Communication / Bluetooth

MiniHPC can read data from compatible Bluetooth devices in the household that are located nearby.
From these devices, it can read the ambient air temperature T1 and humidity, from which MiniHPC then calculates the dew point. Based on this, it adjusts the cooling limit temperatures so that they do not exceed the dew point and prevent condensation problems on surfaces.
These sensors can also serve as a full replacement for the NTC room temperature sensor T1 and can therefore be used as wireless thermostats.
Reading data from compatible BT devices needs to be enabled in the menu 2.6 Dew point / BT sensor

All BT sensors with the custom firmware ATC_MiThermometer supporting the advertising type BTHome v2 (or PVVX) are supported. These include, for example, Xiaomi Mijia temperature sensors (LYWSD03MMC, MJWSD05MMC), or some supported Tuya temperature sensors.

The BT sensor can be flashed with custom firmware simply by uploading new firmware via the web flasher TelinkMiFlasher if the Xiaomi Mijia device contains an older original FW version up to 1.5.

For the newer original firmware version 2.1.1 the procedure is more complicated. We recommend checking the github pages of the firmware author for more details, or the following video.

After flashing the custom FW into the BT sensor, it is necessary to set the parameter Advertising type to BTHome v2.

Multiple sensors in the household

MiniHPC can read data from up to 10 supported temperature sensors simultaneously. From the measured temperature and humidity values, it calculates the average temperature and humidity (or minimum/maximum, depending on the setting). This calculated temperature will then replace the T1 temperature sensor.

The list of available sensors with their measured values can be accessed by opening the device’s IP address in the Bluetooth menu.

In this section of the MiniHPC configuration, it is possible to enable/disable individual sensors, change the name and assign them weight values for the average calculation. For example, for a temperature sensor located in a larger room, you can assign a higher weight, so its reading will have greater influence on the average. If a sensor is disabled, its value will still be displayed in the table but will not be included in the calculation.

A sensor that has been stored in the database but has not sent data for more than 60 minutes is considered lost and can be deleted from the database by clicking the trash icon on the right side of the table.

At line Calculate by:, you can set whether the calculation should be based on the average, or whether the maximum/minimum measured temperature should be used. This can be configured separately for temperature and humidity.

The option Activate new sensors defines whether newly discovered sensors will be activated automatically (ideal if they are used only for MiniHPC), or whether they need to be activated manually. Manual activation is useful in cases where the user has more BTHome v2 temperature sensors in the household and does not want newly added ones to be automatically included in the MiniHPC temperature/humidity calculation.

Cloud upload interval: Sets how often Bluetooth data are uploaded to On-line cloud. One MiniHPC has space for approximately 5000 Bluetooth records on the Cloud portal. One thermometer with a 1-minute upload interval generates 1440 records per day, so older data will be overwritten after about 3 days. If 3 thermometers are connected to MiniHPC, they will exhaust the 5000 record limit in about 28 hours at a 1-minute upload interval. Therefore, if uploading data every minute is not necessary (for example for diagnostic purposes), we recommend increasing this interval to 5 minutes or more.

Xiaomi MJWSD05MMC as a Thermostat

Xiaomi MJWSD05MMC (Xiaomi Smart Temperature and Humidity Monitor 3) has two buttons on its right side. In the standard ATC firmware, these buttons are used to switch screens and enable Bluetooth communication.

The modified ATC firmware BTE_v56_thermostat.bin changes the function of these buttons and also modifies the information displayed on the screens. It adds a new function that allows the desired temperature to be set directly on the thermometer. This value is then transmitted to MiniHPC using the BThome v2 protocol.

Button functions in the modified ATC firmware:

• The up/down buttons adjust the set temperature with a short press. The adjustment resolution can be configured on the third screen.
• A long press of the upper button switches between screens.
• A long press of the lower button activates the option to immediately connect to the thermometer via Bluetooth.

Screen description:

• Screen 1 displays the set temperature as the main value. The bottom row shows the date, measured temperature, and measured air humidity.
• Screen 2 displays the measured temperature as the main value. The bottom row shows the date, set temperature, and measured relative humidity.
• Screen 3 displays the configured resolution (how many °C the set temperature changes when the buttons are pressed), with the option to adjust this resolution. The bottom row shows the date, battery voltage in V or mV (when below 3000 mV), and battery level in percent.

The temperature set on the thermometer is periodically transmitted to MiniHPC using the BThome v2 protocol. In the web interface, this set temperature can be displayed and its parameters can also be adjusted.

By clicking on the temperature, you can select which temperature setting it will control. Five options are available:

• Off – by default, this temperature does not affect settings in MiniHPC
• T1 – The temperature sets the indoor temperature T1 configured in menu 1.2 Control temperature by
• TWh – The temperature sets the heating water temperature T2 or T3 according to the configuration in menu 1.2 Control temperature by
• TWc – The temperature sets the cooling water temperature T3 configured in menu 2.2 Control temperature by
• T5 – The temperature adjusts the DHW target temperature configured in menu 3.1 DHW temperatures

Additional options are also available for processing thermometer data:

• Bi-directional sync [S] – Enabling this option activates bidirectional synchronization between MiniHPC and the thermometer. After each temperature change on MiniHPC, the change will also be reflected on the connected thermometer.
• Apply timers [T] – This option allows adjustment of the base temperature value reduced by the currently applied timer offset. Enabling this option together with bidirectional synchronization updates the temperature on the thermometer whenever it is modified by a timer.