The GTD8 is an 8-channel switch and LED panel from GTD IOT that communicates via Modbus TCP over Ethernet. It provides 8 independent on/off switches (H:0–H:7) and 8 corresponding LED indicators (H:10–H:17), all accessible as holding registers. 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 500 ms intervals.
Network connection
Connect the GTD8 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 GTD8 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 16 devices: 8 switches and 8 LED indicators.
Switch control (Switches 1–8)
All 8 switches operate identically. Each switch is exposed as an on/off switch in TapHome:
- Read: The switch state is read from holding registers H:0 through H:7 (one per switch)
- Write: When toggled from TapHome, the template writes the switch state to H:0–H:7 using the MODBUSWNE (write-no-echo) pattern
LED indicators (LEDs 1–8)
Each switch has a corresponding LED indicator that can be controlled independently:
- Read: The LED state is read from holding registers H:10 through H:17
- Write: LEDs can be toggled from TapHome via H:10–H:17 using MODBUSWNE
The LED indicators can be used to mirror the switch state or driven independently for custom signaling.
| Switch | Switch register | LED register | Poll interval |
|---|---|---|---|
| Switch 1 | H:0 | H:10 | 500 ms |
| Switch 2 | H:1 | H:11 | 500 ms |
| Switch 3 | H:2 | H:12 | 500 ms |
| Switch 4 | H:3 | H:13 | 500 ms |
| Switch 5 | H:4 | H:14 | 500 ms |
| Switch 6 | H:5 | H:15 | 500 ms |
| Switch 7 | H:6 | H:16 | 500 ms |
| Switch 8 | H:7 | H:17 | 500 ms |
Unlike the GTD IOT 8-Button Touch Switch (RS-485 variant), the GTD8 does not have an initialization script — no touch-to-toggle mode configuration is required. The switches and LEDs are directly readable and writable from import.
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 GTD8 are on the same network/subnet
- Check that no firewall is blocking port 502
LED not matching switch state
The GTD8 template controls switches and LEDs as independent devices. If you need LED mirroring (LED follows switch state automatically), create a TapHome Smart Rule that copies the switch state to the corresponding LED device.
