diff --git a/app/src/split/CMakeLists.txt b/app/src/split/CMakeLists.txt
index 27abb82ad06..d4b673571b9 100644
--- a/app/src/split/CMakeLists.txt
+++ b/app/src/split/CMakeLists.txt
@@ -3,4 +3,8 @@
 
 if (CONFIG_ZMK_SPLIT_BLE)
     add_subdirectory(bluetooth)
-endif()
\ No newline at end of file
+endif()
+
+if (CONFIG_ZMK_SPLIT_SERIAL)
+    add_subdirectory(serial)
+endif()
diff --git a/app/src/split/Kconfig b/app/src/split/Kconfig
index dbe5f092644..187d41998e8 100644
--- a/app/src/split/Kconfig
+++ b/app/src/split/Kconfig
@@ -18,9 +18,13 @@ config ZMK_SPLIT_BLE
     select BT_USER_PHY_UPDATE
     select BT_AUTO_PHY_UPDATE
 
+config ZMK_SPLIT_SERIAL
+    bool "Serial"
+
 endchoice
 
 #ZMK_SPLIT
 endif
 
 rsource "bluetooth/Kconfig"
+rsource "serial/Kconfig"
diff --git a/app/src/split/serial/CMakeLists.txt b/app/src/split/serial/CMakeLists.txt
new file mode 100644
index 00000000000..42f9c956cb3
--- /dev/null
+++ b/app/src/split/serial/CMakeLists.txt
@@ -0,0 +1,13 @@
+# Copyright (c) 2022 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+target_link_libraries(app PRIVATE
+    COBS
+)
+
+if (CONFIG_ZMK_SPLIT_ROLE_CENTRAL)
+  target_sources(app PRIVATE central.c)
+  target_sources(app PRIVATE interrupt.c)
+else ()
+  target_sources(app PRIVATE peripheral.c)
+  target_sources(app PRIVATE polling.c)
+endif()
diff --git a/app/src/split/serial/Kconfig b/app/src/split/serial/Kconfig
new file mode 100644
index 00000000000..f2ccdf65157
--- /dev/null
+++ b/app/src/split/serial/Kconfig
@@ -0,0 +1,44 @@
+# Copyright (c) 2022 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+if ZMK_SPLIT && ZMK_SPLIT_SERIAL
+
+menu "Serial Transport"
+
+if ZMK_SPLIT_ROLE_CENTRAL
+
+config ZMK_SPLIT_SERIAL_CENTRAL_PRIORITY
+    int "Serial split peripheral workqueue thread priority"
+    default 5
+
+config ZMK_SPLIT_SERIAL_CENTRAL_POSITION_QUEUE_SIZE
+    int "Max number of key position state events to queue when received from peripherals"
+    default 5
+
+config ZMK_SPLIT_SERIAL_CENTRAL_RUN_STACK_SIZE
+    int "Serial split central write thread stack size"
+    default 512
+
+endif # ZMK_SPLIT_ROLE_CENTRAL
+
+if !ZMK_SPLIT_ROLE_CENTRAL
+
+config ZMK_SPLIT_SERIAL_PERIPHERAL_STACK_SIZE
+    int "Serial split peripheral notify thread stack size"
+    default 650
+
+config ZMK_SPLIT_SERIAL_PERIPHERAL_PRIORITY
+    int "Serial split peripheral notify thread priority"
+    default 5
+
+config ZMK_SPLIT_SERIAL_PERIPHERAL_POSITION_QUEUE_SIZE
+    int "Max number of key position state events to queue to send to the central"
+    default 10
+
+#!ZMK_SPLIT_ROLE_CENTRAL
+endif
+
+endmenu
+
+#ZMK_SPLIT_SERIAL
+endif
diff --git a/app/src/split/serial/central.c b/app/src/split/serial/central.c
new file mode 100644
index 00000000000..986c0992c6c
--- /dev/null
+++ b/app/src/split/serial/central.c
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <cobs.h>
+#include <zephyr/net/buf.h>
+#include <zephyr/sys/crc.h>
+#include <zmk/event_manager.h>
+#include <zmk/events/position_state_changed.h>
+#include <zmk/events/sensor_event.h>
+#include <zmk/sensors.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#include "private.h"
+
+/* Let's provide enough space for multiple messages to reduce the risk of
+ * having to drop new ones. */
+RING_BUF_DECLARE(zmk_split_serial_rx_ringbuf, MAX_MESSAGE_LEN * 2);
