Came across this thread again today and dived into it. Came up with the following code.
As I lent my logic analyser to a friend so I could not check it yet,
so warning, highly experimental code, use at own risk
Goal: this code is to merge the masks of the bits to set simultaneously.
to be included in wiring_digital.c
void multiDigitalWrite(uint8_t *pins, uint8_t size, uint8_t val)
{
// pins_arduino.h/c
#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
const int numberOfPorts = 12;
uint8_t bits[numberOfPorts] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
#else // 328 - 168
const int numberOfPorts = 5;
uint8_t bits[numberOfPorts] = { 0, 0, 0, 0, 0 };
#endif
for (uint8_t i = 0; i < size; i++)
{
uint8_t p = digitalPinToPort(pins[i]);
if (p == NOT_A_PIN) continue;
bits[p] | = digitalPinToBitMask(pins[i]);
uint8_t timer = digitalPinToTimer(pins[i]);
if (timer != NOT_ON_TIMER) turnOffPWM(timer);
}
volatile uint8_t *out;
for (int p = 0; p < numberOfPorts; p++)
{
if (bits[p] == 0) continue; // no bits => skip port
out = portOutputRegister(p);
uint8_t oldSREG = SREG;
cli();
if (val == LOW)
{
*out &= ~bits[p];
} else {
*out |= bits[p];
}
SREG = oldSREG;
}
}