1 files changed, 86 insertions, 0 deletions
diff --git a/keyboards/torn/torn_encoder.c b/keyboards/torn/torn_encoder.c
new file mode 100644
index 000000000..ef9b0873f
--- /dev/null
+++ b/keyboards/torn/torn_encoder.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2020 Richard Titmuss <richard.titmuss@gmail.com>
+ * Copyright 2018 Jack Humbert <jack.humb@gmail.com>
+ *
+ * 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 "torn.h"
+#include "mcp23018.h"
+
+#ifndef ENCODER_RESOLUTION
+#    define ENCODER_RESOLUTION 4
+#endif
+
+#define ENCODER_CLOCKWISE true
+#define ENCODER_COUNTER_CLOCKWISE false
+
+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  = 0;
+static int8_t  encoder_pulses = 0;
+
+extern const uint16_t PROGMEM encoder_keymaps[][2][2];
+
+/**
+ * Tap on encoder updates using the encoder keymap
+ */
+void encoder_update_kb(uint8_t index, bool clockwise) {
+    int layer = get_highest_layer(layer_state);
+
+    uint16_t code;
+    do {
+        code = pgm_read_word(&encoder_keymaps[layer--][index][clockwise]);
+    } while (code == KC_TRNS);
+
+    tap_code16(code);
+}
+
+static bool encoder_read_state(uint8_t *state) {
+    uint8_t           mcp23018_pin_state;
+    mcp23018_status_t status = mcp23018_readReg(GPIOB, &mcp23018_pin_state, 1);
+    if (status == 0) {
+        *state = (mcp23018_pin_state & 0b110000) >> 4;
+        return true;
+    }
+    return false;
+}
+
+static void encoder_update(int8_t index, uint8_t state) {
+    encoder_pulses += encoder_LUT[state & 0xF];
+    if (encoder_pulses >= ENCODER_RESOLUTION) {
+        encoder_update_kb(index, ENCODER_CLOCKWISE);
+    }
+    if (encoder_pulses <= -ENCODER_RESOLUTION) {  // direction is arbitrary here, but this clockwise
+        encoder_update_kb(index, ENCODER_COUNTER_CLOCKWISE);
+    }
+    encoder_pulses %= ENCODER_RESOLUTION;
+}
+
+/**
+ * Read the secondary encoder over i2c
+ */
+void secondary_encoder_read(void) {
+    uint8_t state;
+    if (encoder_read_state(&state)) {
+        encoder_state <<= 2;
+        encoder_state |= state;
+        encoder_update(1, encoder_state);
+    }
+}
+
+/**
+ * Initialize the secondary encoder over i2c
+ */
+void secondary_encoder_init(void) { encoder_read_state(&encoder_state); }