+
+static void on_rx_done(struct net_buf_simple *const buf) {
+    static uint8_t positions[POSITION_STATE_DATA_LEN];
+    const int64_t timestamp = k_uptime_get();
+
+    if (buf->len < 3) {
+        LOG_ERR("Message is smaller than it's header");
+        return;
+    }
+
+    const uint16_t crc_received = net_buf_simple_remove_le16(buf);
+    const uint16_t crc_calculated = crc16_ccitt(0, buf->data, buf->len);
+    if (crc_received != crc_calculated) {
+        LOG_ERR("Invalid checksum. received=%04X calculated=%04x", crc_received, crc_calculated);
+        return;
+    }
+
+    const uint8_t event_type = net_buf_simple_pull_u8(buf);
+    switch (event_type) {
+    case SPLIT_EVENT_POSITION: {
+        const uint8_t *const new_positions = buf->data;
+        const size_t new_positions_len = buf->len;
+
+        if (new_positions_len > ARRAY_SIZE(positions)) {
+            LOG_ERR("Got %zu positions but we only support %zu", new_positions_len,
+                    ARRAY_SIZE(positions));
+            return;
+        }
+
+        for (size_t positions_index = 0; positions_index < new_positions_len;
+             positions_index += 1) {
+
+            const uint8_t state = new_positions[positions_index];
+            const uint8_t changed = state ^ positions[positions_index];
+            positions[positions_index] = state;
+
+            for (size_t bit_index = 0; bit_index < 8; bit_index += 1) {
+                if (changed & BIT(bit_index)) {
+                    const struct zmk_position_state_changed ev = {
+                        .source = 0,
+                        .position = positions_index * 8 + bit_index,
+                        .state = state & BIT(bit_index),
+                        .timestamp = timestamp,
+                    };
+                    LOG_DBG("Trigger key position state change for %d", ev.position);
+
+                    ZMK_EVENT_RAISE(new_zmk_position_state_changed(ev));
+                }
+            }
+        }
+        break;
+    }
+    default:
+        LOG_ERR("Unsupported event type: %02X", event_type);
+        break;
+    }
+}
+
+static void rx_work_handler(struct k_work *work) {
+    ARG_UNUSED(work);
+
+    NET_BUF_SIMPLE_DEFINE_STATIC(rx_buf, MAX_MESSAGE_LEN);
+    static struct cobs_decode cobs_decode;
+
+    for (;;) {
+        uint8_t encoded_byte;
+        const size_t num_read =
+            ring_buf_get(&zmk_split_serial_rx_ringbuf, &encoded_byte, sizeof(encoded_byte));
+        if (num_read == 0) {
+            /* No data, we're done here. */
+            return;
+        }
+        __ASSERT_NO_MSG(num_read == 1);
+
+        uint8_t decoded_byte = 0x00;
+        bool decoded_byte_available = false;
+        enum cobs_decode_result decode_result =
+            cobs_decode_stream(&cobs_decode, encoded_byte, &decoded_byte, &decoded_byte_available);
+
+        if (decoded_byte_available) {
+            if (net_buf_simple_tailroom(&rx_buf) == 0) {
+                LOG_DBG("message is too big");
+                net_buf_simple_reset(&rx_buf);
+                cobs_decode_reset(&cobs_decode);
+                continue;
+            }
+
+            net_buf_simple_add_u8(&rx_buf, decoded_byte);
+        }
+
+        switch (decode_result) {
+        case COBS_DECODE_RESULT_CONSUMED:
