Re: bluetoothctl: how to send notification/indcation from peripheral to central

Hi Luiz

Thanks for your reply. Do you know how to generate PropertiesChanged
signal after updating 'Value' successfully using C , which
API/function should I use/try?

Thanks
Best wishes
Yunhan

On Mon, Aug 7, 2017 at 2:52 AM, Luiz Augusto von Dentz
[off-list ref] wrote:

Hi Yunhan

On Mon, Aug 7, 2017 at 9:18 AM, Yunhan Wang [off-list ref] wrote:

quoted

Hi Luiz,

Do you have any idea about this issue?

Best wishes
Yunhan

On Sun, Aug 6, 2017 at 1:25 AM, Yunhan Wang [off-list ref] wrote:

quoted

Hi

Has any one been able to send notification from LE peripheral to LE
central using bluetoothctl?

Now I am trying to update "Value" with 0x02 for the below
characteristic with read and indicate flag, i am expecting a
notification can be sent from peripheral to central automatically. It
seems there is no such support in bluetoothctl. Then I do simple code
change on below, and try to update value via "update-chrc 0x02", well,
the value has been successfully updated, but there is no
message/notification sent from peripheral to central automatically. I
have confirmed that chrc read from central is showing updated value,
02, correctly. The question is that how can we send characteristic
notification/indication using bluez dbus API?

That is up for the application when to generate Value changes, we can
introduce a command to just do that, though using bluetoothctl to
generate notification is not very user friendly.

bluetoothd will notice if the application had update its Value, but in
order for this to work you have to generate the PropertiesChanged
signal.

quoted

quoted

btw, I see the video(BlueZ Meets Zephyr made by Luiz)
https://www.youtube.com/watch?v=SdmZX5q-XDg
In 30:05, I see Zephyr is sending notification to bluetoothctl
automatically.How can we just use bluez dbus API to achieve this?

That is using HRS and emulating the heart rate measurements.

quoted

quoted

for example,
In LE peripheral:
I setup the below characteristic with read and indicate flag
register-service 00001820-0000-1000-8000-00805f9b34fb
register-characteristic 00002a06-0000-1000-8000-00805f9b34fb read,indicate
register-application
advertise peripheral

In LE central:
connect 00:AA:01:00:00:23
select-attribute /org/bluez/hci1/dev_00_AA_01_00_00_23/service000a/char000b
notify on

The code change snippet

--- a/client/gatt.c
+++ b/client/gatt.c
-void gatt_register_chrc(DBusConnection *conn, GDBusProxy *proxy, wordexp_t *w)
+void chrc_set_value1(const char *input, void *user_data, DBusConnection *conn)
+{
+    struct chrc *chrc = user_data;
+
+    g_free(chrc->value);
+
+    chrc->value = str2bytearray((char *) input, &chrc->value_len);
+    g_dbus_emit_property_changed(conn, chrc->path,

"org.bluez.GattCharacteristic1", "Value");
+
+}
+struct chrc * gatt_register_chrc(DBusConnection *conn, GDBusProxy
*proxy, wordexp_t *w)
 {
       struct service *service;
        struct chrc *chrc;

@@ -1489,6 +1500,8 @@ void gatt_register_chrc(DBusConnection *conn,

GDBusProxy *proxy, wordexp_t *w)
        print_chrc(chrc, COLORED_NEW);

        rl_prompt_input(chrc->path, "Enter value:", chrc_set_value, chrc);
+
+    return chrc;
 }

--- a/client/main.c
+++ b/client/main.c
+static void cmd_update_chrc(const char *arg)
+{
+    chrc_set_value1(arg, default_chrc, dbus_conn);

Where does default_chrc comes from? I guess we would need some way to
select the server attributes in order to update them, again this is
not going to be user friendly since you have to send the notification
one by one. Perhaps an easier way to test this is to register standard
attributes like HRS and enable simulation, so it would act exactly
like zephyr or out example-gatt-server.

This could perhaps be done automatically in case a know service is
registered without any attributes, e.g: HRS, then by the time we
register the application bluetoothctl would take care of registering
the standard attributes for the service.

quoted

quoted

+
+}
+
static void cmd_unregister_characteristic(const char *arg)
 {
        wordexp_t w;

@@ -2541,6 +2547,9 @@ static const struct {
        { "register-characteristic", "<UUID> <Flags=read,write,notify...>",
                                        cmd_register_characteristic,
                                        "Register application characteristic" },
+    { "update-chrc", "<value.>",
+            cmd_update_chrc,
+            "update chrc value" },

Thanks
Best wishes
Yunhan

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Luiz Augusto von Dentz