Reading Hex data over serial

[derkernel]

Hello everyone.
I'm trying to receive a hexadecimal frame over serial from a stepper motor and print its data values in the serial monitor.

The stepper is a closed loop package from BIGTREETECH, it's their S57B model. The package comes with a 32 Bit microprocessor and their own custom firmware.
They specified a protocol that has the following format:

This is how far I've gotten with my experiments:
Command for the read request as per the specified protocol:

void sendReadRequest() {
    const size_t packet_length = 8;
    uint8_t packet[packet_length] = {0xFE, 0xFE, 0x05, 0xB0, 0xAA, 0xAA, 0x09, 0x16};
    Serial.write(packet, packet_length);
}

And on the reading side of things:

void loop() {
    if (Serial.available() > 0) {
        incomingByte = Serial.read();

        Serial.print("I received: ");
        Serial.println(incomingByte, HEX);
  }
}

There is only some gibberish being printed in the console, so I'm guessing it's in the wrong format and/or is being read in the wrong way. Maybe a Serial.readBytesUntil() would work?

I know that the command for the request must be right tho, because whenever I send it, there is something being printed in the serial monitor.

Thank you guys in advance!

PS: I should also mention that there is an SPI and CAN interface available as well from the stepper. However, since documentation is sparse I do not know how to really use them.
Here is a link to the docs for the stepper: BIGTREETECH-Stepper-Motor-Driver/S57B at master · bigtreetech/BIGTREETECH-Stepper-Motor-Driver · GitHub

[MaximoEsfuerzo]

Have you set the terminal to 38400 baud?

[jremington]

@derkernel

        Serial.print("I received: ");
        Serial.println(incomingByte, HEX);

That is a lot of printing for every single character that comes in. I wonder if it can keep up, given that the serial monitor data rate cannot exceed 115200 Baud.

[johnwasser]

How are you using Serial to both send binary to your S57 and send text to Serial Monitor?!?

[derkernel]

I tried it without the "I received: " part as well, so that doesn't seem to be the problem. I think it is just a formatting issue of some sort, or that I'm reading the incoming data in the wrong way..