diff --git a/nimble/transport/pkg.yml b/nimble/transport/pkg.yml
index 5070c72883..30237f75bd 100644
--- a/nimble/transport/pkg.yml
+++ b/nimble/transport/pkg.yml
@@ -48,6 +48,8 @@ pkg.deps.'BLE_TRANSPORT_HS == "cdc"':
     - nimble/transport/cdc
 pkg.deps.'BLE_TRANSPORT_LL == "apollo3"':
     - nimble/transport/apollo3
+pkg.deps.'BLE_TRANSPORT_LL == "uart_ll"':
+    - nimble/transport/uart_ll
 
 pkg.deps.BLE_MONITOR_RTT:
     - "@apache-mynewt-core/hw/drivers/rtt"
diff --git a/nimble/transport/syscfg.yml b/nimble/transport/syscfg.yml
index 7f02f6cc8f..febe09d401 100644
--- a/nimble/transport/syscfg.yml
+++ b/nimble/transport/syscfg.yml
@@ -46,6 +46,7 @@ syscfg.defs:
             - nrf5340
             - socket
             - apollo3
+            - uart_ll
             - custom
 
     BLE_TRANSPORT_ACL_COUNT:
diff --git a/nimble/transport/uart_ll/pkg.yml b/nimble/transport/uart_ll/pkg.yml
new file mode 100644
index 0000000000..efc97d5456
--- /dev/null
+++ b/nimble/transport/uart_ll/pkg.yml
@@ -0,0 +1,32 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+pkg.name: nimble/transport/uart_ll
+pkg.description: HCI H4 transport over UART to external controller
+pkg.author: "Apache Mynewt <dev@mynewt.apache.org>"
+pkg.homepage: "https://mynewt.apache.org/"
+
+pkg.deps:
+    - "@apache-mynewt-core/hw/hal"
+    - "@apache-mynewt-core/kernel/os"
+    - nimble
+    - nimble/transport/common/hci_h4
+
+pkg.apis:
+    - ble_transport
diff --git a/nimble/transport/uart_ll/src/hci_uart.c b/nimble/transport/uart_ll/src/hci_uart.c
new file mode 100644
index 0000000000..95eae3f4b3
--- /dev/null
+++ b/nimble/transport/uart_ll/src/hci_uart.c
@@ -0,0 +1,245 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#include <assert.h>
+#include <string.h>
+#include <errno.h>
+#include <stdint.h>
+#include <sysinit/sysinit.h>
+#include <syscfg/syscfg.h>
+#include "os/os_mbuf.h"
+#include "os/os_mempool.h"
+#include "hal/hal_uart.h"
+#include "nimble/transport.h"
+#include "nimble/transport/hci_h4.h"
+
+#define TX_Q_SIZE   (MYNEWT_VAL(BLE_TRANSPORT_ACL_FROM_HS_COUNT) + 1)
+
+struct hci_uart_tx {
+    uint8_t type;
+    uint8_t sent_type;
+    uint16_t len;
+    uint16_t idx;
+
+    struct os_mbuf *om;
+    uint8_t *buf;
+
+    STAILQ_ENTRY(hci_uart_tx) tx_q_next;
+};
+
+static STAILQ_HEAD(, hci_uart_tx) tx_q;
+
+static struct os_mempool pool_tx_q;
+static uint8_t pool_tx_q_buf[ OS_MEMPOOL_BYTES(TX_Q_SIZE,
+                                               sizeof(struct hci_uart_tx)) ];
+
+struct hci_h4_sm hci_uart_h4sm;
+
+static int
+hci_uart_frame_cb(uint8_t pkt_type, void *data)
+{
+    switch (pkt_type) {
+    case HCI_H4_EVT:
+        return ble_transport_to_hs_evt(data);
+    case HCI_H4_ACL:
+        return ble_transport_to_hs_acl(data);
+    default:
+        assert(0);
+        break;
+    }
+
+    return -1;
+}
+
+static int
+hci_uart_rx_char(void *arg, uint8_t data)
+{
+    hci_h4_sm_rx(&hci_uart_h4sm, &data, 1);
+
+    return 0;
+}
+
+static int
+hci_uart_tx_char(void *arg)
+{
+    struct hci_uart_tx *tx;
+    uint8_t ch;
+    os_sr_t sr;
+
+    OS_ENTER_CRITICAL(sr);
+    tx = STAILQ_FIRST(&tx_q);
+    OS_EXIT_CRITICAL(sr);
+    if (!tx) {
+        return -1;
+    }
+
+    if (!tx->sent_type) {
+        tx->sent_type = 1;
+        return tx->type;
+    }
+
+    switch (tx->type) {
+    case HCI_H4_CMD:
+        ch = tx->buf[tx->idx];
+        tx->idx++;
+        if (tx->idx == tx->len) {
+            ble_transport_free(tx->buf);
+            OS_ENTER_CRITICAL(sr);
+            STAILQ_REMOVE_HEAD(&tx_q, tx_q_next);
+            OS_EXIT_CRITICAL(sr);
+            os_memblock_put(&pool_tx_q, tx);
+        }
+        break;
+    case HCI_H4_ACL:
+        os_mbuf_copydata(tx->om, 0, 1, &ch);
+        os_mbuf_adj(tx->om, 1);
+        tx->len--;
+        if (tx->len == 0) {
+            os_mbuf_free_chain(tx->om);
+            OS_ENTER_CRITICAL(sr);
+            STAILQ_REMOVE_HEAD(&tx_q, tx_q_next);
+            OS_EXIT_CRITICAL(sr);
