I want to send signals to Bela from an external device to PD width UART(tx,rx).
Because IDE Libraries Expamples(Serial Communication/serial) worked well,
I am thinking of starting PD with render.cpp and sending the signals received on render.cpp to PD.
But I don't know what to do specifically.
How to write the code for render.cpp.

Look also at the example PureData/uart-communication to see how you can get data in and out of Pd without using C++.

uart-communication is not in Examples/PureData, do I need to update IDE?

---Examples/PureData----
language-overview
hello-sound
digital-out
digital-in
analog-in
analog-out
am-synthesis
fm-synthesis
drum-synthesis
rubber-duckie
delay-effect
samples-playback
samples-record
pitch-tracking
talk-back
karplus-strong
capacitive-sensing
diy-pressure-sensors
accelerometer
ultrasonic-distance-sensor
oscilloscope
gui-send
gui-receive
hello-midi
midi-cv-midi
osc-receive
osc-send
custom-render
custom-render-ultrasonic-distance-sensor
digital-advanced
envelope-trigger
monophonic-synth
multiplexer-capelet
sample-scrub

Version details v0.3.8g
I can't find PureData/uart-communication, where is it?

    John Version details v0.3.8g

    it should say much more than that, e.g.: