From 32b985fcd46f0e6afeb7184c9b1cf678ad6a1109 Mon Sep 17 00:00:00 2001
From: Matthias Ringwald <matthias@ringwald.ch>
Date: Mon, 17 Mar 2025 13:23:59 +0100
Subject: [PATCH] hid_keyboard_demo: Reconnect to last bonded device on startup

---
 CHANGELOG.md                |  1 +
 example/hid_keyboard_demo.c | 38 ++++++++++++++++++++++++++++++++++---
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ecaada63c..790274c9a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - POSIX: support error condition for file descriptors in btstack_run_loop
 - Linux: HCI Transport for Linux HCI Kernel Socket
 - Linux: Audio sink implementation for Linux ALSA
+- HID Keyboard Demo: Reconnect to last bonded device on startup
 
 ### Fixed
 - HCI: fix incorrect assert/regression in num completed packets handling introduced in 6ec1ca0
diff --git a/example/hid_keyboard_demo.c b/example/hid_keyboard_demo.c
index 4686fd05b..7548bb380 100644
--- a/example/hid_keyboard_demo.c
+++ b/example/hid_keyboard_demo.c
@@ -47,6 +47,7 @@
 // *****************************************************************************
 
 
+#include <btstack_tlv.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -70,6 +71,9 @@
 static uint16_t host_max_latency = 1600;
 static uint16_t host_min_timeout = 3200;
 
+// TAG to store remote device address in TLV
+#define TLV_TAG_HIDR ((((uint32_t) 'H') << 24 ) | (((uint32_t) 'I') << 16) | (((uint32_t) 'D') << 8) | 'R')
+
 #define REPORT_ID 0x01
 
 // close to USB HID Specification 1.1, Appendix B.1
@@ -199,6 +203,10 @@ static bd_addr_t device_addr;
 static const char * device_addr_string = "BC:EC:5D:E6:15:03";
 #endif
 
+// used to store remote device in TLV
+static const btstack_tlv_t * btstack_tlv_singleton_impl;
+static void *                btstack_tlv_singleton_context;
+
 static enum {
     APP_BOOTING,
     APP_NOT_CONNECTED,
@@ -275,6 +283,20 @@ static void queue_character(char character){
 
 // Demo Application
 
+static void hid_start_reconnect(void){
+    // check if we have a bonded device
+    // used to store remote device in TLV
+    if (btstack_tlv_singleton_impl){
+        int len = btstack_tlv_singleton_impl->get_tag(btstack_tlv_singleton_context, TLV_TAG_HIDR, (uint8_t *) &device_addr, sizeof(bd_addr_t));
+        if (len == sizeof(device_addr)){
+            printf("Bonded, reconnect to device with address %s ...\n", bd_addr_to_str(device_addr));
+            hid_device_connect(device_addr, &hid_cid);
+            return;
+        }
+    }
+    printf("Please connect to HID Keyboard Demo from smartphone or computer.\n");
+}
+
 #ifdef HAVE_BTSTACK_STDIN
 
 // On systems with STDIN, we can directly type on the console
@@ -336,6 +358,8 @@ static void packet_handler(uint8_t packet_type, uint16_t channel, uint8_t * pack
                 case BTSTACK_EVENT_STATE:
                     if (btstack_event_state_get_state(packet) != HCI_STATE_WORKING) return;
                     app_state = APP_NOT_CONNECTED;
+                    btstack_tlv_get_instance(&btstack_tlv_singleton_impl, &btstack_tlv_singleton_context);
+                    hid_start_reconnect();
                     break;
 
                 case HCI_EVENT_USER_CONFIRMATION_REQUEST:
@@ -357,10 +381,18 @@ static void packet_handler(uint8_t packet_type, uint16_t channel, uint8_t * pack
                             }
                             app_state = APP_CONNECTED;
                             hid_cid = hid_subevent_connection_opened_get_hid_cid(packet);
-#ifdef HAVE_BTSTACK_STDIN                        
-                            printf("HID Connected, please start typing...\n");
+                            hid_subevent_connection_opened_get_bd_addr(packet, device_addr);
+
+                            // store device as bonded
+                            if (btstack_tlv_singleton_impl){
+                                btstack_tlv_singleton_impl->store_tag(btstack_tlv_singleton_context, TLV_TAG_HIDR, (const uint8_t *) &device_addr, sizeof(bd_addr_t));
+                            }
+
+
+#ifdef HAVE_BTSTACK_STDIN
+                            printf("HID Connected to %s, please start typing...\n", bd_addr_to_str(device_addr));
 #else                        
-                            printf("HID Connected, sending demo text...\n");
+                            printf("HID Connected to %s, sending demo text...\n", bd_addr_to_str(device_addr));
                             demo_text_timer_handler(NULL);
 #endif
                             break;