# Help building app **URL:** \ **Category:** Questions & Help\ **Tags:** app\ **Created:** [February 28, 2026, 4:02pm UTC](https://community.homey.app/t/help-building-app/151845 "2026-02-28T16:02:47Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Bas\_Van\_der\_Putten](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/bas_van_der_putten/32/120799_2.png) [@Bas\_Van\_der\_Putten](https://community.homey.app/u/Bas_Van_der_Putten)\ **Post date:** [February 28, 2026, 4:02pm UTC](https://community.homey.app/t/help-building-app/151845/1 "2026-02-28T16:02:47Z")
Hi all, I have a android built in wall display with led lights, gpo ports, 2relais and temperature and humidity sensor. I do have the API documents, but don’t know how to build an app for it. It’s also possible to connect via MQTT. Is there someone who could help me? ---
**Author:** ![DirkG](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/dirkg/32/118897_2.png) [@DirkG](https://community.homey.app/u/DirkG)\ **Post date:** [February 28, 2026, 4:55pm UTC](https://community.homey.app/t/help-building-app/151845/2 "2026-02-28T16:55:40Z")
You can request an app here: > [@\[Requests\] Homey Pro Community App Requests](https://community.homey.app/t/requests-homey-pro-community-app-requests/2713): > > Homey Pro Community App Requests Welcome to the Homey Pro Community app request topic. This topic is to centralize all app requests for Homey Pro Apps, made by the community. (This does not account for app(s) for Homey (bridge), only for the Homey Pro, as Athom only wants apps made by brands or by themselves.) For Requests at Athom please use the Official link in the Appstore, see the description in this Topic: [[Requests] Official Homey App and Device Request](https://community.homey.app/t/requests-official-homey-app-and-device-request/103771) The more information that you… Do you have any knowledge about MQTT? ---
**Author:** ![Bas\_Van\_der\_Putten](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/bas_van_der_putten/32/120799_2.png) [@Bas\_Van\_der\_Putten](https://community.homey.app/u/Bas_Van_der_Putten)\ **Post date:** [February 28, 2026, 5:07pm UTC](https://community.homey.app/t/help-building-app/151845/3 "2026-02-28T17:07:19Z")
Thanks, i will repost it there. I am complete new to mqtt. Did read a lot but never really did something with that. ---
**Author:** ![smarthomesven](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/smarthomesven/32/79712_2.png) [@smarthomesven](https://community.homey.app/u/smarthomesven)\ **Post date:** [February 28, 2026, 5:47pm UTC](https://community.homey.app/t/help-building-app/151845/4 "2026-02-28T17:47:03Z")
What’s the product name? > [@Bas\_Van\_der\_Putten](#): > > I do have the API documents Can you share these? ---
**Author:** ![Bas\_Van\_der\_Putten](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/bas_van_der_putten/32/120799_2.png) [@Bas\_Van\_der\_Putten](https://community.homey.app/u/Bas_Van_der_Putten)\ **Post date:** [February 28, 2026, 6:22pm UTC](https://community.homey.app/t/help-building-app/151845/5 "2026-02-28T18:22:25Z")
cid=client\_id prefix=homeassistant base=client\_id static void init\_topics(const char\* base) { ``` // 灯光 snprintf(light_state_topic, sizeof(light_state_topic), "%s/light/status", base); snprintf(light_command_topic, sizeof(light_command_topic), "%s/light/switch", base); snprintf(brightness_state_topic, sizeof(brightness_state_topic), "%s/brightness/status", base); snprintf(brightness_command_topic, sizeof(brightness_command_topic), "%s/brightness/set", base); snprintf(rgb_state_topic, sizeof(rgb_state_topic), "%s/rgb/status", base); snprintf(rgb_command_topic, sizeof(rgb_command_topic), "%s/rgb/set", base); // 传感器 snprintf(temp_state_topic, sizeof(temp_state_topic), "%s/sensors/temperature", base); snprintf(hum_state_topic, sizeof(hum_state_topic), "%s/sensors/humidity", base); // 开关 snprintf(switch1_state_topic, sizeof(switch1_state_topic), "%s/switch1/status", base); snprintf(switch1_command_topic, sizeof(switch1_command_topic), "%s/switch1/set", base); snprintf(switch2_state_topic, sizeof(switch2_state_topic), "%s/switch2/status", base); snprintf(switch2_command_topic, sizeof(switch2_command_topic), "%s/switch2/set", base); ``` } // ========= ③ 统一发布 5 个实体的 Discovery ========= static void publish\_ha\_discovery(const char\* cid, const char\* prefix /\*通常为"homeassistant"\*/) { ``` char topic\[256\]; char payload\[1024\]; char dev\[256\]; make_device_json(dev, sizeof(dev), cid); ``` printf(“------%s------\n”,prefix); ``` // ------- light (支持 开关/亮度/RGB) ------- snprintf(topic, sizeof(topic), "%s/light/%s_rgb1/config", prefix, cid); snprintf(payload, sizeof(payload), "{" "\\"name\\":\\"%s