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+--- Thread: Connecting Nextion NX3224K028 HMI display to KC868-A16S? (/showthread.php?tid=9179)
Connecting Nextion NX3224K028 HMI display to KC868-A16S? - markusd1984 - 03-27-2026
Is it officially supported to connect a Nextion HMI display (NX3224K028) via UART to the KC868-A16S?
If yes, I need clarification on how to wire it safely:
- Which pins for TX/RX? I know I cannot use the I2C header (GPIO 4/5) because it runs the PCF8574 relay chips.
- The Boot Issue: If I use the GSM header (GPIO 13/15), how do I prevent the ESP32 from failing to boot? (Since GPIO 15 is a strapping pin and Nextion holds it HIGH).
- Power & Pinout: Where is the safest place to pull 5V/GND, and what is the exact physical pin order on the board so I wire my custom cable correctly?
I want to use it as a backup to control the relays in case HA / network is offline (to manage my heating thermal actuators).
Thanks in advance!
RE: Connecting Nextion NX3224K028 HMI display to KC868-A16S? - admin - 03-28-2026
if you don't use 4G module, you can use GSM RXD,TXD for Nextion display.
GSM:
RXD:GPIO15
TXD:GPIO13
5V also can get from 4G module socket, there is "V" is 5v. T is "TXD". R is "RXD"