drv/bluetooth: handle remote + observing

If observing has already started when connecting to another Bluetooth
device, we need to pause observing (which is passive scanning) so that
we can do active scanning to find the device we want to connect to.
Then we need to restore passive scanning for observing once active
scanning is complete.

This is done on CC2540 and BTStack. On BlueNRG, the chip can't handle
observing while being connected to another device so we just raise
an error instead.

Author: dlech

lib/pbio/drv/bluetooth/bluetooth_btstack.c

@@ -625,6 +625,11 @@ void pbdrv_bluetooth_set_notification_handler(pbdrv_bluetooth_receive_handler_t
     notification_handler = handler;
 }
 
+static void start_observing(void) {
+    gap_set_scan_params(0, 0x30, 0x30, 0);
+    gap_start_scan();
+}
+
 static PT_THREAD(scan_and_connect_task(struct pt *pt, pbio_task_t *task)) {
     pbdrv_bluetooth_scan_and_connect_context_t *context = task->context;
 
@@ -661,7 +666,7 @@ static PT_THREAD(scan_and_connect_task(struct pt *pt, pbio_task_t *task)) {
     memcpy(context->name, handset.name, sizeof(context->name));
 
     task->status = PBIO_SUCCESS;
-    PT_EXIT(pt);
+    goto out;
 
 cancel:
     if (handset.con_state == CON_STATE_WAIT_ADV_IND || handset.con_state == CON_STATE_WAIT_SCAN_RSP) {
@@ -673,6 +678,13 @@ static PT_THREAD(scan_and_connect_task(struct pt *pt, pbio_task_t *task)) {
     }
     handset.con_state = CON_STATE_NONE;
     task->status = PBIO_ERROR_CANCELED;
+
+out:
+    // restore observing state
+    if (is_observing) {
+        start_observing();
+    }
+
     PT_END(pt);
 }
 
@@ -760,8 +772,7 @@ void pbdrv_bluetooth_start_observing(pbio_task_t *task, pbdrv_bluetooth_start_ob
     observe_callback = callback;
 
     if (!is_observing) {
-        gap_set_scan_params(0, 0x30, 0x30, 0);
-        gap_start_scan();
+        start_observing();
         is_observing = true;
     }
 

lib/pbio/drv/bluetooth/bluetooth_stm32_bluenrg.c

@@ -416,6 +416,12 @@ static PT_THREAD(scan_and_connect_task(struct pt *pt, pbio_task_t *task)) {
 
     PT_BEGIN(pt);
 
+    // observing while connected to another device is not going to work
+    if (is_observing) {
+        task->status = PBIO_ERROR_INVALID_OP;
+        PT_EXIT(pt);
+    }
+
     // start scanning
     PT_WAIT_WHILE(pt, write_xfer_size);
     aci_gap_start_general_conn_establish_proc_begin(ACTIVE_SCAN, 0x0030, 0x0030, STATIC_RANDOM_ADDR, 0);

lib/pbio/drv/bluetooth/bluetooth_stm32_cc2640.c

@@ -474,6 +474,17 @@ static PT_THREAD(scan_and_connect_task(struct pt *pt, pbio_task_t *task)) {
 
     PT_BEGIN(pt);
 
+    // temporarily stop observing so we can active scan
+    if (is_observing) {
+        PT_WAIT_WHILE(pt, write_xfer_size);
+        GAP_DeviceDiscoveryCancel();
+        PT_WAIT_UNTIL(pt, hci_command_status);
+
+        if (read_buf[8] == bleSUCCESS) {
+            PT_WAIT_UNTIL(pt, device_discovery_done);
+        }
+    }
+
     // start scanning
 
     PT_WAIT_WHILE(pt, write_xfer_size);
@@ -484,7 +495,7 @@ static PT_THREAD(scan_and_connect_task(struct pt *pt, pbio_task_t *task)) {
 
     if (context->status != bleSUCCESS) {
         task->status = ble_error_to_pbio_error(context->status);
-        PT_EXIT(pt);
+        goto out;
     }
 
     device_discovery_done = false;
@@ -664,7 +675,7 @@ static PT_THREAD(scan_and_connect_task(struct pt *pt, pbio_task_t *task)) {
 
     task->status = PBIO_SUCCESS;
 
-    PT_EXIT(pt);
+    goto out;
 
 disconnect:
     PT_WAIT_WHILE(pt, write_xfer_size);
@@ -673,7 +684,7 @@ static PT_THREAD(scan_and_connect_task(struct pt *pt, pbio_task_t *task)) {
 
     // task->status must be set before goto disconnect!
 
-    PT_EXIT(pt);
+    goto out;
 
 cancel_connect:
     PT_WAIT_WHILE(pt, write_xfer_size);
@@ -691,6 +702,22 @@ static PT_THREAD(scan_and_connect_task(struct pt *pt, pbio_task_t *task)) {
 
 end_cancel:
     task->status = PBIO_ERROR_CANCELED;
+
+out:
+    // start passive scanning again if observing
+    if (is_observing) {
+        PT_WAIT_WHILE(pt, write_xfer_size);
+        GAP_DeviceDiscoveryRequest(GAP_DEVICE_DISCOVERY_MODE_NONDISCOVERABLE, 0, GAP_FILTER_POLICY_SCAN_ANY_CONNECT_ANY);
+        PT_WAIT_UNTIL(pt, hci_command_status);
+
+        if (read_buf[8] != bleSUCCESS) {
+            task->status = ble_error_to_pbio_error(read_buf[8]);
+            PT_EXIT(pt);
+        }
+
+        device_discovery_done = false;
+    }
+
     PT_END(pt);
 }