Asymmetric encoders, encoder tests. (#16068)

27 files changed, 921 insertions, 138 deletions

diff --git a/builddefs/build_test.mk b/builddefs/build_test.mk
index 7226004aab..5ad33b19c5 100644
--- a/builddefs/build_test.mk
+++ b/builddefs/build_test.mk
@@ -4,6 +4,8 @@ endif
 
 .DEFAULT_GOAL := all
 
+OPT = g
+
 include paths.mk
 include $(BUILDDEFS_PATH)/message.mk
 
diff --git a/builddefs/testlist.mk b/builddefs/testlist.mk
index 86da5668ac..b8d22bce80 100644
--- a/builddefs/testlist.mk
+++ b/builddefs/testlist.mk
@@ -2,6 +2,7 @@ TEST_LIST = $(sort $(patsubst %/test.mk,%, $(shell find $(ROOT_DIR)tests -type f
 FULL_TESTS := $(notdir $(TEST_LIST))
 
 include $(QUANTUM_PATH)/debounce/tests/testlist.mk
+include $(QUANTUM_PATH)/encoder/tests/testlist.mk
 include $(QUANTUM_PATH)/sequencer/tests/testlist.mk
 include $(PLATFORM_PATH)/test/testlist.mk
 
diff --git a/docs/feature_encoders.md b/docs/feature_encoders.md
index 6a1a3750a6..f71c7e7325 100644
--- a/docs/feature_encoders.md
+++ b/docs/feature_encoders.md
@@ -54,6 +54,19 @@ If you are using different pinouts for the encoders on each half of a split keyb
 #define ENCODER_RESOLUTIONS_RIGHT { 2, 4 }
 ```
 
+If the `_RIGHT` definitions aren't specified in your `config.h`, then the non-`_RIGHT` versions will be applied to both sides of the split.
+
+Additionally, if one side does not have an encoder, you can specify `{}` for the pins/resolution -- for example, a split keyboard with only a right-side encoder:
+
+```c
+#define ENCODERS_PAD_A { }
+#define ENCODERS_PAD_B { }
+#define ENCODER_RESOLUTIONS { }
+#define ENCODERS_PAD_A_RIGHT { B12 }
+#define ENCODERS_PAD_B_RIGHT { B13 }
+#define ENCODER_RESOLUTIONS_RIGHT { 4 }
+```
+
 ## Callbacks
 
 The callback functions can be inserted into your `<keyboard>.c`:
diff --git a/keyboards/draculad/config.h b/keyboards/draculad/config.h
index abcdc76b4b..3060f801c6 100644
--- a/keyboards/draculad/config.h
+++ b/keyboards/draculad/config.h
@@ -61,7 +61,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define ENCODERS_PAD_A {B2 , B4}
 #define ENCODERS_PAD_B {B6 , B5}
 
-#define ENCODER_RESOLUTIONS { 4, 4, 4, 1}
+#define ENCODER_RESOLUTIONS { 4, 4 }
+#define ENCODER_RESOLUTIONS_RIGHT { 4, 1 }
 #define UNUSED_PINS
 
 #define EE_HANDS
diff --git a/keyboards/sofle/keyhive/config.h b/keyboards/sofle/keyhive/config.h
index c934754e65..93048f3cd1 100755
--- a/keyboards/sofle/keyhive/config.h
+++ b/keyboards/sofle/keyhive/config.h
@@ -42,11 +42,12 @@
 #define DEBOUNCE        5
 
 // Encoder support
-#define ENCODERS_PAD_A       { F5 }
-#define ENCODERS_PAD_B       { F4 }
-#define ENCODERS_PAD_A_RIGHT { F4 }
-#define ENCODERS_PAD_B_RIGHT { F5 }
-#define ENCODER_RESOLUTIONS  { 4, 2 }  // Left encoder seems to have double-output issue but right does not.
+#define ENCODERS_PAD_A            { F5 }
+#define ENCODERS_PAD_B            { F4 }
+#define ENCODERS_PAD_A_RIGHT      { F4 }
+#define ENCODERS_PAD_B_RIGHT      { F5 }
+#define ENCODER_RESOLUTIONS       { 4 }
+#define ENCODER_RESOLUTIONS_RIGHT { 2 }  // Left encoder seems to have double-output issue but right does not.