+            break;
+
+        case COBS_DECODE_RESULT_FINISHED: {
+            cobs_decode_reset(&cobs_decode);
+            on_rx_done(&rx_buf);
+            net_buf_simple_reset(&rx_buf);
+            break;
+        }
+
+        case COBS_DECODE_RESULT_UNEXPECTED_ZERO:
+            LOG_DBG("unexpected zero in COBS data");
+            net_buf_simple_reset(&rx_buf);
+            cobs_decode_reset(&cobs_decode);
+            break;
+
+        case COBS_DECODE_RESULT_ERROR:
+            LOG_DBG("COBS error");
+            net_buf_simple_reset(&rx_buf);
+            cobs_decode_reset(&cobs_decode);
+            break;
+        }
+    }
+}
+K_WORK_DEFINE(zmk_split_serial_rx_work, rx_work_handler);
diff --git a/app/src/split/serial/interrupt.c b/app/src/split/serial/interrupt.c
new file mode 100644
index 00000000000..5872bf36d5e
--- /dev/null
+++ b/app/src/split/serial/interrupt.c
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/uart.h>
+#include <zephyr/sys/ring_buffer.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#include "private.h"
+
+static const struct device *const uart_dev = DEVICE_DT_GET(DT_CHOSEN(zmk_split_serial));
+
+static void clear_fifo(const struct device *const dev) {
+    uint8_t c;
+    while (uart_fifo_read(dev, &c, 1) > 0) {
+    }
+}
+
+/**
+ * Read from the FIFO until it returns a size of 0.
+ *
+ * This is a workaround because some drivers read max 1 character per call.
+ */
+static int uart_fifo_read_all(const struct device *dev, uint8_t *rx_data, int size) {
+    int ret;
+    int num_read = 0;
+
+    while (size > 0) {
+        ret = uart_fifo_read(dev, rx_data, size);
+        if (ret < 0) {
+            LOG_ERR("Failed to read fifo: %d", ret);
+            return ret;
+        }
+        if (ret == 0) {
+            break;
+        }
+
+        __ASSERT_NO_MSG(num_read <= size);
+
+        rx_data += ret;
+        size -= ret;
+        num_read += ret;
+    }
+
+    return num_read;
+}
+
+static void irq_rx_callback(const struct device *const dev) {
+    int ret;
+    bool had_data = false;
+
+    for (;;) {
+        uint8_t *data = NULL;
+        const uint32_t max_size =
+            ring_buf_put_claim(&zmk_split_serial_rx_ringbuf, &data, UINT32_MAX);
+        if (max_size == 0) {
+            clear_fifo(uart_dev);
+            break;
+        }
+        const int max_size_int = MIN(max_size, INT_MAX);
+
+        uint32_t num_read;
+        ret = uart_fifo_read_all(dev, data, max_size_int);
+        if (ret < 0) {
+            LOG_ERR("Failed to read fifo: %d", ret);
+            num_read = 0;
+        } else {
+            num_read = ret;
+            had_data = true;
+        }
+
+        ret = ring_buf_put_finish(&zmk_split_serial_rx_ringbuf, num_read);
+        __ASSERT_NO_MSG(ret == 0);
+
+        if (num_read < max_size_int) {
+            break;
+        }
+
+        /* There's may still be data in the FIFO, if:
+         * - The ring buffer didn't return it's full capacity because
+         *   it's about to wrap. Another attempt will return the rest.
+         * - In between claim and finish, data was read from the ring
+         *   buffer so another attempt will return more data.
+         * - The ring buffer is still full. Another attempt will stop
+         *   the loop.
