Parallel data transmission/reception with Arduino Nano

Projects General Guidance
1

I am working on a project using a Nano to program an AD9850 DDS module. In all the research I have conducted regarding this combination, communication is done serially. Research on parallel communication (using pins D0-D7) reminds the reader that Arduinos use D0 and D1 for serial communication with the serial monitor and the computer hosting the Arduino IDE, and that co-opting D0/D1 for parallel communication (through PORTD) runs the risk of disabling serial communication.

However, the Serial library includes both Serial.begin, and Serial.end methods. If I were to conduct parallel communication through PORTD within a bracket of Serial.end/Serial.begin, would I be running the same risk.

That is:
//
void loop() {
...
Serial.end() //Terminate serial communication

// Begin parallel communication through PORTD
...
//End of parallel communication

Serial.begin(9600) //Re-establish serial communication
...
}

Another way of asking this question is: Does the Serial.begin method make any assumptions regarding the state of pins D0/D1, or does it reset those pins to a known state before proceeding with communication.

2

What is the demand for communication speed, bytes per second?
Using a serial transmission into a shift register that after the last bit shows a parallell byte could be one way.

3

Keep in mind that there is no need to use sequential arduino pin numbers.
In fact for direct port access you’ll probably find you’re better off using direct port access.

One place you may look for inspiration is 8-bit parallel LCD drivers.

Equally, transmitting the eight bits in parallel is relatively easy. Receiving and reconstructing that data synchronously is a little more challenging.

Serial is definitely the way to go if available... SPI, I2C etc.