 
 #define TAP_CODE_DELAY  10
 
diff --git a/keyboards/viktus/sp_mini/config.h b/keyboards/viktus/sp_mini/config.h
index 06b8c2f51a..ec13a240c2 100644
--- a/keyboards/viktus/sp_mini/config.h
+++ b/keyboards/viktus/sp_mini/config.h
@@ -35,7 +35,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 // wiring of each half
 #define MATRIX_ROW_PINS { F0, B5, B4, D7, D6 }
-#define MATRIX_COL_PINS { B6, C6, C7, D4, D2, D3, D5 } // no B7 on left hand
+#define MATRIX_COL_PINS { B6, C6, C7, D4, D2, D3, D5, NO_PIN } // no B7 on left hand
 #define MATRIX_ROW_PINS_RIGHT { F0, B5, B4, D7, D6 }
 #define MATRIX_COL_PINS_RIGHT { B6, C6, C7, D4, D2, D3, D5, B7 }
 
@@ -78,7 +78,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 //#define ENCODERS_PAD_A_RIGHT {F4}
 //#define ENCODERS_PAD_B_RIGHT {F1}
 
-#define ENCODER_RESOLUTIONS { 8, 8 }
+#define ENCODER_RESOLUTIONS { 8 }
 
 /*
  * Feature disable options
diff --git a/quantum/encoder.c b/quantum/encoder.c
index 438c7d8564..0a3d6f577c 100644
--- a/quantum/encoder.c
+++ b/quantum/encoder.c
@@ -31,11 +31,13 @@
 #    error "No encoder pads defined by ENCODERS_PAD_A and ENCODERS_PAD_B"
 #endif
 
-#define NUMBER_OF_ENCODERS (sizeof(encoders_pad_a) / sizeof(pin_t))
-static pin_t encoders_pad_a[] = ENCODERS_PAD_A;
-static pin_t encoders_pad_b[] = ENCODERS_PAD_B;
+extern volatile bool isLeftHand;
+
+static pin_t encoders_pad_a[NUM_ENCODERS_MAX_PER_SIDE] = ENCODERS_PAD_A;
+static pin_t encoders_pad_b[NUM_ENCODERS_MAX_PER_SIDE] = ENCODERS_PAD_B;
+
 #ifdef ENCODER_RESOLUTIONS
-static uint8_t encoder_resolutions[] = ENCODER_RESOLUTIONS;
+static uint8_t encoder_resolutions[NUM_ENCODERS] = ENCODER_RESOLUTIONS;
 #endif
 
 #ifndef ENCODER_DIRECTION_FLIP
@@ -47,18 +49,20 @@ static uint8_t encoder_resolutions[] = ENCODER_RESOLUTIONS;
 #endif
 static int8_t encoder_LUT[] = {0, -1, 1, 0, 1, 0, 0, -1, -1, 0, 0, 1, 0, 1, -1, 0};
 
-static uint8_t encoder_state[NUMBER_OF_ENCODERS]  = {0};
-static int8_t  encoder_pulses[NUMBER_OF_ENCODERS] = {0};
+static uint8_t encoder_state[NUM_ENCODERS]  = {0};
+static int8_t  encoder_pulses[NUM_ENCODERS] = {0};
 
+// encoder counts
+static uint8_t thisCount;
 #ifdef SPLIT_KEYBOARD
-// right half encoders come over as second set of encoders
-static uint8_t encoder_value[NUMBER_OF_ENCODERS * 2] = {0};
-// row offsets for each hand
+// encoder offsets for each hand
 static uint8_t thisHand, thatHand;
-#else
-static uint8_t encoder_value[NUMBER_OF_ENCODERS] = {0};
+// encoder counts for each hand
+static uint8_t thatCount;
 #endif
 
+static uint8_t encoder_value[NUM_ENCODERS] = {0};
+
 __attribute__((weak)) void encoder_wait_pullup_charge(void) {
     wait_us(100);
 }
@@ -72,36 +76,63 @@ __attribute__((weak)) bool encoder_update_kb(uint8_t index, bool clockwise) {
 }
 
 void encoder_init(void) {
+#ifdef SPLIT_KEYBOARD
+    thisHand  = isLeftHand ? 0 : NUM_ENCODERS_LEFT;
+    thatHand  = NUM_ENCODERS_LEFT - thisHand;
+    thisCount = isLeftHand ? NUM_ENCODERS_LEFT : NUM_ENCODERS_RIGHT;
+    thatCount = isLeftHand ? NUM_ENCODERS_RIGHT : NUM_ENCODERS_LEFT;
+#else // SPLIT_KEYBOARD
+    thisCount                = NUM_ENCODERS;
+#endif
+
+#ifdef ENCODER_TESTS
+    // Annoying that we have to clear out values during initialisation here, but
+    // because all the arrays are static locals, rerunning tests in the same
+    // executable doesn't reset any of these. Kinda crappy having test-only code
+    // here, but it's the simplest solution.