+            os_memblock_put(&pool_tx_q, tx);
+        }
+        break;
+    default:
+        assert(0);
+        OS_ENTER_CRITICAL(sr);
+        STAILQ_REMOVE_HEAD(&tx_q, tx_q_next);
+        OS_EXIT_CRITICAL(sr);
+        os_memblock_put(&pool_tx_q, tx);
+    }
+
+    return ch;
+}
+
+static int
+hci_uart_configure(void)
+{
+    enum hal_uart_parity parity;
+    enum hal_uart_flow_ctl flowctl;
+    int rc;
+
+    rc = hal_uart_init_cbs(MYNEWT_VAL(BLE_TRANSPORT_UART_PORT),
+                           hci_uart_tx_char, NULL,
+                           hci_uart_rx_char, NULL);
+    if (rc != 0) {
+        return -1;
+    }
+
+    if (MYNEWT_VAL_CHOICE(BLE_TRANSPORT_UART_PARITY, odd)) {
+        parity = HAL_UART_PARITY_ODD;
+    } else if (MYNEWT_VAL_CHOICE(BLE_TRANSPORT_UART_PARITY, even)) {
+        parity = HAL_UART_PARITY_EVEN;
+    } else {
+        parity = HAL_UART_PARITY_NONE;
+    }
+
+    if (MYNEWT_VAL_CHOICE(BLE_TRANSPORT_UART_FLOW_CONTROL, rtscts)) {
+        flowctl = HAL_UART_FLOW_CTL_RTS_CTS;
+    } else {
+        flowctl = HAL_UART_FLOW_CTL_NONE;
+    }
+
+    rc = hal_uart_config(MYNEWT_VAL(BLE_TRANSPORT_UART_PORT),
+                         MYNEWT_VAL(BLE_TRANSPORT_UART_BAUDRATE),
+                         MYNEWT_VAL(BLE_TRANSPORT_UART_DATA_BITS),
+                         MYNEWT_VAL(BLE_TRANSPORT_UART_STOP_BITS),
+                         parity, flowctl);
+    if (rc != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+int
+ble_transport_to_ll_cmd_impl(void *buf)
+{
+    struct hci_uart_tx *txe;
+    os_sr_t sr;
+
+    txe = os_memblock_get(&pool_tx_q);
+    if (!txe) {
+        assert(0);
+        return -ENOMEM;
+    }
+
+    txe->type = HCI_H4_CMD;
+    txe->sent_type = 0;
+    txe->len = 3 + ((uint8_t *)buf)[2];
+    txe->buf = buf;
+    txe->idx = 0;
+    txe->om = NULL;
+
+    OS_ENTER_CRITICAL(sr);
+    STAILQ_INSERT_TAIL(&tx_q, txe, tx_q_next);
+    OS_EXIT_CRITICAL(sr);
+
+    hal_uart_start_tx(MYNEWT_VAL(BLE_TRANSPORT_UART_PORT));
+
+    return 0;
+}
+
+int
+ble_transport_to_ll_acl_impl(struct os_mbuf *om)
+{
+    struct hci_uart_tx *txe;
+    os_sr_t sr;
+
+    txe = os_memblock_get(&pool_tx_q);
+    if (!txe) {
+        assert(0);
+        return -ENOMEM;
+    }
+
+    txe->type = HCI_H4_ACL;
+    txe->sent_type = 0;
+    txe->len = OS_MBUF_PKTLEN(om);
+    txe->idx = 0;
+    txe->buf = NULL;
+    txe->om = om;
+
+    OS_ENTER_CRITICAL(sr);
+    STAILQ_INSERT_TAIL(&tx_q, txe, tx_q_next);
+    OS_EXIT_CRITICAL(sr);
+
+    hal_uart_start_tx(MYNEWT_VAL(BLE_TRANSPORT_UART_PORT));
+
+    return 0;
+}
+
+void
+ble_transport_ll_init(void)
+{
+    int rc;
+
+    SYSINIT_ASSERT_ACTIVE();
+
+    rc = hci_uart_configure();
+    SYSINIT_PANIC_ASSERT(rc == 0);
+
+    rc = os_mempool_init(&pool_tx_q, TX_Q_SIZE, sizeof(struct hci_uart_tx),
+                         pool_tx_q_buf, "hci_uart_tx_q");
+    SYSINIT_PANIC_ASSERT(rc == 0);
+
+    hci_h4_sm_init(&hci_uart_h4sm, &hci_h4_allocs_from_ll, hci_uart_frame_cb);
+
+    STAILQ_INIT(&tx_q);
+}
diff --git a/nimble/transport/uart_ll/syscfg.yml b/nimble/transport/uart_ll/syscfg.yml
new file mode 100644
index 0000000000..ccf38b61a5
--- /dev/null
+++ b/nimble/transport/uart_ll/syscfg.yml
@@ -0,0 +1,39 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+syscfg.defs:
+    BLE_TRANSPORT_UART_LL_PORT:
+        description: UART index to use for HCI interface
+        value: 0
+    BLE_TRANSPORT_UART_LL_BAUDRATE:
+        description: Baudrate on UART
+        value: 1000000
+    BLE_TRANSPORT_UART_LL_DATA_BITS:
+        description: Number of data bits on UART
+        value: 8
+    BLE_TRANSPORT_UART_LL_STOP_BITS:
+        description: Number of stop bits on UART
+        value: 1
+    BLE_TRANSPORT_UART_LL_PARITY:
+        description: Parity on UART
+        value: none
+        choices: none,even,odd
+    BLE_TRANSPORT_UART_LL_FLOW_CONTROL:
+        description: Flow control on UART
+        choices: off,rtscts
+        value: rtscts