diff --git a/extmod/modbluetooth.c b/extmod/modbluetooth.c
index 0cfa3ac0d3..45ca61b6f0 100644
--- a/extmod/modbluetooth.c
+++ b/extmod/modbluetooth.c
@@ -301,9 +301,9 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_KW(bluetooth_ble_irq_obj, 1, bluetooth_ble_irq);
 // ----------------------------------------------------------------------------
 
 STATIC mp_obj_t bluetooth_ble_gap_advertise(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
-    enum { ARG_interval_ms, ARG_adv_data, ARG_resp_data, ARG_connectable };
+    enum { ARG_interval_us, ARG_adv_data, ARG_resp_data, ARG_connectable };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_interval_ms, MP_ARG_OBJ, {.u_obj = MP_OBJ_NEW_SMALL_INT(100)} },
+        { MP_QSTR_interval_us, MP_ARG_OBJ, {.u_obj = MP_OBJ_NEW_SMALL_INT(100)} },
         { MP_QSTR_adv_data, MP_ARG_OBJ, {.u_obj = mp_const_none } },
         { MP_QSTR_resp_data, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none } },
         { MP_QSTR_connectable, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_true } },
@@ -311,8 +311,8 @@ STATIC mp_obj_t bluetooth_ble_gap_advertise(size_t n_args, const mp_obj_t *pos_a
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    mp_int_t interval_ms;
-    if (args[ARG_interval_ms].u_obj == mp_const_none || (interval_ms = mp_obj_get_int(args[ARG_interval_ms].u_obj)) == 0) {
+    mp_int_t interval_us;
+    if (args[ARG_interval_us].u_obj == mp_const_none || (interval_us = mp_obj_get_int(args[ARG_interval_us].u_obj)) == 0) {
         mp_bluetooth_gap_advertise_stop();
         return mp_const_none;
     }
@@ -329,7 +329,7 @@ STATIC mp_obj_t bluetooth_ble_gap_advertise(size_t n_args, const mp_obj_t *pos_a
         mp_get_buffer_raise(args[ARG_resp_data].u_obj, &resp_bufinfo, MP_BUFFER_READ);
     }
 
-    return bluetooth_handle_errno(mp_bluetooth_gap_advertise_start(connectable, interval_ms, adv_bufinfo.buf, adv_bufinfo.len, resp_bufinfo.buf, resp_bufinfo.len));
+    return bluetooth_handle_errno(mp_bluetooth_gap_advertise_start(connectable, interval_us, adv_bufinfo.buf, adv_bufinfo.len, resp_bufinfo.buf, resp_bufinfo.len));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(bluetooth_ble_gap_advertise_obj, 1, bluetooth_ble_gap_advertise);
 
diff --git a/extmod/modbluetooth.h b/extmod/modbluetooth.h
index 8f34e3484d..f7284a43e8 100644
--- a/extmod/modbluetooth.h
+++ b/extmod/modbluetooth.h
@@ -157,7 +157,7 @@ void mp_bluetooth_get_device_addr(uint8_t *addr);
 
 // Start advertisement. Will re-start advertisement when already enabled.
 // Returns errno on failure.
-int mp_bluetooth_gap_advertise_start(bool connectable, uint16_t interval_ms, const uint8_t *adv_data, size_t adv_data_len, const uint8_t *sr_data, size_t sr_data_len);
+int mp_bluetooth_gap_advertise_start(bool connectable, int32_t interval_us, const uint8_t *adv_data, size_t adv_data_len, const uint8_t *sr_data, size_t sr_data_len);
 
 // Stop advertisement. No-op when already stopped.
 void mp_bluetooth_gap_advertise_stop(void);
diff --git a/extmod/modbluetooth_nimble.c b/extmod/modbluetooth_nimble.c
index 727894f862..8805d41007 100644
--- a/extmod/modbluetooth_nimble.c
+++ b/extmod/modbluetooth_nimble.c
@@ -341,7 +341,7 @@ void mp_bluetooth_get_device_addr(uint8_t *addr) {
     #endif
 }
 
-int mp_bluetooth_gap_advertise_start(bool connectable, uint16_t interval_ms, const uint8_t *adv_data, size_t adv_data_len, const uint8_t *sr_data, size_t sr_data_len) {
+int mp_bluetooth_gap_advertise_start(bool connectable, int32_t interval_us, const uint8_t *adv_data, size_t adv_data_len, const uint8_t *sr_data, size_t sr_data_len) {
     int ret;
 
     mp_bluetooth_gap_advertise_stop();
@@ -360,18 +360,12 @@ int mp_bluetooth_gap_advertise_start(bool connectable, uint16_t interval_ms, con
         }
     }
 
-    // Convert from 1ms to 0.625ms units.
-    interval_ms = interval_ms * 8 / 5;
-    if (interval_ms < 0x20 || interval_ms > 0x4000) {
-        return MP_EINVAL;
-    }
-
     struct ble_gap_adv_params adv_params = {
         .conn_mode = connectable ? BLE_GAP_CONN_MODE_UND : BLE_GAP_CONN_MODE_NON,
         .disc_mode = BLE_GAP_DISC_MODE_GEN,
-        .itvl_min = interval_ms,
-        .itvl_max = interval_ms,
-        .channel_map = 7, // all 3 channels
+        .itvl_min = interval_us / BLE_HCI_ADV_ITVL, // convert to 625us units.
+        .itvl_max = interval_us / BLE_HCI_ADV_ITVL,
+        .channel_map = 7, // all 3 channels.
     };
 
     ret = ble_gap_adv_start(BLE_OWN_ADDR_PUBLIC, NULL, BLE_HS_FOREVER, &adv_params, gap_event_cb, NULL);