+    memset(encoder_value, 0, sizeof(encoder_value));
+    memset(encoder_state, 0, sizeof(encoder_state));
+    memset(encoder_pulses, 0, sizeof(encoder_pulses));
+    static const pin_t encoders_pad_a_left[] = ENCODERS_PAD_A;
+    static const pin_t encoders_pad_b_left[] = ENCODERS_PAD_B;
+    for (uint8_t i = 0; i < thisCount; i++) {
+        encoders_pad_a[i] = encoders_pad_a_left[i];
+        encoders_pad_b[i] = encoders_pad_b_left[i];
+    }
+#endif
+
 #if defined(SPLIT_KEYBOARD) && defined(ENCODERS_PAD_A_RIGHT) && defined(ENCODERS_PAD_B_RIGHT)
+    // Re-initialise the pads if it's the right-hand side
     if (!isLeftHand) {
-        const pin_t encoders_pad_a_right[] = ENCODERS_PAD_A_RIGHT;
-        const pin_t encoders_pad_b_right[] = ENCODERS_PAD_B_RIGHT;
-#    if defined(ENCODER_RESOLUTIONS_RIGHT)
-        const uint8_t encoder_resolutions_right[] = ENCODER_RESOLUTIONS_RIGHT;
-#    endif
-        for (uint8_t i = 0; i < NUMBER_OF_ENCODERS; i++) {
+        static const pin_t encoders_pad_a_right[] = ENCODERS_PAD_A_RIGHT;
+        static const pin_t encoders_pad_b_right[] = ENCODERS_PAD_B_RIGHT;
+        for (uint8_t i = 0; i < thisCount; i++) {
             encoders_pad_a[i] = encoders_pad_a_right[i];
             encoders_pad_b[i] = encoders_pad_b_right[i];
-#    if defined(ENCODER_RESOLUTIONS_RIGHT)
-            encoder_resolutions[i] = encoder_resolutions_right[i];
-#    endif
         }
     }
-#endif
+#endif // defined(SPLIT_KEYBOARD) && defined(ENCODERS_PAD_A_RIGHT) && defined(ENCODERS_PAD_B_RIGHT)
+
+    // Encoder resolutions is handled purely master-side, so concatenate the two arrays
+#if defined(SPLIT_KEYBOARD) && defined(ENCODER_RESOLUTIONS)
+#    if defined(ENCODER_RESOLUTIONS_RIGHT)
+    static const uint8_t encoder_resolutions_right[NUM_ENCODERS_RIGHT] = ENCODER_RESOLUTIONS_RIGHT;
+#    else  // defined(ENCODER_RESOLUTIONS_RIGHT)
+    static const uint8_t encoder_resolutions_right[NUM_ENCODERS_RIGHT] = ENCODER_RESOLUTIONS;
+#    endif // defined(ENCODER_RESOLUTIONS_RIGHT)
+    for (uint8_t i = 0; i < NUM_ENCODERS_RIGHT; i++) {
+        encoder_resolutions[NUM_ENCODERS_LEFT + i] = encoder_resolutions_right[i];
+    }
+#endif // defined(SPLIT_KEYBOARD) && defined(ENCODER_RESOLUTIONS)
 
-    for (int i = 0; i < NUMBER_OF_ENCODERS; i++) {
+    for (uint8_t i = 0; i < thisCount; i++) {
         setPinInputHigh(encoders_pad_a[i]);
         setPinInputHigh(encoders_pad_b[i]);
     }
     encoder_wait_pullup_charge();
-    for (int i = 0; i < NUMBER_OF_ENCODERS; i++) {
+    for (uint8_t i = 0; i < thisCount; i++) {
         encoder_state[i] = (readPin(encoders_pad_a[i]) << 0) | (readPin(encoders_pad_b[i]) << 1);
     }
-
-#ifdef SPLIT_KEYBOARD
-    thisHand = isLeftHand ? 0 : NUMBER_OF_ENCODERS;
-    thatHand = NUMBER_OF_ENCODERS - thisHand;
-#endif
 }
 
 static bool encoder_update(uint8_t index, uint8_t state) {
@@ -109,9 +140,9 @@ static bool encoder_update(uint8_t index, uint8_t state) {
     uint8_t i       = index;
 
 #ifdef ENCODER_RESOLUTIONS
-    uint8_t resolution = encoder_resolutions[i];
+    const uint8_t resolution = encoder_resolutions[i];
 #else
-    uint8_t resolution = ENCODER_RESOLUTION;
+    const uint8_t resolution = ENCODER_RESOLUTION;
 #endif
 
 #ifdef SPLIT_KEYBOARD
