OO Digital Pin class: single class or separate in and out classes

In the pic world microchip provides helper structs defining each pin as a bit field

#define LATA LATA
extern volatile uint16_t LATA __attribute__((__sfr__));
typedef struct tagLATABITS {
  uint16_t LATA0:1;
  uint16_t LATA1:1;
  uint16_t LATA2:1;
  uint16_t LATA3:1;
  uint16_t LATA4:1;
} LATABITS;
extern volatile LATABITS LATAbits __attribute__((__sfr__));


#define led LATAbits.LATA0

led = 1;
led ~= led; // etc....

Not c++, but simple.

In the pic world microchip provides helper structs defining each pin as a bit field

#define LATA LATA
extern volatile uint16_t LATA __attribute__((__sfr__));
typedef struct tagLATABITS {
  uint16_t LATA0:1;
  uint16_t LATA1:1;
  uint16_t LATA2:1;
  uint16_t LATA3:1;
  uint16_t LATA4:1;
} LATABITS;
extern volatile LATABITS LATAbits __attribute__((__sfr__));


#define led LATAbits.LATA0

led = 1;
led ~= led; // etc....

Not c++, but simple.

That's what I'm working with - and where my examples came from!  These could be OO-ified (I'm full of new English words today.)

The controller I'm using does the same:

Setting a bit: PORTH.PODR.BIT.B2 = 0

(the construct is a set of structs and unions that 'll get you up to bit level. Same as the microchip.)

The thing is that it has different paths for reading and writing 

Reading a bit: PORTH.PIDR.BIT.B2 

I could solve this by setting:

#define led_read = PORTH.PIDR.BIT.B2 
#define led_write = PORTH.PODR.BIT.B2 

led_write = 1;
led_write ~= led_read; // etc

scottiebabe said:

Not c++, but simple.

I took this (maybe most) simple example explicitly, because it's constrained enough to get a brainstorm going. 

Is it like a PIC?

Microchip hide that read/write distinction if you want:

PORTA = 0xFF actually redirects (compiles) to LATA=0xFF under the covers, so you can read and write through PORTA.  I'm more explicit in my code to avoid that confusion so it ends up similar to the code you have where the read uses PORTA or RA0 (for a specific bit) and write uses LATA or LATA0 (for a specific bit). 

The Renesas syntax is a lot more long winded so I'm not surprised you are looking to encapsulate it some way.

It goes further as well (as you probably know) because each of the bits are identifiable directly:

#define led LATA0

led = 1;

etc

Yes! Thanks for reminding me, sometimes there is an underscore in front

Lots of others have written long winded explanations on reading from the write latch versus pin state. When using an io pin as an output its customary to reference pin reads to the output drive latch. Capacitive loading on the IO pin can delay when the pin input buffer matches the output latches write value.

That's interesting as the datasheet doesn't reference that.  It limits itself to "Writes to PORTx are actually written to corresponding LATx register.  Reads from PORTx register is return of actual I/O pin values" and also "A write operation to the LATx register has the same effect as a write to the corresponding PORTx register.  A read of the LATx register reads of the values held in the I/O Port latches, while a read of the PORTx register reads the actual I/O pin value".  No mention of a potential mismatch but it's good to know, thanks.

I can't remember where I read about it first, but one example

Credit to them. ww1.microchip.com/.../39711b.pdf

The type of controller and its complexity was not the reason why I'm playing with this. It could have been any other. I'm just using the one the one that I currently have at hand. Could have been a Pico, or something else.

I'm trying to do some brain flexing to find a good level of abstraction, and talk about ways of doing it with the fellow forum members. And to keep my c++/oo abstraction muscles trained.