Control the HD44780 using HTTP/MQTT.
I use this library.
It's great work.
I made this to know if there are any notify on my HEAD LESS linux server.

ESP-IDF V4.4/V5.0.

Character display using HD44780.
Usually called 1602LCD/1604LCD.

git clone https://github.com/nopnop2002/esp-idf-remote-hd44780
cd esp-idf-remote-hd44780
git clone https://github.com/UncleRus/esp-idf-lib.git
idf.py menuconfig
idf.py flash

You can connect using the mDNS hostname instead of the IP address.

You can use static IP.

Using HTTP

Using MQTT

The initial value is no backlight control.

(*1) You can change any GPIO using menuconfig.

(*2) 5V for 5V modules. 3.3V for 3.3V modules.

• cursor:off blink:off(default)
  curl -X POST -H "Content-Type: application/json" -d '{"lcd":"on", "cursor":"off", "blink":"off"}' http://esp32-server.local:8080/api/control

• cursor:on blink:off
  curl -X POST -H "Content-Type: application/json" -d '{"lcd":"on", "cursor":"on", "blink":"off"}' http://esp32-server.local:8080/api/control

• cursor:off blink:on
  curl -X POST -H "Content-Type: application/json" -d '{"lcd":"on", "cursor":"off", "blink":"on"}' http://esp32-server.local:8080/api/control

• cursor:on blink:on
  curl -X POST -H "Content-Type: application/json" -d '{"lcd":"on", "cursor":"on", "blink":"on"}' http://esp32-server.local:8080/api/control

• clear lcd
  curl -X POST -H "Content-Type: application/json" http://esp32-server.local:8080/api/clear

• set position
  curl -X POST -H "Content-Type: application/json" -d '{"col":0, "line":0}' http://esp32-server.local:8080/api/gotoxy

• put character on lcd
  curl -X POST -H "Content-Type: application/json" -d '{"char":"s"}' http://esp32-server.local:8080/api/putc

• put string on lcd
  curl -X POST -H "Content-Type: application/json" -d '{"str":"abcdefghijklmn"}' http://esp32-server.local:8080/api/puts

• backlight on
  curl -X POST -H "Content-Type: application/json" -d '{"backlight":"on"}' http://esp32-server.local:8080/api/backlight

• backlight off
  curl -X POST -H "Content-Type: application/json" -d '{"backlight":"off"}' http://esp32-server.local:8080/api/backlight

A transistor is required for backlight control.

                  emitter
ESP32 GND -----------------+
                           |
                    base   /
ESP32 BL  -----^^^--------|    SS8050
                           \
               collector   |
                           +------- LCD K
ESP32 3.3V/5V --------------------- LCD A

sudo apt install curl
bash ./demo_http.sh

• cursor:off
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/cursor" -m "off"

• cursor:on
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/cursor" -m "on"

• blink:off
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/blink" -m "off"

• blink:on
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/blink" -m "on"

• clear lcd
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/clear" -m ""

• set column
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/col" -m "0"

• set line
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/line" -m "0"

• put character on lcd
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/putc" -m "s"

• put string on lcd
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/puts" -m "abcdefghijklmn"

• backlight on
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/backlight" -m "on"

• backlight off
  mosquitto_pub -h broker.emqx.io -p 1883 -t "/api/hd44780/backlight" -m "off"

sudo apt install mosquitto-clients
bash ./demo_mqtt.sh