@@ -139,10 +170,13 @@ static bool encoder_update(uint8_t index, uint8_t state) {
 
 bool encoder_read(void) {
     bool changed = false;
-    for (uint8_t i = 0; i < NUMBER_OF_ENCODERS; i++) {
-        encoder_state[i] <<= 2;
-        encoder_state[i] |= (readPin(encoders_pad_a[i]) << 0) | (readPin(encoders_pad_b[i]) << 1);
-        changed |= encoder_update(i, encoder_state[i]);
+    for (uint8_t i = 0; i < thisCount; i++) {
+        uint8_t new_status = (readPin(encoders_pad_a[i]) << 0) | (readPin(encoders_pad_b[i]) << 1);
+        if ((encoder_state[i] & 0x3) != new_status) {
+            encoder_state[i] <<= 2;
+            encoder_state[i] |= new_status;
+            changed |= encoder_update(i, encoder_state[i]);
+        }
     }
     return changed;
 }
@@ -150,15 +184,15 @@ bool encoder_read(void) {
 #ifdef SPLIT_KEYBOARD
 void last_encoder_activity_trigger(void);
 
-void encoder_state_raw(uint8_t* slave_state) {
-    memcpy(slave_state, &encoder_value[thisHand], sizeof(uint8_t) * NUMBER_OF_ENCODERS);
+void encoder_state_raw(uint8_t *slave_state) {
+    memcpy(slave_state, &encoder_value[thisHand], sizeof(uint8_t) * thisCount);
 }
 
-void encoder_update_raw(uint8_t* slave_state) {
+void encoder_update_raw(uint8_t *slave_state) {
     bool changed = false;
-    for (uint8_t i = 0; i < NUMBER_OF_ENCODERS; i++) {
-        uint8_t index = i + thatHand;
-        int8_t  delta = slave_state[i] - encoder_value[index];
+    for (uint8_t i = 0; i < thatCount; i++) { // Note inverted logic -- we want the opposite side
+        const uint8_t index = i + thatHand;
+        int8_t        delta = slave_state[i] - encoder_value[index];
         while (delta > 0) {
             delta--;
             encoder_value[index]++;
diff --git a/quantum/encoder.h b/quantum/encoder.h
index 25dc77721d..dd6db14629 100644
--- a/quantum/encoder.h
+++ b/quantum/encoder.h
@@ -18,6 +18,7 @@
 #pragma once
 
 #include "quantum.h"
+#include "util.h"
 
 void encoder_init(void);
 bool encoder_read(void);
@@ -26,6 +27,31 @@ bool encoder_update_kb(uint8_t index, bool clockwise);
 bool encoder_update_user(uint8_t index, bool clockwise);
 
 #ifdef SPLIT_KEYBOARD
+
 void encoder_state_raw(uint8_t* slave_state);
 void encoder_update_raw(uint8_t* slave_state);
-#endif
+
+#    if defined(ENCODERS_PAD_A_RIGHT)
+#        define NUM_ENCODERS_LEFT (sizeof(((pin_t[])ENCODERS_PAD_A)) / sizeof(pin_t))
+#        define NUM_ENCODERS_RIGHT (sizeof(((pin_t[])ENCODERS_PAD_A_RIGHT)) / sizeof(pin_t))
+#    else
+#        define NUM_ENCODERS_LEFT (sizeof(((pin_t[])ENCODERS_PAD_A)) / sizeof(pin_t))
+#        define NUM_ENCODERS_RIGHT NUM_ENCODERS_LEFT
+#    endif
+#    define NUM_ENCODERS (NUM_ENCODERS_LEFT + NUM_ENCODERS_RIGHT)
+
+#else // SPLIT_KEYBOARD
+
+#    define NUM_ENCODERS (sizeof(((pin_t[])ENCODERS_PAD_A)) / sizeof(pin_t))
+#    define NUM_ENCODERS_LEFT NUM_ENCODERS
+#    define NUM_ENCODERS_RIGHT 0
+
+#endif // SPLIT_KEYBOARD
+
+#ifndef NUM_ENCODERS
+#    define NUM_ENCODERS 0
+#    define NUM_ENCODERS_LEFT 0
+#    define NUM_ENCODERS_RIGHT 0
+#endif // NUM_ENCODERS
+
+#define NUM_ENCODERS_MAX_PER_SIDE MAX(NUM_ENCODERS_LEFT, NUM_ENCODERS_RIGHT)
diff --git a/quantum/encoder/tests/config_mock.h b/quantum/encoder/tests/config_mock.h
new file mode 100644
index 0000000000..703dcaf103
--- /dev/null
