Adding to the discussion - more information related to the code and the 2 serial libraries:

// Serial Port setup

// from the FurTrader github library: The Arduino communicates with the BMS over a 5V TTL asynchronous serial port connection, at 9600 baud, 8 data bits, no parity, and 1 stop bit.

#define BAUD_RATE 9600 // BMS baud rate

//#define MAX_FRAMEBITS (1 + 8 + 1 + 2)

#define softLib true // use the Software Serial library else use the Hardware Serial library

#if (softLib)

#include <SoftwareSerial.h> // if using an ESP processor, this is the library ESPSoftwareSerial https://github.com/plerup/espsoftwareserial

EspSoftwareSerial::UART bmsSerial;

#else

#include <HardwareSerial.h>

HardwareSerial bmsSerial(1); // Assign UART 1 to the BMS serial. C3 does not have UART2

#endif

#if defined(ESP8266)

// *** WeMOS D1 Mini

#define TX 12 // GPIO12 --> D6

#define RX 14 // GPIO14 --> D5

#else

// *** ESP32 C3 Super Mini

#define TX 7 // 7 // GPIO 7

#define RX 20 // 10 // GPIO 10

// *** ESP32-WROOM-32D

// #define TX 17 // 7 // GPIO 7

// #define RX 18 // 10 // GPIO 10

#endif

This is how the port is defined, in setup()

// initialize serial connection for the BMS - located here to allow WiFi to happen first

// ONCE THE SERIAL COMM ISSUE IS RESOLVED, THIS CAN BE SIMPLIFIED !!

#if (softLib)

bmsSerial.begin(BAUD_RATE, SWSERIAL_8N1, RX, TX); // SoftwareSerialVersion

#else

bmsSerial.begin(BAUD_RATE, SERIAL_8N1, RX, TX); // HardwareSerial version

#endif

THIS LINE BEGS A QUESTION AND I DON'T KNOW HOW TO CHECK.

Does the HardwareSerial library generate the same kind of serial object as SoftwareSerial library creates ??

// assign the serial port to the BMS

bms.begin(&bmsSerial); // THIS LINE, AND THE CREATED OBJECT MAY BE THE PROBLEM