Try with another shield

build.yaml

@@ -19,6 +19,6 @@
 ---
 include:
   - board: nice_nano_v2
-    shield: abyss_left
+    shield: urchin_left
   - board: nice_nano_v2
-    shield: abyss_right
+    shield: urchin_right

config/boards/shields/urchin/Kconfig.defconfig

@@ -0,0 +1,17 @@
+# Copyright (c) 2022 Duccio Breschi
+# SPDX-License-Identifier: MIT
+
+if SHIELD_URCHIN_LEFT
+
+config ZMK_KEYBOARD_NAME
+    default "urchin"
+
+config ZMK_SPLIT_ROLE_CENTRAL
+    default y
+
+endif
+
+if SHIELD_URCHIN_LEFT || SHIELD_URCHIN_RIGHT
+config ZMK_SPLIT
+    default y
+endif

config/boards/shields/urchin/Kconfig.shield

@@ -0,0 +1,8 @@
+# Copyright (c) 2022 Duccio Breschi
+# SPDX-License-Identifier: MIT
+
+config SHIELD_URCHIN_LEFT
+    def_bool $(shields_list_contains,urchin_left)
+
+config SHIELD_URCHIN_RIGHT
+    def_bool $(shields_list_contains,urchin_right)

config/boards/shields/urchin/urchin.dtsi

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2022 Duccio Breschi
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <dt-bindings/zmk/matrix_transform.h>
+
+
+/ {
+    chosen {
+        zmk,kscan = &kscan0;
+        zmk,matrix_transform = &default_transform;
+    };
+
+    default_transform: keymap_transform_0 {
+        compatible = "zmk,matrix-transform";
+        columns = <10>;
+        rows = <4>;
+
+        map = <
+            RC(0,0)     RC(0,1)     RC(0,2)     RC(0,3)     RC(0,4)         RC(0,5)     RC(0,6)     RC(0,7)     RC(0,8 )    RC(0,9)
+            RC(1,0)     RC(1,1)     RC(1,2)     RC(1,3)     RC(1,4)         RC(1,5)     RC(1,6)     RC(1,7)     RC(1,8)     RC(1,9)
+            RC(2,0)     RC(2,1)     RC(2,2)     RC(2,3)     RC(2,4)         RC(2,5)     RC(2,6)     RC(2,7)     RC(2,8)     RC(2,9)
+                                                RC(3,3)     RC(3,4)         RC(3,5)     RC(3,6)
+        >;
+    };
+
+    kscan0: kscan {        
+        compatible = "zmk,kscan-gpio-matrix";
+        label = "KSCAN0";
+    };
+};

config/boards/shields/urchin/urchin.keymap

@@ -0,0 +1,7 @@
+/*
+ * Copyright (c) 2020 Duccio Breschi
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "../../../urchin.keymap"

config/boards/shields/urchin/urchin.zmk.yml

@@ -0,0 +1,11 @@
+file_format: "1"
+id: urchin
+name: urchin
+type: shield
+url: https://github.com/duckyb/urchin
+requires: [pro_micro]
+features:
+  - keys
+siblings:
+  - urchin_left
+  - urchin_right

config/boards/shields/urchin/urchin_left.overlay

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2022 Duccio Breschi
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "urchin.dtsi"
+
+&kscan0 {
+    diode-direction = "col2row";
+    col-gpios
+        = <&pro_micro 18 (GPIO_ACTIVE_HIGH)> // COL0
+        , <&pro_micro 15 (GPIO_ACTIVE_HIGH)> // COL1
+        , <&pro_micro 14 (GPIO_ACTIVE_HIGH)> // COL2
+        , <&pro_micro 16 (GPIO_ACTIVE_HIGH)> // COL3
+        , <&pro_micro 10 (GPIO_ACTIVE_HIGH)> // COL4
+    ;
+    row-gpios
+        = <&pro_micro 6 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)> // ROW0
+        , <&pro_micro 7 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)> // ROW1
+        , <&pro_micro 8 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)> // ROW2
+        , <&pro_micro 9 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)> // ROW3
+    ;
+};

config/boards/shields/urchin/urchin_right.overlay

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2022 Duccio Breschi
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "urchin.dtsi"
+
+&default_transform {
+    col-offset = <5>;
+};
+
+&kscan0 {
+    diode-direction = "col2row";
+    col-gpios
+        = <&pro_micro 5 (GPIO_ACTIVE_HIGH)> // COL0
+        , <&pro_micro 6 (GPIO_ACTIVE_HIGH)> // COL1
+        , <&pro_micro 7 (GPIO_ACTIVE_HIGH)> // COL2
+        , <&pro_micro 8 (GPIO_ACTIVE_HIGH)> // COL3
+        , <&pro_micro 9 (GPIO_ACTIVE_HIGH)> // COL4
+    ;
+    row-gpios
+        = <&pro_micro 15 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)> // ROW0
+        , <&pro_micro 14 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)> // ROW1
+        , <&pro_micro 16 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)> // ROW2
+        , <&pro_micro 10 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)> // ROW3
+    ;
+};