+++ b/quantum/encoder/tests/config_mock.h
@@ -0,0 +1,22 @@
+// Copyright 2022 Nick Brassel (@tzarc)
+// SPDX-License-Identifier: GPL-2.0-or-later
+#pragma once
+
+#define MATRIX_ROWS 1
+#define MATRIX_COLS 1
+
+/* Here, "pins" from 0 to 31 are allowed. */
+#define ENCODERS_PAD_A \
+    { 0 }
+#define ENCODERS_PAD_B \
+    { 1 }
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "mock.h"
+
+#ifdef __cplusplus
+};
+#endif
diff --git a/quantum/encoder/tests/config_mock_split_left_eq_right.h b/quantum/encoder/tests/config_mock_split_left_eq_right.h
new file mode 100644
index 0000000000..c80ac4d519
--- /dev/null
+++ b/quantum/encoder/tests/config_mock_split_left_eq_right.h
@@ -0,0 +1,26 @@
+// Copyright 2022 Nick Brassel (@tzarc)
+// SPDX-License-Identifier: GPL-2.0-or-later
+#pragma once
+
+#define MATRIX_ROWS 1
+#define MATRIX_COLS 1
+
+/* Here, "pins" from 0 to 31 are allowed. */
+#define ENCODERS_PAD_A \
+    { 0, 2 }
+#define ENCODERS_PAD_B \
+    { 1, 3 }
+#define ENCODERS_PAD_A_RIGHT \
+    { 4, 6 }
+#define ENCODERS_PAD_B_RIGHT \
+    { 5, 7 }
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "mock_split.h"
+
+#ifdef __cplusplus
+};
+#endif
diff --git a/quantum/encoder/tests/config_mock_split_left_gt_right.h b/quantum/encoder/tests/config_mock_split_left_gt_right.h
new file mode 100644
index 0000000000..91d5f3d605
--- /dev/null
+++ b/quantum/encoder/tests/config_mock_split_left_gt_right.h
@@ -0,0 +1,26 @@
+// Copyright 2022 Nick Brassel (@tzarc)
+// SPDX-License-Identifier: GPL-2.0-or-later
+#pragma once
+
+#define MATRIX_ROWS 1
+#define MATRIX_COLS 1
+
+/* Here, "pins" from 0 to 31 are allowed. */
+#define ENCODERS_PAD_A \
+    { 0, 2, 4 }
+#define ENCODERS_PAD_B \
+    { 1, 3, 5 }
+#define ENCODERS_PAD_A_RIGHT \
+    { 6, 8 }
+#define ENCODERS_PAD_B_RIGHT \
+    { 7, 9 }
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "mock_split.h"
+
+#ifdef __cplusplus
+};
+#endif
diff --git a/quantum/encoder/tests/config_mock_split_left_lt_right.h b/quantum/encoder/tests/config_mock_split_left_lt_right.h
new file mode 100644
index 0000000000..4108a184a6
--- /dev/null
+++ b/quantum/encoder/tests/config_mock_split_left_lt_right.h
@@ -0,0 +1,26 @@
+// Copyright 2022 Nick Brassel (@tzarc)
+// SPDX-License-Identifier: GPL-2.0-or-later
+#pragma once
+
+#define MATRIX_ROWS 1
+#define MATRIX_COLS 1
+
+/* Here, "pins" from 0 to 31 are allowed. */
+#define ENCODERS_PAD_A \
+    { 0, 2 }
+#define ENCODERS_PAD_B \
+    { 1, 3 }
+#define ENCODERS_PAD_A_RIGHT \
+    { 4, 6, 8 }
+#define ENCODERS_PAD_B_RIGHT \
+    { 5, 7, 9 }
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "mock_split.h"
+
+#ifdef __cplusplus
+};
+#endif
diff --git a/quantum/encoder/tests/config_mock_split_no_left.h b/quantum/encoder/tests/config_mock_split_no_left.h
new file mode 100644
index 0000000000..9db7fa7e41
--- /dev/null
+++ b/quantum/encoder/tests/config_mock_split_no_left.h
@@ -0,0 +1,26 @@
+// Copyright 2022 Nick Brassel (@tzarc)
+// SPDX-License-Identifier: GPL-2.0-or-later
+#pragma once
+
+#define MATRIX_ROWS 1
+#define MATRIX_COLS 1
+
+/* Here, "pins" from 0 to 31 are allowed. */
+#define ENCODERS_PAD_A \
+    {}
+#define ENCODERS_PAD_B \
+    {}
+#define ENCODERS_PAD_A_RIGHT \
+    { 0, 2 }
+#define ENCODERS_PAD_B_RIGHT \
+    { 1, 3 }
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "mock_split.h"