+         */
+    }
+
+    if (had_data) {
+        k_work_submit(&zmk_split_serial_rx_work);
+    }
+}
+
+static void irq_callback(const struct device *const dev, void *const user_data) {
+    ARG_UNUSED(dev);
+
+    if (!uart_irq_update(dev)) {
+        return;
+    }
+
+    if (uart_irq_rx_ready(dev)) {
+        irq_rx_callback(dev);
+    }
+}
+
+static int init(const struct device *dev) {
+    ARG_UNUSED(dev);
+
+    if (!device_is_ready(uart_dev)) {
+        LOG_ERR("split uart device is not ready");
+        return -EAGAIN;
+    }
+
+    uart_irq_rx_disable(uart_dev);
+    uart_irq_tx_disable(uart_dev);
+    clear_fifo(uart_dev);
+
+    uart_irq_callback_user_data_set(uart_dev, irq_callback, NULL);
+    uart_irq_rx_enable(uart_dev);
+
+    return 0;
+}
+SYS_INIT(init, APPLICATION, CONFIG_APPLICATION_INIT_PRIORITY);
diff --git a/app/src/split/serial/peripheral.c b/app/src/split/serial/peripheral.c
new file mode 100644
index 00000000000..9fc3929edce
--- /dev/null
+++ b/app/src/split/serial/peripheral.c
@@ -0,0 +1,170 @@
+/*
+ * Copyright (c) 2022 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <cobs.h>
+#include <drivers/behavior.h>
+#include <zephyr/device.h>
+#include <zephyr/drivers/sensor.h>
+#include <zephyr/init.h>
+#include <zephyr/sys/crc.h>
+#include <zmk/behavior.h>
+#include <zmk/event_manager.h>
+#include <zmk/events/position_state_changed.h>
+#include <zmk/events/sensor_event.h>
+#include <zmk/events/split_peripheral_status_changed.h>
+#include <zmk/matrix.h>
+#include <zmk/sensors.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#include "private.h"
+
+K_THREAD_STACK_DEFINE(service_q_stack, CONFIG_ZMK_SPLIT_SERIAL_PERIPHERAL_STACK_SIZE);
+static struct k_work_q service_work_q;
+
+static uint8_t position_state[POSITION_STATE_DATA_LEN];
+K_MSGQ_DEFINE(position_state_msgq, sizeof(position_state),
+              CONFIG_ZMK_SPLIT_SERIAL_PERIPHERAL_POSITION_QUEUE_SIZE, 4);
+NET_BUF_SIMPLE_DEFINE_STATIC(message_buf, MAX_MESSAGE_LEN);
+static uint8_t tx_buf[COBS_MAX_ENCODED_SIZE(MAX_MESSAGE_LEN) + 1];
+
+static void send_position_handler(struct k_work *work) {
+    ARG_UNUSED(work);
+
+    uint8_t state[sizeof(position_state)];
+    while (k_msgq_get(&position_state_msgq, &state, K_NO_WAIT) == 0) {
+        LOG_INF("send position");
+
+        net_buf_simple_reset(&message_buf);
+        net_buf_simple_add_u8(&message_buf, SPLIT_EVENT_POSITION);
+        net_buf_simple_add_mem(&message_buf, state, sizeof(state));
+
+        const uint16_t crc = crc16_ccitt(0, message_buf.data, message_buf.len);
+        net_buf_simple_add_le16(&message_buf, crc);
+
+        const size_t encoded_length = cobs_encode(message_buf.data, message_buf.len, tx_buf);
+        tx_buf[encoded_length] = 0x00;
+        zmk_split_serial_send(tx_buf, encoded_length + 1);
+    }
+};
+K_WORK_DEFINE(send_position_work, send_position_handler);
+
+static int queue_sending_position_state(void) {
+    int err = k_msgq_put(&position_state_msgq, position_state, K_MSEC(100));
+    if (err) {
+        switch (err) {
+        case -EAGAIN: {
+            LOG_WRN("Position state message queue full, popping first message and queueing again");
+            uint8_t discarded_state[sizeof(position_state)];
+            k_msgq_get(&position_state_msgq, &discarded_state, K_NO_WAIT);
