extmod/modbluetooth: Allow config of scan interval/window.

This adds two additional optional kwargs to `gap_scan()`:
  - `interval_us`: How long between scans.
  - `window_us`: How long to scan for during a scan.

The default with NimBLE is a 11.25ms window with a 1.28s interval.

Changing these parameters is important for detecting low-frequency
advertisements (e.g. beacons).

Note: these params are in microseconds, not milliseconds in order
to allow the 625us granularity offered by the spec.

1 files changed, 5 insertions, 5 deletions

diff --git a/extmod/modbluetooth_nimble.c b/extmod/modbluetooth_nimble.c
index 1e7211bfe..727894f86 100644
--- a/extmod/modbluetooth_nimble.c
+++ b/extmod/modbluetooth_nimble.c
@@ -614,16 +614,16 @@ STATIC int gap_scan_cb(struct ble_gap_event *event, void *arg) {
     return 0;
 }
 
-int mp_bluetooth_gap_scan_start(int32_t duration_ms) {
+int mp_bluetooth_gap_scan_start(int32_t duration_ms, int32_t interval_us, int32_t window_us) {
     if (duration_ms == 0) {
         duration_ms = BLE_HS_FOREVER;
     }
-    STATIC const struct ble_gap_disc_params discover_params = {
-        .itvl = BLE_GAP_SCAN_SLOW_INTERVAL1,
-        .window = BLE_GAP_SCAN_SLOW_WINDOW1,
+    struct ble_gap_disc_params discover_params = {
+        .itvl = MAX(BLE_HCI_SCAN_ITVL_MIN, MIN(BLE_HCI_SCAN_ITVL_MAX, interval_us / BLE_HCI_SCAN_ITVL)),
+        .window = MAX(BLE_HCI_SCAN_WINDOW_MIN, MIN(BLE_HCI_SCAN_WINDOW_MAX, window_us / BLE_HCI_SCAN_ITVL)),
         .filter_policy = BLE_HCI_CONN_FILT_NO_WL,
         .limited = 0,
-        .passive = 0,
+        .passive = 1,  // TODO: Handle BLE_HCI_ADV_RPT_EVTYPE_SCAN_RSP in gap_scan_cb above.
         .filter_duplicates = 0,
     };
     int err = ble_gap_disc(BLE_OWN_ADDR_PUBLIC, duration_ms, &discover_params, gap_scan_cb, NULL);