RE: Callback on MTU change

Hung Bui — Tue, 27 Sep 2022 10:36:42 GMT

Hi Sachin,

You can declare the callback like this:

void mtu_updated(struct bt_conn *conn, uint16_t tx, uint16_t rx)
{
	printk("Updated MTU: TX: %d RX: %d bytes\n", tx, rx);
}

static struct bt_gatt_cb gatt_callbacks = {
	.att_mtu_updated = mtu_updated
};

If you want to request the MTU exchange from the nRF52's side, you can follow my example provided in this blog. The example provided at section 2.2.

static void MTU_exchange_cb(struct bt_conn *conn, uint8_t err, struct bt_gatt_exchange_params *params)
{
	if (!err) {
		LOG_INF("MTU exchange done. "); 
		payload_length=bt_gatt_get_mtu(current_conn)-3; //3 bytes ATT header
	} else {
		LOG_WRN("MTU exchange failed (err %" PRIu8 ")", err);
	}
}
static void request_mtu_exchange(void)
{	int err;
	static struct bt_gatt_exchange_params exchange_params;
	exchange_params.func = MTU_exchange_cb;

	err = bt_gatt_exchange_mtu(current_conn, &exchange_params);
	if (err) {
		LOG_WRN("MTU exchange failed (err %d)", err);
	} else {
		LOG_INF("MTU exchange pending");
	}
	

}