Fix observed ghosts: https://github.com/tompi/cheapino/issues/33

keyboards/cheapino/config.h

@@ -35,3 +35,5 @@
 
 
 #define MAX_DEFERRED_EXECUTORS 32
+
+// #define DEBUG_MATRIX_SCAN_RATE

keyboards/cheapino/ghosting.c

@@ -0,0 +1,96 @@
+//
+// Created by Thomas Haukland on 2024-05-05.
+//
+
+#include "matrix.h"
+#include "quantum.h"
+#include "print.h"
+
+// This is just to be able to declare constants as they appear in the qmk console
+#define rev(b) \
+            ((b & 1) << 15) | \
+            ((b & (1 << 1)) << 13) | \
+            ((b & (1 << 2)) << 11) | \
+            ((b & (1 << 3)) << 9) | \
+            ((b & (1 << 4)) << 7) | \
+            ((b & (1 << 5)) << 5) | \
+            ((b & (1 << 6)) << 3) | \
+            ((b & (1 << 7)) << 1) | \
+            ((b & (1 << 8)) >> 1) | \
+            ((b & (1 << 9)) >> 3) | \
+            ((b & (1 << 10)) >> 5) | \
+            ((b & (1 << 11)) >> 7) | \
+            ((b & (1 << 12)) >> 9) | \
+            ((b & (1 << 13)) >> 11) | \
+            ((b & (1 << 14)) >> 13) | \
+            b >> 15
+
+/* This is for debugging the matrix rows
+void printBits(uint16_t n)
+{
+    long i;
+    for (i = 15; i >= 0; i--) {
+        if ((n & (1 << i)) != 0) {
+            printf("1");
+        }
+        else {
+            printf("0");
+        }
+    }
+    printf("\n");
+}
+*/
+
+bool bit_pattern_set(uint16_t number, uint16_t bitPattern) {
+    return !(~number & bitPattern);
+}
+
+void fix_ghosting_instance(
+        matrix_row_t current_matrix[],
+        ushort row_num_with_possible_error_cause,
+        uint16_t possible_error_cause,
+        ushort row_num_with_possible_error,
+        uint16_t possible_error,
+        uint16_t error_fix) {
+    if (bit_pattern_set(current_matrix[row_num_with_possible_error_cause], possible_error_cause)) {
+        if (bit_pattern_set(current_matrix[row_num_with_possible_error], possible_error)) {
+            current_matrix[row_num_with_possible_error] = current_matrix[row_num_with_possible_error] ^ error_fix;
+        }
+    }
+}
+
+void fix_ghosting_column(
+        matrix_row_t matrix[],
+        uint16_t possible_error_cause,
+        uint16_t possible_error,
+        uint16_t error_fix) {
+    // First the right side
+    for (short i = 0; i<3; i++) {
+        fix_ghosting_instance(matrix, i, possible_error_cause, (i+1)%3, possible_error, error_fix);
+        fix_ghosting_instance(matrix, i, possible_error_cause, (i+2)%3, possible_error, error_fix);
+    }
+
+    // Then exactly same procedure on the left side
+    for (short i = 0; i<3; i++) {
+        fix_ghosting_instance(matrix, i+4, possible_error_cause<<6, 4+((i+1)%3), possible_error<<6, error_fix<<6);
+        fix_ghosting_instance(matrix, i+4, possible_error_cause<<6, 4+((i+2)%3), possible_error<<6, error_fix<<6);
+    }
+}
+
+// For QWERTY layout, key combo a+s+e also outputs q. This suppresses the q, and other similar ghosts
+// These are observed ghosts(following a pattern). TODO: need to fix this for v3
+// Might need to add 2 diodes(one in each direction) for every row, to increase voltage drop.
+void fix_ghosting(matrix_row_t matrix[]) {
+    fix_ghosting_column(matrix, rev(0B0110000000000000), rev(0B1010000000000000), rev(0B1000000000000000));
+    fix_ghosting_column(matrix, rev(0B0110000000000000), rev(0B0101000000000000), rev(0B0001000000000000));
+
+    fix_ghosting_column(matrix, rev(0B0001100000000000), rev(0B0010100000000000), rev(0B0010000000000000));
+    fix_ghosting_column(matrix, rev(0B0001100000000000), rev(0B0001010000000000), rev(0B0000010000000000));
+
+    fix_ghosting_column(matrix, rev(0B1000010000000000), rev(0B1000100000000000), rev(0B1000000000000000));
+    fix_ghosting_column(matrix, rev(0B1000010000000000), rev(0B0100010000000000), rev(0B0000010000000000));
+
+    fix_ghosting_column(matrix, rev(0B1001000000000000), rev(0B0101000000000000), rev(0B0001000000000000));
+
+    fix_ghosting_column(matrix, rev(0B0100100000000000), rev(0B0100010000000000), rev(0B0100000000000000));
+}

keyboards/cheapino/ghosting.h

@@ -0,0 +1,5 @@
+//
+// Created by Thomas Haukland on 2024-05-05.
+//
+
+void fix_ghosting(matrix_row_t current_matrix[]);

keyboards/cheapino/matrix.c

@@ -26,10 +26,13 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "quantum.h"
 #include "debounce.h"
 #include "encoder.h"
+#include "ghosting.h"
 #include "print.h"
 
 // How long the scanning code waits for changed io to settle.
-#define MATRIX_IO_DELAY 30
+// Adjust from default 30 to weigh up for increased time spent ghost-hunting.
+// (the rp2040 does not seem to have any problems with this value...)
+#define MATRIX_IO_DELAY 25
 
 #define COL_SHIFTER ((uint16_t)1)
 
@@ -142,6 +145,8 @@ bool matrix_scan_custom(matrix_row_t current_matrix[]) {
 
     fix_encoder_action(current_matrix);
 
+    fix_ghosting(current_matrix);
+
     return has_matrix_changed(current_matrix);
 }
 

keyboards/cheapino/rules.mk

@@ -4,4 +4,5 @@ WS2812_DRIVER = vendor
 RGBLIGHT_ENABLE = yes
 DEFERRED_EXEC_ENABLE = yes
 SRC += encoder.c
+SRC += ghosting.c
 SRC += matrix.c