+
+#ifdef __cplusplus
+};
+#endif
diff --git a/quantum/encoder/tests/config_mock_split_no_right.h b/quantum/encoder/tests/config_mock_split_no_right.h
new file mode 100644
index 0000000000..14f18015e6
--- /dev/null
+++ b/quantum/encoder/tests/config_mock_split_no_right.h
@@ -0,0 +1,26 @@
+// Copyright 2022 Nick Brassel (@tzarc)
+// SPDX-License-Identifier: GPL-2.0-or-later
+#pragma once
+
+#define MATRIX_ROWS 1
+#define MATRIX_COLS 1
+
+/* Here, "pins" from 0 to 31 are allowed. */
+#define ENCODERS_PAD_A \
+    { 0, 2 }
+#define ENCODERS_PAD_B \
+    { 1, 3 }
+#define ENCODERS_PAD_A_RIGHT \
+    {}
+#define ENCODERS_PAD_B_RIGHT \
+    {}
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "mock_split.h"
+
+#ifdef __cplusplus
+};
+#endif
diff --git a/quantum/encoder/tests/encoder_tests.cpp b/quantum/encoder/tests/encoder_tests.cpp
index 1888fdab8d..b7c18aeec0 100644
--- a/quantum/encoder/tests/encoder_tests.cpp
+++ b/quantum/encoder/tests/encoder_tests.cpp
@@ -30,12 +30,12 @@ struct update {
     bool   clockwise;
 };
 
-uint8_t uidx = 0;
+uint8_t updates_array_idx = 0;
 update  updates[32];
 
 bool encoder_update_kb(uint8_t index, bool clockwise) {
-    updates[uidx % 32] = {index, clockwise};
-    uidx++;
+    updates[updates_array_idx % 32] = {index, clockwise};
+    updates_array_idx++;
     return true;
 }
 
@@ -47,15 +47,15 @@ bool setAndRead(pin_t pin, bool val) {
 class EncoderTest : public ::testing::Test {};
 
 TEST_F(EncoderTest, TestInit) {
-    uidx = 0;
+    updates_array_idx = 0;
     encoder_init();
     EXPECT_EQ(pinIsInputHigh[0], true);
     EXPECT_EQ(pinIsInputHigh[1], true);
-    EXPECT_EQ(uidx, 0);
+    EXPECT_EQ(updates_array_idx, 0);
 }
 
 TEST_F(EncoderTest, TestOneClockwise) {
-    uidx = 0;
+    updates_array_idx = 0;
     encoder_init();
     // send 4 pulses. with resolution 4, that's one step and we should get 1 update.
     setAndRead(0, false);
@@ -63,26 +63,26 @@ TEST_F(EncoderTest, TestOneClockwise) {
     setAndRead(0, true);
     setAndRead(1, true);
 
-    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates_array_idx, 1);
     EXPECT_EQ(updates[0].index, 0);
     EXPECT_EQ(updates[0].clockwise, true);
 }
 
 TEST_F(EncoderTest, TestOneCounterClockwise) {
-    uidx = 0;
+    updates_array_idx = 0;
     encoder_init();
     setAndRead(1, false);
     setAndRead(0, false);
     setAndRead(1, true);
     setAndRead(0, true);
 
-    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates_array_idx, 1);
     EXPECT_EQ(updates[0].index, 0);
     EXPECT_EQ(updates[0].clockwise, false);
 }
 
 TEST_F(EncoderTest, TestTwoClockwiseOneCC) {
-    uidx = 0;
+    updates_array_idx = 0;
     encoder_init();
     setAndRead(0, false);
     setAndRead(1, false);
@@ -97,7 +97,7 @@ TEST_F(EncoderTest, TestTwoClockwiseOneCC) {
     setAndRead(1, true);
     setAndRead(0, true);
 
-    EXPECT_EQ(uidx, 3);
+    EXPECT_EQ(updates_array_idx, 3);
     EXPECT_EQ(updates[0].index, 0);
     EXPECT_EQ(updates[0].clockwise, true);
     EXPECT_EQ(updates[1].index, 0);
@@ -107,38 +107,38 @@ TEST_F(EncoderTest, TestTwoClockwiseOneCC) {
 }
 
 TEST_F(EncoderTest, TestNoEarly) {
-    uidx = 0;
+    updates_array_idx = 0;
     encoder_init();
     // send 3 pulses. with resolution 4, that's not enough for a step.
