Serial command ??

[admin]

1. suggest you use KC868-A4's digital input make for 4 buttons for test.

binary_sensor:
- platform: gpio
name: "input1"
pin:
number: 36
inverted: true

- platform: gpio
name: "input2"
pin:
number: 39
inverted: true

- platform: gpio
name: "input3"
pin:
number: 27
inverted: true

- platform: gpio
name: "input4"
pin:
number: 14
inverted: true

2. you can add these for a test:

on_...:
- uart.write: 'CD'

3. if can't work, you can try to exchange your RXD,TXD pin, such as :
uart:
tx_pin: GPIO16
rx_pin: GPIO17
baud_rate: 9600