Android app dev wanted?

Trapped at work!
wouldn't even care, but I need an adapter to go from USB-C to usb-a and I only know of one at my local makerspace.
Ive been struggling with creating my own Andriod app. I dont know how folks put up with it, I wrote 3 files,
built the thing and ended up with 1877+ files, and meaningless directory structures. /... and my app doesn't work. :(

well anyway, the app I want to write would send my PLC IO control commands to a PLC via USB.
which commands formatted in hex? The commands below for IDEC series PLCs.

This app:
https://play.google.com/store/search?q=usb%20serial&c=apps&hl=en_US

has macros, and I am really ansy to test it.
I wrote an arduino echo back program:

void setup() {

Serial.begin(115200);

while (!Serial) { } // wait for a connection

Serial.println("READY");

}

void loop() {

// connect phone and see if you get transmission interactions

if (Serial.available()) {

String input = Serial.readStringUntil('\n');

Serial.print("ECHO: ");

Serial.println(input);

}

which works great!

but I want to talk to the PLC now!

05 FF 30 57 79 30 30 30 30 31 2F 0D

05 FF 30 57 79 30 30 30 31 31 2E 0D

05 FF 30 57 79 30 30 30 32 31 2D 0D

05 FF 30 57 79 30 30 30 33 31 2C 0D

05 FF 30 57 79 30 30 30 34 31 2B 0D

05 FF 30 57 79 30 30 30 35 31 2A 0D

05 FF 30 57 79 30 30 30 36 31 29 0D

05 FF 30 57 79 30 30 30 37 31 28 0D

05 FF 30 57 79 30 30 30 30 30 2E 0D

05 FF 30 57 79 30 30 30 31 30 2F 0D

05 FF 30 57 79 30 30 30 32 30 2C 0D

05 FF 30 57 79 30 30 30 33 30 2D 0D

05 FF 30 57 79 30 30 30 34 30 2A 0D

05 FF 30 57 79 30 30 30 35 30 2B 0D

05 FF 30 57 79 30 30 30 36 30 28 0D

05 FF 30 57 79 30 30 30 37 30 29 0D

So i wrote some macros to send commands. but I'm stuck until 5 because I don't have some adapter.

implication of functional test:

I can write code to conduct system debugging from a cell phone... the thing every service tech has.
no more climbing on ladders with a laptop, only to connect and data collect, and still not have a network to dial out on.
this is an every day problem for many technicians. There's no internet in the building, no place to plug in, no cellular, no way to get the data off the laptop on to a phone,
the tech has a laptop, but can't install programs (ok i have solved most of that) but, its the same issue, the service reps aren't computer programmers, or IT specialist, and the sites they go to might not have reliable network connectivity. you're in a dense industrial building, that acts like shielding from every service signal, then you want to link out, but your laptop needed to run some proprietary BS software still has to connect to your phone ... its stupid, and unnecessary, and I'll Fkn fix it myself if I can ever figure out how to write a GD Android App.

in the meantime, i want to test this program for functionality. it should work.