     setAndRead(0, false);
     setAndRead(1, false);
     setAndRead(0, true);
-    EXPECT_EQ(uidx, 0);
+    EXPECT_EQ(updates_array_idx, 0);
     // now send last pulse
     setAndRead(1, true);
-    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates_array_idx, 1);
     EXPECT_EQ(updates[0].index, 0);
     EXPECT_EQ(updates[0].clockwise, true);
 }
 
 TEST_F(EncoderTest, TestHalfway) {
-    uidx = 0;
+    updates_array_idx = 0;
     encoder_init();
     // go halfway
     setAndRead(0, false);
     setAndRead(1, false);
-    EXPECT_EQ(uidx, 0);
+    EXPECT_EQ(updates_array_idx, 0);
     // back off
     setAndRead(1, true);
     setAndRead(0, true);
-    EXPECT_EQ(uidx, 0);
+    EXPECT_EQ(updates_array_idx, 0);
     // go all the way
     setAndRead(0, false);
     setAndRead(1, false);
     setAndRead(0, true);
     setAndRead(1, true);
     // should result in 1 update
-    EXPECT_EQ(uidx, 1);
+    EXPECT_EQ(updates_array_idx, 1);
     EXPECT_EQ(updates[0].index, 0);
     EXPECT_EQ(updates[0].clockwise, true);
 }
diff --git a/quantum/encoder/tests/encoder_tests_split_left_eq_right.cpp b/quantum/encoder/tests/encoder_tests_split_left_eq_right.cpp
new file mode 100644
index 0000000000..916e47b185
--- /dev/null
+++ b/quantum/encoder/tests/encoder_tests_split_left_eq_right.cpp
@@ -0,0 +1,135 @@
+/* Copyright 2021 Balz Guenat
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "gtest/gtest.h"
+#include "gmock/gmock.h"
+#include <vector>
+#include <algorithm>
+#include <stdio.h>
+
+extern "C" {
+#include "encoder.h"
+#include "encoder/tests/mock_split.h"
+}
+
+struct update {
+    int8_t index;
+    bool   clockwise;
+};
+
+uint8_t updates_array_idx = 0;
+update  updates[32];
+
+bool isLeftHand;
+
+bool encoder_update_kb(uint8_t index, bool clockwise) {
+    if (!isLeftHand) {
+        // this method has no effect on slave half
+        printf("ignoring update on right hand (%d,%s)\n", index, clockwise ? "CW" : "CC");
+        return true;
+    }
+    updates[updates_array_idx % 32] = {index, clockwise};
+    updates_array_idx++;
+    return true;
+}
+
+bool setAndRead(pin_t pin, bool val) {
+    setPin(pin, val);
+    return encoder_read();
+}
+
+class EncoderSplitTestLeftEqRight : public ::testing::Test {
+   protected:
+    void SetUp() override {
+        updates_array_idx = 0;
+        for (int i = 0; i < 32; i++) {
+            pinIsInputHigh[i] = 0;
+            pins[i]           = 0;
+        }
+    }
+};
+
+TEST_F(EncoderSplitTestLeftEqRight, TestInitLeft) {
+    isLeftHand = true;
+    encoder_init();
+    EXPECT_EQ(pinIsInputHigh[0], true);
+    EXPECT_EQ(pinIsInputHigh[1], true);
+    EXPECT_EQ(pinIsInputHigh[2], true);
+    EXPECT_EQ(pinIsInputHigh[3], true);
+    EXPECT_EQ(pinIsInputHigh[4], false);
+    EXPECT_EQ(pinIsInputHigh[5], false);
+    EXPECT_EQ(pinIsInputHigh[6], false);
+    EXPECT_EQ(pinIsInputHigh[7], false);
+    EXPECT_EQ(updates_array_idx, 0); // no updates received
+}
+
+TEST_F(EncoderSplitTestLeftEqRight, TestInitRight) {
+    isLeftHand = false;
+    encoder_init();
+    EXPECT_EQ(pinIsInputHigh[0], false);
+    EXPECT_EQ(pinIsInputHigh[1], false);
+    EXPECT_EQ(pinIsInputHigh[2], false);
+    EXPECT_EQ(pinIsInputHigh[3], false);
+    EXPECT_EQ(pinIsInputHigh[4], true);
+    EXPECT_EQ(pinIsInputHigh[5], true);
+    EXPECT_EQ(pinIsInputHigh[6], true);
+    EXPECT_EQ(pinIsInputHigh[7], true);
+    EXPECT_EQ(updates_array_idx, 0); // no updates received
+}
+
+TEST_F(EncoderSplitTestLeftEqRight, TestOneClockwiseLeft) {
+    isLeftHand = true;
+    encoder_init();
+    // send 4 pulses. with resolution 4, that's one step and we should get 1 update.
+    setAndRead(0, false);
+    setAndRead(1, false);
+    setAndRead(0, true);
+    setAndRead(1, true);
+
+    EXPECT_EQ(updates_array_idx, 1); // one update received
+    EXPECT_EQ(updates[0].index, 0);
+    EXPECT_EQ(updates[0].clockwise, true);
+}
+
+TEST_F(EncoderSplitTestLeftEqRight, TestOneClockwiseRightSent) {
+    isLeftHand = false;
+    encoder_init();
+    // send 4 pulses. with resolution 4, that's one step and we should get 1 update.
+    setAndRead(6, false);
+    setAndRead(7, false);
+    setAndRead(6, true);
+    setAndRead(7, true);
+
+    uint8_t slave_state[32] = {0};
+    encoder_state_raw(slave_state);
+
+    EXPECT_EQ(slave_state[0], 0);
+    EXPECT_EQ(slave_state[1], 0xFF);
+}
+
+TEST_F(EncoderSplitTestLeftEqRight, TestMultipleEncodersRightReceived) {
+    isLeftHand = true;
+    encoder_init();
+
+    uint8_t slave_state[32] = {1, 0xFF}; // First right encoder is CCW, Second right encoder CW
+    encoder_update_raw(slave_state);
+
+    EXPECT_EQ(updates_array_idx, 2); // two updates received, one for each changed item on the right side
+    EXPECT_EQ(updates[0].index, 2);
+    EXPECT_EQ(updates[0].clockwise, false);
+    EXPECT_EQ(updates[1].index, 3);
+    EXPECT_EQ(updates[1].clockwise, true);
+}
diff --git a/quantum/encoder/tests/encoder_tests_split_left_gt_right.cpp b/quantum/encoder/tests/encoder_tests_split_left_gt_right.cpp
new file mode 100644
index 0000000000..7b64bb2981
--- /dev/null
+++ b/quantum/encoder/tests/encoder_tests_split_left_gt_right.cpp
@@ -0,0 +1,139 @@
+/* Copyright 2021 Balz Guenat
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "gtest/gtest.h"
+#include "gmock/gmock.h"
+#include <vector>
+#include <algorithm>
+#include <stdio.h>
+
+extern "C" {
+#include "encoder.h"
+#include "encoder/tests/mock_split.h"
+}
+
+struct update {
+    int8_t index;
+    bool   clockwise;
+};
+
+uint8_t updates_array_idx = 0;
+update  updates[32];
+
+bool isLeftHand;
+
+bool encoder_update_kb(uint8_t index, bool clockwise) {
+    if (!isLeftHand) {
+        // this method has no effect on slave half
+        printf("ignoring update on right hand (%d,%s)\n", index, clockwise ? "CW" : "CC");
+        return true;
+    }
+    updates[updates_array_idx % 32] = {index, clockwise};
+    updates_array_idx++;
+    return true;
+}
+
+bool setAndRead(pin_t pin, bool val) {
+    setPin(pin, val);
+    return encoder_read();
+}
+
+class EncoderSplitTestLeftGreaterThanRight : public ::testing::Test {
+   protected:
+    void SetUp() override {
+        updates_array_idx = 0;
+        for (int i = 0; i < 32; i++) {
+            pinIsInputHigh[i] = 0;
+            pins[i]           = 0;
+        }
+    }
+};
+
+TEST_F(EncoderSplitTestLeftGreaterThanRight, TestInitLeft) {
+    isLeftHand = true;
+    encoder_init();
+