The GTD Therm is a wall-mount HVAC thermostat panel from GTD IOT that communicates via Modbus TCP over Ethernet. It provides temperature control with current and desired temperature reading/writing, a 10-level fan speed selector, LCD display content selection, panel backlight control, and impulse touch buttons for power, fan min/max and mode cycling. TapHome connects directly to the panel over the local network — no additional gateway is required.
The template uses the MODBUSWNE (write-no-echo) pattern for all write operations and polls the device at 2500 ms intervals.
Network connection
Connect the GTD Therm panel to the same local network as TapHome Core using a standard Ethernet cable.
- Protocol: Modbus TCP
- Port: 502
- Default Slave ID: 1
Assign a static IP address to the GTD Therm in the router’s DHCP settings to prevent the address from changing after a power cycle.
Configuration
No special configuration is needed on the GTD Therm panel. The Modbus TCP interface is active by default on port 502.
When importing the template in TapHome, provide:
- IP Address — the panel’s IP on the local network (default: 192.168.0.1)
- Slave ID — Modbus slave address (default: 1)
Device capabilities
The template exposes 9 devices: a thermostat, fan speed selector, LCD display parameter, panel backlight, 4 impulse buttons and a run mode switch.
Thermostat
The thermostat device provides temperature control with two registers:
- Current temperature — read from H:30 (Int16 / 10), displays the measured room temperature in °C
- Desired temperature — read from H:31 (Int16 / 10) and writable via MODBUSWNE. The value is multiplied by 10 before writing (e.g. 22.5 °C is written as 225)
Fan speed
A multi-value switch on register H:32 with 10 selectable levels:
| Value | Name |
|---|---|
| 0 | OFF |
| 1 | MIN |
| 2 | NORMAL |
| 3 | MAX |
| 4–9 | Extended speed levels |
LCD display parameter
A multi-value switch on register H:45 that controls what the panel’s LCD screen displays:
| Value | Display content |
|---|---|
| 0 | Setpoint temperature |
| 1 | Current temperature |
| 2 | Fan speed |
| 3 | Display value |
| 4–9 | Extended display options |
Panel backlight
On/off switch on register H:24 (Bool) to control the thermostat panel backlight.
Impulse touch buttons
Four impulse-type switches that emulate physical button presses on the panel. Each sends a momentary on/off signal via MODBUSWNE:
| Button | Register | Function |
|---|---|---|
| ON/OFF | H:2 | Power on/off toggle |
| Fan Speed Min | H:3 | Set fan to minimum speed |
| Fan Speed Max | H:4 | Set fan to maximum speed |
| Mode | H:5 | Cycle through operating modes |
These impulse buttons mirror the physical touch buttons on the panel and allow triggering the same actions remotely from TapHome or via Smart Rules.
Run mode
On/off switch on register H:33 (Bool) indicating whether the thermostat is actively running (heating/cooling active).
Register summary
| Device | Register | Data type | Read/Write | Poll interval |
|---|---|---|---|---|
| Thermostat (current temp) | H:30 | Int16 (÷10) | Read | 2500 ms |
| Thermostat (desired temp) | H:31 | Int16 (÷10) | Read/Write | 2500 ms |
| Fan Speed | H:32 | Int16 | Read/Write | 2500 ms |
| Run Mode | H:33 | Bool | Read/Write | 2500 ms |
| Panel Backlight | H:24 | Bool | Read/Write | 2500 ms |
| ON/OFF Button | H:2 | Bool | Read/Write | 2500 ms |
| Fan Min Button | H:3 | Bool | Read/Write | 2500 ms |
| Fan Max Button | H:4 | Bool | Read/Write | 2500 ms |
| Mode Button | H:5 | Bool | Read/Write | 2500 ms |
| LCD Display Parameter | H:45 | Int16 | Read/Write | 2500 ms |
Troubleshooting
No Modbus communication
- Verify the Ethernet cable is connected and the panel is powered
- Confirm the panel’s IP address — check the router’s DHCP lease table
- Ensure TapHome Core and the GTD Therm are on the same network/subnet
- Check that no firewall is blocking port 502
Temperature reads as 0 or incorrect value
The thermostat uses Int16 with a ÷10 conversion. A raw register value of 225 means 22.5 °C. If readings appear 10x too high or too low, verify the template is using the correct conversion factor.
