Writing multiple pins seems like a good idea, at least in the abstract. There are cases where dedicating an entire 8-bit port to a device makes sense but this is not write multiple pins.
I have written a lot of bit-bang code for SPI, I2C, and various devices. When I get to real hardware, my abstract write multiple ideas never seem to help.
Does anyone have a situation with real hardware where an existing implementation would be improved by write multiple with three or four pins. The pins must be restricted to a single port.
The best example I have is something like an LCD display. In this case the restriction that all pins are on the same port is too severe. The library LiquidCrystal allows any pins and that doesn't add much complication. Here are the byte and nibble write functions.
void LiquidCrystal::write4bits(uint8_t value) {
for (int i = 0; i < 4; i++) {
pinMode(_data_pins[i], OUTPUT);
digitalWrite(_data_pins[i], (value >> i) & 0x01);
}
pulseEnable();
}
void LiquidCrystal::write8bits(uint8_t value) {
for (int i = 0; i < 8; i++) {
pinMode(_data_pins[i], OUTPUT);
digitalWrite(_data_pins[i], (value >> i) & 0x01);
}
pulseEnable();
}
Note this code has pinMode in the write function. LCD displays can be written or read so your write multiple should also support read.
It's the details of real complex devices that seems to kill the advantages of a library for accessing multiple pins.