Reading Buffer from Software-Serial & Writing to Serial

Question

My progress so far:

#include <SoftwareSerial.h>

SoftwareSerial ttySerial(10, 11); // RX, TX
byte buffer;

void setup()
{
  // Open serial communications and wait for port to open:
  Serial.begin(115200);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Native USB only
  }

  Serial.println("Serial Initialized");

  //Set the data rate for the SoftwareSerial port
  ttySerial.begin(115200);
  ttySerial.println("tty Initialized");
}

void loop() 
{
  ttySerial.listen();
  while (ttySerial.available())
    //byte buffer = ttySerial.read();
    //Serial.write(buffer);
    Serial.write(ttySerial.read());


//    if (Serial.available())
//      ttySerial.write(Serial.read());
}

I am really confused because if I write the data as the as the buffer I have defined, the serial monitor goes crazy. If I upload the code as shown, I don't get anything weird in the monitor but the behavior is not what I expect.

I am writing to the software-serial on RX10 & TX11 (from javascript) the following data:
Buffer.from([0, 0, 4, 0, 0, 0, 0, 0]) (keystroke "a")

The Buffer.from method comes from node using the serialport npm module. (This is basically irrelevant since sending the data from Buffer.from('test') works and is output to the monitor.

As you can see, the buffer is 1 byte (the array forming the 8 bits). Why is the buffer not read as "a" in the monitor? Is it because the Micro has an abstract HID report descriptor (see below)?

Additionally, what does Serial.write(...) represent? I.e. when I close the Arduino IDE serial monitor, will my Arduino Micro automatically assume its HID function and write the data as an HID device? S

I know there are already keyboard and mouse HID libraries but I already have code that generates the raw HID data that I would prefer to utilize. Note that the buffer described above comes from the HID report descriptor for a generic keyboard i.e. the "4" is not merely the ASCII code for "a". Explained Here Maybe I can use https://www.arduino.cc/en/Reference/HID ?

Thanks in advance!

EDIT 1: This is the output I see from the code as shown (without the monitor "going crazy")

19:51:03.017 -> Serial Initialized
19:51:13.932 -> //Where I was hoping to see "a"

EDIT 2: I found the report descriptor in Keyboard.cpp:

  //  Keyboard
    0x05, 0x01,                    // USAGE_PAGE (Generic Desktop)  // 47
    0x09, 0x06,                    // USAGE (Keyboard)
    0xa1, 0x01,                    // COLLECTION (Application)
    0x85, 0x02,                    //   REPORT_ID (2)
    0x05, 0x07,                    //   USAGE_PAGE (Keyboard)

  0x19, 0xe0,                    //   USAGE_MINIMUM (Keyboard LeftControl)
    0x29, 0xe7,                    //   USAGE_MAXIMUM (Keyboard Right GUI)
    0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
    0x25, 0x01,                    //   LOGICAL_MAXIMUM (1)
    0x75, 0x01,                    //   REPORT_SIZE (1)

  0x95, 0x08,                    //   REPORT_COUNT (8)
    0x81, 0x02,                    //   INPUT (Data,Var,Abs)
    0x95, 0x01,                    //   REPORT_COUNT (1)
    0x75, 0x08,                    //   REPORT_SIZE (8)
    0x81, 0x03,                    //   INPUT (Cnst,Var,Abs)

  0x95, 0x06,                    //   REPORT_COUNT (6)
    0x75, 0x08,                    //   REPORT_SIZE (8)
    0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
    0x25, 0x73,                    //   LOGICAL_MAXIMUM (115)
    0x05, 0x07,                    //   USAGE_PAGE (Keyboard)

  0x19, 0x00,                    //   USAGE_MINIMUM (Reserved (no event indicated))
    0x29, 0x73,                    //   USAGE_MAXIMUM (Keyboard Application)
    0x81, 0x00,                    //   INPUT (Data,Ary,Abs)
    0xc0,                          // END_COLLECTION

I will need to compare this to the data I would be sending to Keyboard.write()

Answer 1

Don't use listen() this way. It clears the receive buffer. You loose the data received before listen() call.

You have only one SoftwareSerial instance so you don't need to call listen(). The listen() function clears the receive buffer because there is only one buffer for all SoftwareSerial instances.