69 ++++++++++++++++++++++++-----------------
 pcbnew/router/pns_kicad_iface.h |  1 -
 2 files changed, 41 insertions(+), 29 deletions(-)

diff --git a/pcbnew/router/pns_diff_pair.cpp b/pcbnew/router/pns_diff_pair.cpp
index 4b2d586..8581464 100644
--- a/pcbnew/router/pns_diff_pair.cpp
+++ b/pcbnew/router/pns_diff_pair.cpp
@@ -406,6 +406,18 @@ void DP_GATEWAYS::FilterByOrientation ( int aAngleMask, DIRECTION_45 aRefOrienta
     } );
 }
 
+static VECTOR2I makeGapVector( VECTOR2I dir, int length )
+{
+    int l = length / 2;
+    VECTOR2I rv;
+    do
+	{
+        rv = dir.Resize( l );
+        l++;
+    } while( ( rv * 2 ).EuclideanNorm() < length );
+
+    return rv;
+}
 
 void DP_GATEWAYS::BuildFromPrimitivePair( DP_PRIMITIVE_PAIR aPair, bool aPreferDiagonal )
 {
@@ -452,8 +464,8 @@ void DP_GATEWAYS::BuildFromPrimitivePair( DP_PRIMITIVE_PAIR aPair, bool aPreferD
         if( w < h )
             std::swap( w, h );
 
-        orthoFanDistance = w * 3/4;
-        diagFanDistance = ( w - h ) / 2;
+        orthoFanDistance = ( w + 1 )* 3 / 2;
+        diagFanDistance = ( w - h );
         break;
     }
 
@@ -462,8 +474,8 @@ void DP_GATEWAYS::BuildFromPrimitivePair( DP_PRIMITIVE_PAIR aPair, bool aPreferD
         int w = static_cast<const SHAPE_SEGMENT*>( shP )->GetWidth();
         SEG s = static_cast<const SHAPE_SEGMENT*>( shP )->GetSeg();
 
-        orthoFanDistance = w + ( s.B - s.A ).EuclideanNorm() / 2;
-        diagFanDistance = ( s.B - s.A ).EuclideanNorm() / 2;
+        orthoFanDistance = w + ( s.B - s.A ).EuclideanNorm();
+        diagFanDistance = ( s.B - s.A ).EuclideanNorm();
         break;
     }
 
@@ -482,18 +494,17 @@ void DP_GATEWAYS::BuildFromPrimitivePair( DP_PRIMITIVE_PAIR aPair, bool aPreferD
 
             if( k == 0 )
             {
-                dir = majorDirection.Resize( orthoFanDistance );
-                int d = ( padDist - m_gap ) / 2;
-
-                dp = dir.Resize( d );
-                dv = ( p0_n - p0_p ).Resize( d );
+                dir = makeGapVector( majorDirection, orthoFanDistance );
+                int d = ( padDist - m_gap );
+                dp = makeGapVector( dir, d );
+                dv = makeGapVector( p0_n - p0_p, d );
             }
             else
             {
-                dir = majorDirection.Resize( diagFanDistance );
-                int d = ( padDist - m_gap ) / 2;
-                dp = dir.Resize( d );
-                dv = ( p0_n - p0_p ).Resize( d );
+                dir = makeGapVector( majorDirection, diagFanDistance );
+                int d = ( padDist - m_gap );
+                dp = makeGapVector( dir, d );
+                dv = makeGapVector( p0_n - p0_p, d );
             }
 
             for( int i = 0; i < 2; i++ )
@@ -531,7 +542,7 @@ void DP_GATEWAYS::BuildForCursor( const VECTOR2I& aCursorPos )
 
             if( !attempt )
             {
-                dir = VECTOR2I( gap, gap ).Resize( gap / 2 );
+                dir = makeGapVector( VECTOR2I( gap, gap ), gap );
 
                 if( i % 2 == 0 )
                     dir.x = -dir.x;
@@ -542,9 +553,9 @@ void DP_GATEWAYS::BuildForCursor( const VECTOR2I& aCursorPos )
             else
             {
                 if( i /2 == 0 )
-                    dir = VECTOR2I( gap / 2 * ( ( i % 2 ) ? -1 : 1 ), 0 );
+                    dir = VECTOR2I( (gap + 1) / 2 * ( ( i % 2 ) ? -1 : 1 ), 0 );
                 else
-                    dir = VECTOR2I( 0, gap / 2 * ( ( i % 2 ) ? -1 : 1) );
+                    dir = VECTOR2I( 0, (gap + 1) / 2 * ( ( i % 2 ) ? -1 : 1) );
             }
 
             if( m_fitVias )
@@ -593,20 +604,22 @@ void DP_GATEWAYS::buildDpContinuation( DP_PRIMITIVE_PAIR aPair, bool aIsDiagonal
 
     VECTOR2I t1, t2;
 
+    auto vL = makeGapVector( dP.Left().ToVector(), ( gap + 1 ) / 2 );
+    auto vR = makeGapVector( dP.Right().ToVector(), ( gap + 1 ) / 2 );
+
     if( sP->Seg().Side( vdP ) == sP->Seg().Side( vdN ) )
     {
-        t1 = aPair.AnchorP() + dP.Left().ToVector().Resize( gap );
-        t2 = aPair.AnchorN() + dP.Right().ToVector().Resize( gap );
+        t1 = aPair.AnchorP() + vL;
+        t2 = aPair.AnchorN() + vR;
     }
     else
     {
-        t1 = aPair.AnchorP() + dP.Right().ToVector().Resize( gap );
-        t2 = aPair.AnchorN() + dP.Left().ToVector().Resize( gap );
+        t1 = aPair.AnchorP() + vR;
+        t2 = aPair.AnchorN() + vL;
     }
 
