Sending LCD commands to a slave micro

Question

I need to split up code which I've already developed for one micro into two different Arduinos connected by serial. The "remote" micro is directly connected to a 20x4 character LCD and the main micro will be sending it a command set to print, move cursor, etc.

My plan was to make functions that used existing code such as lcd.print("This or that"); to replace the lcd library on the main micro and send command bytes and data bytes up to the remote micro. Seems pretty straightforward.

Then I discovered that apparently lcd.print cannot be a function name. Fine, so I changed it to lcd_print(). So far, so good. But in the existing library, lcd.print accepts strings, bytes, just about anything any length. For example: lcd_print("any string of any length"); lcd_print(a_2d_array [x] [y]); lcd_print(this_byte); lcd_print(this_integer);

Now it's getting over my head. I know I can painstakingly turn a single function into many different functions, but wouldn't it be nice to replicate the functionality of the Arduino LCD library with a single command:

lcd.print();

Then all I have to do is create the function and keep the existing code and send the bytes up to the slave micro. Wouldn't that be nice! I appreciate any thoughts. Thanks.

Answer 1

Just inherit Print class and implement virtual size_t write(uint8_t); and you can use all kinds of print/println that Print implements. See Print Class @arduino.cc.

It implements these methods for you:

size_t print(const __FlashStringHelper *);
size_t print(const String &);
size_t print(const char[]);
size_t print(char);
size_t print(unsigned char, int = DEC);
size_t print(int, int = DEC);
size_t print(unsigned int, int = DEC);
size_t print(long, int = DEC);
size_t print(unsigned long, int = DEC);
size_t print(double, int = 2);
size_t print(const Printable&);

size_t println(const __FlashStringHelper *);
size_t println(const String &s);
size_t println(const char[]);
size_t println(char);
size_t println(unsigned char, int = DEC);
size_t println(int, int = DEC);
size_t println(unsigned int, int = DEC);
size_t println(long, int = DEC);
size_t println(unsigned long, int = DEC);
size_t println(double, int = 2);
size_t println(const Printable&);
size_t println(void);

However you have to implement 2D array print if you really need this, I don't see why do you need it but whatever (you can print each line separately). It just saves you time with implementing everything else.

And for std::ostream like approach I like this (works with anything inherited from Print class):

template <class T> inline Print & operator<<(Print & p, const T & val) {
  p.print(val);
  return p;
}

// ...

void loop() {
  float variableA = 221.23;
  String variableB = "Some string";
  Serial << F("flash string to save some ram: ") << variableA << F(" / ") << variableB << "\n";
}

Then you can implement some commands interface.