RGB\\"," "\\"unique_id\\":\\"%s_rgb1\\"," "\\"command_topic\\":\\"%s\\"," "\\"state_topic\\":\\"%s\\"," "\\"state_value_template\\":\\"{{ value_json.state }}\\"," "\\"brightness_command_topic\\":\\"%s\\"," "\\"brightness_state_topic\\":\\"%s\\"," "\\"brightness_value_template\\":\\"{{ value_json.brightness }}\\"," "\\"rgb_command_topic\\":\\"%s\\"," "\\"rgb_state_topic\\":\\"%s\\"," "\\"rgb_value_template\\":\\"{{ value_json.rgb\[0\] }},{{ value_json.rgb\[1\] }},{{ value_json.rgb\[2\] }}\\"," "\\"payload_on\\":\\"ON\\"," "\\"payload_off\\":\\"OFF\\"," "%s" "}", cid, cid, light_command_topic, light_state_topic, brightness_command_topic, brightness_state_topic, rgb_command_topic, rgb_state_topic, dev ); publish_config_retained(topic, payload); // ------- switch1 ------- snprintf(topic, sizeof(topic), "%s/switch/%s_switch1/config", prefix, cid); snprintf(payload, sizeof(payload), "{" "\\"name\\":\\"%s Switch1\\"," "\\"unique_id\\":\\"%s_switch1\\"," "\\"command_topic\\":\\"%s\\"," "\\"state_topic\\":\\"%s\\"," "\\"value_template\\":\\"{{ value_json.state }}\\"," "\\"payload_on\\":\\"ON\\"," "\\"payload_off\\":\\"OFF\\"," "%s" "}", cid, cid, switch1_command_topic, switch1_state_topic, dev ); publish_config_retained(topic, payload); // ------- switch2 ------- snprintf(topic, sizeof(topic), "%s/switch/%s_switch2/config", prefix, cid); snprintf(payload, sizeof(payload), "{" "\\"name\\":\\"%s Switch2\\"," "\\"unique_id\\":\\"%s_switch2\\"," "\\"command_topic\\":\\"%s\\"," "\\"state_topic\\":\\"%s\\"," "\\"value_template\\":\\"{{ value_json.state }}\\"," "\\"payload_on\\":\\"ON\\"," "\\"payload_off\\":\\"OFF\\"," "%s" "}", cid, cid, switch2_command_topic, switch2_state_topic, dev ); publish_config_retained(topic, payload); // ------- temperature sensor ------- snprintf(topic, sizeof(topic), "%s/sensor/%s_temperature/config", prefix, cid); snprintf(payload, sizeof(payload), "{" "\\"name\\":\\"%s Temperature\\"," "\\"unique_id\\":\\"%s_temperature\\"," "\\"state_topic\\":\\"%s\\"," "\\"value_template\\":\\"{{ value_json.temperature }}\\"," "\\"unit_of_measurement\\":\\"°C\\"," "\\"device_class\\":\\"temperature\\"," "\\"state_class\\":\\"measurement\\"," "%s" "}", cid, cid, temp_state_topic, dev ); publish_config_retained(topic, payload); // ------- humidity sensor ------- snprintf(topic, sizeof(topic), "%s/sensor/%s_humidity/config", prefix, cid); snprintf(payload, sizeof(payload), "{" "\\"name\\":\\"%s Humidity\\"," "\\"unique_id\\":\\"%s_humidity\\"," "\\"state_topic\\":\\"%s\\"," "\\"value_template\\":\\"{{ value_json.humidity }}\\"," "\\"unit_of_measurement\\":\\"%%\\"," "\\"device_class\\":\\"humidity\\"," "\\"state_class\\":\\"measurement\\"," "%s" "}", cid, cid, hum_state_topic, dev ); publish_config_retained(topic, payload); ``` } ---
**Author:** ![Bas\_Van\_der\_Putten](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/bas_van_der_putten/32/120799_2.png) [@Bas\_Van\_der\_Putten](https://community.homey.app/u/Bas_Van_der_Putten)\ **Post date:** [February 28, 2026, 6:26pm UTC](https://community.homey.app/t/help-building-app/151845/6 "2026-02-28T18:26:35Z")
The model is rk3576\_u also named as smt101 ---
**Author:** ![Bas\_Van\_der\_Putten](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/bas_van_der_putten/32/120799_2.png) [@Bas\_Van\_der\_Putten](https://community.homey.app/u/Bas_Van_der_Putten)\ **Post date:** [February 28, 2026, 6:28pm UTC](https://community.homey.app/t/help-building-app/151845/7 "2026-02-28T18:28:30Z")
This is al the info i have, hopes that’s enough? ---
**Author:** ![smarthomesven](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/smarthomesven/32/79712_2.png) [@smarthomesven](https://community.homey.app/u/smarthomesven)\ **Post date:** [February 28, 2026, 6:36pm UTC](https://community.homey.app/t/help-building-app/151845/8 "2026-02-28T18:36:38Z")
What’s the MQTT broker domain? Maybe it’s in the environment variables? You didn’t mention the domain/base URL of this MQTT broker. ---
**Author:** ![smarthomesven](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/smarthomesven/32/79712_2.png) [@smarthomesven](https://community.homey.app/u/smarthomesven)\ **Post date:** [February 28, 2026, 6:44pm UTC](https://community.homey.app/t/help-building-app/151845/9 "2026-02-28T18:44:04Z")
And how do you authenticate? Is the MQTT username the email address of your account there? Also, what’s the name of the mobile/web app that you control it with? ---
**Author:** ![Bas\_Van\_der\_Putten](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/bas_van_der_putten/32/120799_2.png) [@Bas\_Van\_der\_Putten](https://community.homey.app/u/Bas_Van_der_Putten)\ **Post date:** [February 28, 2026, 6:46pm UTC](https://community.homey.app/t/help-building-app/151845/10 "2026-02-28T18:46:16Z")
Can we private message each other here? Maybe thats more easy