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
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.