+            return queue_sending_position_state();
+        }
+        default:
+            LOG_WRN("Failed to queue position state to send (%d)", err);
+            return err;
+        }
+    }
+
+    k_work_submit_to_queue(&service_work_q, &send_position_work);
+
+    return 0;
+}
+
+static int position_pressed(const uint8_t position) {
+    WRITE_BIT(position_state[position / 8], position % 8, true);
+    return queue_sending_position_state();
+}
+
+static int position_released(const uint8_t position) {
+    WRITE_BIT(position_state[position / 8], position % 8, false);
+    return queue_sending_position_state();
+}
+
+#if ZMK_KEYMAP_HAS_SENSORS
+K_MSGQ_DEFINE(sensor_state_msgq, sizeof(struct sensor_event),
+              CONFIG_ZMK_SPLIT_SERIAL_PERIPHERAL_POSITION_QUEUE_SIZE, 4);
+
+static void send_sensor_state_callback(struct k_work *work) {
+    while (k_msgq_get(&sensor_state_msgq, &last_sensor_event, K_NO_WAIT) == 0) {
+        LOG_INF("send sensor state");
+        // TODO
+    }
+};
+K_WORK_DEFINE(service_sensor_notify_work, send_sensor_state_callback);
+
+static int send_sensor_state(struct sensor_event ev) {
+    int err = k_msgq_put(&sensor_state_msgq, &ev, K_MSEC(100));
+    if (err) {
+        // retry...
+        switch (err) {
+        case -EAGAIN: {
+            LOG_WRN("Sensor state message queue full, popping first message and queueing again");
+            struct sensor_event discarded_state;
+            k_msgq_get(&sensor_state_msgq, &discarded_state, K_NO_WAIT);
+            return send_sensor_state(ev);
+        }
+        default:
+            LOG_WRN("Failed to queue sensor state to send (%d)", err);
+            return err;
+        }
+    }
+
+    k_work_submit_to_queue(&service_work_q, &service_sensor_notify_work);
+    return 0;
+}
+
+static int sensor_triggered(uint8_t sensor_index,
+                            const struct zmk_sensor_channel_data channel_data[],
+                            size_t channel_data_size) {
+    if (channel_data_size > ZMK_SENSOR_EVENT_MAX_CHANNELS) {
+        return -EINVAL;
+    }
+
+    struct sensor_event ev =
+        (struct sensor_event){.sensor_index = sensor_index, .channel_data_size = channel_data_size};
+    memcpy(ev.channel_data, channel_data,
+           channel_data_size * sizeof(struct zmk_sensor_channel_data));
+    return send_sensor_state(ev);
+}
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
+
+static int split_listener(const zmk_event_t *eh) {
+    LOG_DBG("");
+    const struct zmk_position_state_changed *pos_ev;
+    if ((pos_ev = as_zmk_position_state_changed(eh)) != NULL) {
+        if (pos_ev->state) {
+            return position_pressed(pos_ev->position);
+        } else {
+            return position_released(pos_ev->position);
+        }
+    }
+
+#if ZMK_KEYMAP_HAS_SENSORS
+    const struct zmk_sensor_event *sensor_ev;
+    if ((sensor_ev = as_zmk_sensor_event(eh)) != NULL) {
+        return sensor_triggered(sensor_ev->sensor_index, sensor_ev->channel_data,
+                                sensor_ev->channel_data_size);
+    }
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
+
+    return ZMK_EV_EVENT_BUBBLE;
+}
+ZMK_LISTENER(split_listener, split_listener);
+ZMK_SUBSCRIPTION(split_listener, zmk_position_state_changed);
+#if ZMK_KEYMAP_HAS_SENSORS
