Helper class for writing format format to the << operator of mwx::stream. In the library, it is alias defined as Using format=mwx::mwx_format;.

Serial << format("formatted print: %.2f", (double)3123 / 100.) << mwx::crlf;

// formatted print: 31.23[改行]

• Store the argument list received in the constructor in a variable internal to the class using the expand function of the parameter pack.

• Call fctprintf() at the point operator << is called to write data to the stream

Constructor

format(const char *fmt, ...)

The constructor stores the format pointer and parameters. The subsequent call with the << operator interprets the format and processes the output.

Flush the output buffer of mwx::stream. Instance to a helper class that calls the flush() method.

for (int i = 0; i < 127; ++i) {
    Serial << "hello world! (" << i << ")" << twe::endl << twe::flush;
}

• For serial ports, wait polling until output completes.

• For mwx::simpbuf buffers, output 0x00 at the end (size is not changed)

Instance of a helper class to output a newline code (CR LF) for the << operator of mwx::stream.

Serial << "hello world!" << mwx::crlf;

stream_helper is a helper object that grants the mwx::stream interface. It creates a helper object that references a data class and performs data input/output via the helper object.

The following creates a helper object bs from an array b of smplbufs and inputs data using the mwx::stream::operator <<() operator.

smplbuf_u8<32> b;
auto&& bs = b.get_stream_helper(); // helper object

// Data String Generation
uint8_t FOURCHARS[]={'A', 'B', 'C', 'D'};
bs << FOURCHARS;
bs << ';';
bs << uint32_t(0x30313233); // "0123"
bs << format(";%d", 99);

Serial << b << crlf; // Output to Serial via smplbuf_u8<32> class

//result: ABCD;0123;99

Overview

stream_helper behaves as if the data array were a stream.

Internally, it holds read/write positions in the data array. It behaves as follows.

• After the last data is read or written, it moves to the next read/write position.

• After the last data is read or data is appended to the end, the read/write position becomes the end.

• If the read/write position is the end of the line, then

  • available() becomes false.

  • Read cannot be performed.

  • Writing is appended if it is within the writable range.

generating stream_helper

stream_helper is a data class (smplbuf, EEPROM) member functions.

auto&& obj_helper = obj.get_stream_helper()
// obj is an object of data class, obj_helper type is accepted by auto&& because it is long.

methods

rewind()

void rewind()

Moves the read/write position to the beginning.

seek()

int seek(int offset, int whence = MWX_SEEK_SET)

Set the read/write position.

tell()

int tell()

Returns the read/write position. Returns -1 for the end position.

available()

int available()

Returns 0 if the read/write position is the end. If it is not the end, it returns any other value.

Helper class for mwx::stream << operator to output numeric types as big-endian byte strings.

Serial << mwx::bigendian(0x1234abcdUL);

// output binary -> 0x12 0x34 0xab 0xcd

constructor

template <typename T>
bigendian::bigendian(T v)

Upper-level class that handles input/output streams.

• Interfaces to several classes (Serial, Wire, SPI, smplbuf) by polymorphism using CRTP (Curiously Recurring Template Pattern) method.

  • In CRTP, lower classes are defined as template class Derived : public stream<Derived>; and methods of lower classes are referenced from upper classes.

• This class defines common processing such as print method, << operator, etc., and calls write() method, etc. implemented in lower classes, which is similar to using virtual functions.

Interfaces (implemented in lower classes)

Lower classes implement the functions listed below.

available()

int available()

// example
while(Serial.available()) {
  int c = Serial.read();
  // ... any
}

Returns 1 if the input exists, 0 if it does not.

flush()

void flush()

// example
Serial.println("long long word .... ");
Serial.flush();

Flush output (wait for output to complete).

read()

int read()

// example
int c;
while (-1 != (c = read())) {
    // any
}

Inputs 1-byte data from the stream. If the data does not exist, return -1.

write()

size_t write(int c)

// example
Serial.write(0x30);

Outputs 1 byte to the stream.

vOutput()

static void vOutput(char out, void* vp)

This is a static function that produces a single byte output. Since this is not a class method, member variables and other information are not available. Instead, a pointer to the class instance is passed to vp, which is passed as a parameter.

This static function is used internally and the function pointer is passed as a one-byte output function of fctprintf(). This is used to implement the print method, etc.

Interface

putchar()

void mwx::stream::putchar(char c)

// example
Serial.putchar('A');
// result -> A

Output a single byte.

print(), println()

size_t print(T val, int base = DEC) // T: 整数型
size_t print(double val, int place = 2)
size_t print(const char*str)
size_t print(std::initializer_list<int>)

// example
Serial.print("the value is ");
Serial.print(123, DEC);
Serial.println(".");
// result -> the value is 123.

Serial.print(123.456, 1);
// result -> 123.5

Serial.print({ 0x12, 0x34, 0xab, 0xcd });
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.

Performs various types of formatted output.

printfmt()

size_t printfmt(const char* format, ...);

// example 
Serial.printfmt("the value is %d.", 123);
// result -> the value is 123.

Prints output in printf format.

TWESDK/TWENET/current/src/printf/README.md 参照

operator <<

// examples
Serial << "this value is" // const char*
       << int(123)
       << '.';
       << mwx::crlf;
// result -> this value is 123.

Serial << fromat("this value is %d.", 123) << twe::crlf;
// result -> this value is 123.

Serial << mwx::flush; // flush here

Serial << bigendian(0x1234abcd);
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.

Serial << int(0x30) // output 0x30=48, "48"
       << '/'
       << uint8_t(0x31); // output '1', not "48"
// result -> 48/1

smplbuf<char,16> buf = { 0x12, 0x34, 0xab, 0xcd };
Serail << but.to_stream();
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.

Seiral << make_pair(buf.begin(), buf.end());
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.

Serial << bytelist({ 0x12, 0x34, 0xab, 0xcd });
// will output 4byte of 0x12 0x34 0xab 0xcd in binary.

set_timeout(), get_error_status(), clear_error_status()

uint8_t get_error_status()
void clear_error_status()
void set_timeout(uint8_t centisec)

// example
Serial.set_timeout(100); // 1000msのタイムアウトを設定
uint8_t c;
Serial >> c;

Manages input timeouts and errors using the >> operator.

The timeout period is specified by set_timeout(), and input is processed using the >> operator. If no input is received within the given timeout period, the error value can be read out with get_error_status(). The error status is cleared by clear_error_status().

Error Value

operator >>

inline D& operator >> (uint8_t& v)
inline D& operator >> (char_t& v)
template <int S> inline D& operator >> (uint8_t(&v)[S])
inline D& operator >> (uint16_t& v)
inline D& operator >> (uint32_t& v)
inline D& operator >> (mwx::null_stream&& p)

//// Example
uint8_t c;

the_twelite.stop_watchdog(); // stop watchdog
Serial.set_timeout(0xFF); // no timeout

// read out 1 byte
Serial >> c;
Serial << crlf << "char #1: [" << c << ']';

// skipping
Serial >> null_stream(3); // Read away 3 bytes
Serial << crlf << "char #2-4: skipped";

// Read 4 bytes (limited to fixed-length arrays of type uint8_t)
uint8_t buff[4];
Serial >> buff;
Serial << crlf << "char #5-8: [" << buff << "]";

Input processing.

void loop() {
  uint8_t c;
  while(Serial.available()) {
    Serial >> c;
    // Or c = Serial.read();
    
    switch(c) { ... }  // Branch processing according to the value of c
  }
}

The following is a list of types that can be read and stored.