If you are just measuring ohms you can get the measurement in as little as 25 to 50 lines of code. Super easy. Not complicated at all

(This uses the RS-232 DB9 cable that comes with the UT61E.)
The following is my code and it works well, at least so far (just wrote it).
Btw, I'll will modify the code later to check for LF at end of packet to make sure it's framed properly, which only adds a few lines of code. #define PIN_DTR 32
struct Packet {
byte range;
byte digit1;
byte digit2;
byte digit3;
byte digit4;
byte digit5;
byte mode;
byte info_flags;
byte relative_mode_flags;
byte limit_flags;
byte voltage_and_autorange_flags;
byte hold;
byte cr;
byte lf;
};
struct Packet packet;
float ohms = 0.0;
void setup() {
Serial.begin(115200); // coms from arduino to mac/pc
Serial2.begin(19200, SERIAL_7O1); // seven bit word length, odd parity, one stop bit.
pinMode(PIN_DTR, OUTPUT); // DTR needs to be high to power adapter
digitalWrite(PIN_DTR, HIGH); // RTS needs to be grounded as well for powering adapter
// RX line needs to be inverted (e.g. 74HC14N) before the arduino
}
void loop() {
if (Serial2.available() > 0) {
// read in the packet
Serial2.readBytes((char *)&packet, 14);
// strip out the junk
packet.range = packet.range & B00000111; // bits 7 through 3 are always 00110
packet.digit1 = packet.digit1 & B00001111; // bits 7 through 4 are always 0011
packet.digit2 = packet.digit2 & B00001111; // bits 7 through 4 are always 0011
packet.digit3 = packet.digit3 & B00001111; // bits 7 through 4 are always 0011
packet.digit4 = packet.digit4 & B00001111; // bits 7 through 4 are always 0011
packet.digit5 = packet.digit5 & B00001111; // bits 7 through 4 are always 0011
packet.mode = packet.mode & B00001111; // bits 7 through 4 are always 0011
// do the maths
ohms = (100.0 * packet.digit1) + (10.0 * packet.digit2) + (1.0 * packet.digit3)
+ (0.1 * packet.digit4) + (0.01 * packet.digit5);
if (packet.range > 0) {
ohms = ohms * (pow(10.0, packet.range));
}
// display the result
Serial.print("Ohms: " );
if (ohms > 220000000) {
Serial.println("OL.");
} else {
Serial.println(ohms);
}
}
}
Measuring other stuff will come later. I just got this meter yesterday

But I am primarily interested in measuring Ohms of an LDR in a DIY Vactrol for all 255 PWM values the Arduino writes to the LED in the same DIY Vactrol.
I am using the following web site to help me understand the packets; couldn't of done it without the following:
https://github.com/4x1md/ut61e_pyThis could easily be adapted to STM32 and/or ESP32 etc.