+ZMK_SUBSCRIPTION(split_listener, zmk_sensor_event);
+#endif /* ZMK_KEYMAP_HAS_SENSORS */
+
+static int init(const struct device *_arg) {
+    static const struct k_work_queue_config queue_config = {
+        .name = "Split Peripheral Notification Queue"};
+    k_work_queue_start(&service_work_q, service_q_stack, K_THREAD_STACK_SIZEOF(service_q_stack),
+                       CONFIG_ZMK_SPLIT_SERIAL_PERIPHERAL_PRIORITY, &queue_config);
+
+    return 0;
+}
+SYS_INIT(init, APPLICATION, CONFIG_APPLICATION_INIT_PRIORITY);
diff --git a/app/src/split/serial/polling.c b/app/src/split/serial/polling.c
new file mode 100644
index 00000000000..08ccc99ebf0
--- /dev/null
+++ b/app/src/split/serial/polling.c
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/uart.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#include "private.h"
+
+static const struct device *const uart_dev = DEVICE_DT_GET(DT_CHOSEN(zmk_split_serial));
+
+void zmk_split_serial_send(const void *const data_, const size_t length) {
+    const uint8_t *const data = data_;
+    for (size_t position = 0; position < length; position += 1) {
+        uart_poll_out(uart_dev, data[position]);
+    }
+}
+
+static int init(const struct device *dev) {
+    ARG_UNUSED(dev);
+
+    if (!device_is_ready(uart_dev)) {
+        LOG_ERR("split uart device is not ready");
+        return -EAGAIN;
+    }
+
+    return 0;
+}
+SYS_INIT(init, APPLICATION, CONFIG_APPLICATION_INIT_PRIORITY);
diff --git a/app/src/split/serial/private.h b/app/src/split/serial/private.h
new file mode 100644
index 00000000000..230857c17d7
--- /dev/null
+++ b/app/src/split/serial/private.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#ifndef PRIVATE_H
+#define PRIVATE_H
+
+#include <zephyr/sys/ring_buffer.h>
+#include <zmk/events/sensor_event.h>
+#include <zmk/sensors.h>
+
+#define POSITION_STATE_DATA_LEN 16
+/* event_type, event_payload, CRC16 */
+#define MAX_MESSAGE_LEN                                                                            \
+    (sizeof(uint8_t) + MAX(POSITION_STATE_DATA_LEN, sizeof(struct sensor_event)) + sizeof(uint16_t))
+
+#define SPLIT_EVENT_POSITION 0
+#define SPLIT_EVENT_SENSOR 1
+
+struct sensor_event {
+    uint8_t sensor_index;
+
+    uint8_t channel_data_size;
+    struct zmk_sensor_channel_data channel_data[ZMK_SENSOR_EVENT_MAX_CHANNELS];
+} __packed;
+
+#ifdef CONFIG_ZMK_SPLIT_ROLE_CENTRAL
+extern struct ring_buf zmk_split_serial_rx_ringbuf;
+extern struct k_work zmk_split_serial_rx_work;
+#else
+void zmk_split_serial_send(const void *const data, const size_t length);
+#endif
+
+#endif /* PRIVATE_H */
diff --git a/app/west.yml b/app/west.yml
index ffa36ca36e9..92a9787468f 100644
--- a/app/west.yml
+++ b/app/west.yml
@@ -4,6 +4,9 @@ manifest:
       url-base: https://github.com/zephyrproject-rtos
     - name: zmkfirmware
       url-base: https://github.com/zmkfirmware
+    - name: grandcentrix
+      url-base: https://github.com/grandcentrix
+
   projects:
     - name: zephyr
       remote: zmkfirmware
@@ -30,5 +33,11 @@ manifest:
           - edtt
           - trusted-firmware-m
           - sof
+    - name: cobs
+      repo-path: cobs
+      remote: grandcentrix
+      revision: 0876ef80209618b10508af728731f4944f9d2fd2
+      path: modules/lib/cobs
+
   self:
     west-commands: scripts/west-commands.yml