     DP_GATEWAY gwL( t2, aPair.AnchorN(), !aIsDiagonal );
     SHAPE_LINE_CHAIN ep = dP.BuildInitialTrace( aPair.AnchorP(), t2, !aIsDiagonal );
-
     gwL.SetPriority( 10 );
     gwL.SetEntryLines( ep , SHAPE_LINE_CHAIN() );
 
@@ -646,7 +659,7 @@ void DP_GATEWAYS::BuildGeneric( const VECTOR2I& p0_p, const VECTOR2I& p0_n, bool
 
         if( straightColl || diagColl )
         {
-            VECTOR2I dir = ( p0_n - p0_p ).Resize( m_gap / 2 );
+            VECTOR2I dir = makeGapVector( p0_n - p0_p, m_gap / 2 );
             VECTOR2I m = ( p0_p + p0_n ) / 2;
             int prio = ( padDist > padToGapThreshold * m_gap ? 2 : 1);
 
@@ -654,7 +667,7 @@ void DP_GATEWAYS::BuildGeneric( const VECTOR2I& p0_p, const VECTOR2I& p0_n, bool
             {
                 m_gateways.push_back( DP_GATEWAY( m - dir, m + dir, diagColl, DIRECTION_45::ANG_RIGHT, prio ) );
 
-                dir = ( p0_n - p0_p ).Resize( m_gap );
+                dir = makeGapVector( p0_n - p0_p, 2 * m_gap );
                 m_gateways.push_back( DP_GATEWAY( p0_p - dir, p0_p - dir + dir.Perpendicular(), diagColl ) );
                 m_gateways.push_back( DP_GATEWAY( p0_p - dir, p0_p - dir - dir.Perpendicular(), diagColl ) );
                 m_gateways.push_back( DP_GATEWAY( p0_n + dir + dir.Perpendicular(), p0_n + dir, diagColl ) );
@@ -688,8 +701,8 @@ void DP_GATEWAYS::BuildGeneric( const VECTOR2I& p0_p, const VECTOR2I& p0_n, bool
                     if( m != p0_p && m != p0_n )
                     {
                         int prio = ( padDist > padToGapThreshold * m_gap ? 10 : 20 );
-                        VECTOR2I g_p( ( p0_p - m ).Resize( (double) m_gap * M_SQRT1_2 ) );
-                        VECTOR2I g_n( ( p0_n - m ).Resize( (double) m_gap * M_SQRT1_2 ) );
+                        VECTOR2I g_p( ( p0_p - m ).Resize( ceil( (double) m_gap * M_SQRT1_2 ) ) );
+                        VECTOR2I g_n( ( p0_n - m ).Resize( ceil( (double) m_gap * M_SQRT1_2 ) ) );
 
                         m_gateways.push_back( DP_GATEWAY( m + g_p, m + g_n, k == 0 ? true : false, DIRECTION_45::ANG_OBTUSE, prio ) );
                     }
@@ -710,14 +723,14 @@ void DP_GATEWAYS::BuildGeneric( const VECTOR2I& p0_p, const VECTOR2I& p0_n, bool
                     {
                         VECTOR2I g_p, g_n;
 
-                        g_p = ( p0_p - m ).Resize( (double) m_gap * M_SQRT2 );
-                        g_n = ( p0_n - m ).Resize( (double) m_gap );
+                        g_p = ( p0_p - m ).Resize( ceil( (double) m_gap * M_SQRT2 ) );
+                        g_n = ( p0_n - m ).Resize( ceil( (double) m_gap ) );
 
                         if( angle( g_p, g_n ) != DIRECTION_45::ANG_ACUTE )
                             m_gateways.push_back( DP_GATEWAY( m + g_p, m + g_n, true ) );
 
                         g_p = ( p0_p - m ).Resize( m_gap );
-                        g_n = ( p0_n - m ).Resize( (double) m_gap * M_SQRT2 );
+                        g_n = ( p0_n - m ).Resize( ceil( (double) m_gap * M_SQRT2 ) );
 
                         if( angle( g_p, g_n ) != DIRECTION_45::ANG_ACUTE )
                             m_gateways.push_back( DP_GATEWAY( m + g_p, m + g_n, true ) );
diff --git a/pcbnew/router/pns_kicad_iface.h b/pcbnew/router/pns_kicad_iface.h
index 0d65847..361f579 100644
--- a/pcbnew/router/pns_kicad_iface.h
+++ b/pcbnew/router/pns_kicad_iface.h
@@ -76,7 +76,6 @@ private:
     PNS::NODE* m_world;
     PNS::ROUTER* m_router;
     BOARD* m_board;
-    PICKED_ITEMS_LIST m_undoBuffer;
     PCB_EDIT_FRAME* m_frame;
     std::unique_ptr<BOARD_COMMIT> m_commit;
     DISPLAY_OPTIONS* m_dispOptions;
-- 
1.9.1