How to use PORTD ?

Projects Programming
1

Dear all,

Currently I am trying to run two stepper Motors at the same time on my ArduinoMega. As this is not possible with stepper.h library I use digitalWrite for each pin.

To simplify my code I tried to substitute a set of digitalwirte commands with an PORTD command, but this failed.

I tried to programm simple test program using PORTD command but it does not work.
Please help me finding the problem

Thanks a lot

christian

void setup(){

Serial.begin(9600);
DDRD = B11111100;  // sets Arduino pins 3 to 7 as outputs, pin 0 as input
pinMode(3, OUTPUT);
}
void loop(){

Serial.println("low");
PORTD = B00000000; //this does not work
delay(3000);

Serial.println("high");
PORTD = B11111100;
delay(3000);

Serial.println("HIGH PIN");
digitalWrite(3, HIGH);  // this works fine
delay(3000);

Serial.println("low PIN");
digitalWrite(3, LOW);  
delay(3000);

}
2 
DDRD = B11111100;  // sets Arduino pins 3 to 7 as outputs, pin 0 as input
pinMode(3, OUTPUT);

Well on the Uno this would be pins 2 to 7, not 3 to 7, but on the Mega the port/pin mapping
is utterly different, and portD covers arduino pins 21,20,19,18 and 38.

Look at pins_arduino.h for the mega variant in the sources and you'll see something like:

const uint8_t PROGMEM digital_pin_to_port_PGM[] = {
	// PORTLIST		
	// -------------------------------------------		
	PE	, // PE 0 ** 0 ** USART0_RX	
	PE	, // PE 1 ** 1 ** USART0_TX	
	PE	, // PE 4 ** 2 ** PWM2	
	PE	, // PE 5 ** 3 ** PWM3	
	PG	, // PG 5 ** 4 ** PWM4	
	PE	, // PE 3 ** 5 ** PWM5	
	PH	, // PH 3 ** 6 ** PWM6	
	PH	, // PH 4 ** 7 ** PWM7	
	PH	, // PH 5 ** 8 ** PWM8	
	PH	, // PH 6 ** 9 ** PWM9	
	PB	, // PB 4 ** 10 ** PWM10	
	PB	, // PB 5 ** 11 ** PWM11	
	PB	, // PB 6 ** 12 ** PWM12	
	PB	, // PB 7 ** 13 ** PWM13	
	PJ	, // PJ 1 ** 14 ** USART3_TX	
	PJ	, // PJ 0 ** 15 ** USART3_RX	
	PH	, // PH 1 ** 16 ** USART2_TX	
	PH	, // PH 0 ** 17 ** USART2_RX	
	PD	, // PD 3 ** 18 ** USART1_TX	
	PD	, // PD 2 ** 19 ** USART1_RX	
	PD	, // PD 1 ** 20 ** I2C_SDA	
	PD	, // PD 0 ** 21 ** I2C_SCL	
	PA	, // PA 0 ** 22 ** D22	
	PA	, // PA 1 ** 23 ** D23	
	PA	, // PA 2 ** 24 ** D24	
	PA	, // PA 3 ** 25 ** D25	
	PA	, // PA 4 ** 26 ** D26	
	PA	, // PA 5 ** 27 ** D27	
	PA	, // PA 6 ** 28 ** D28	
	PA	, // PA 7 ** 29 ** D29	
	PC	, // PC 7 ** 30 ** D30	
	PC	, // PC 6 ** 31 ** D31	
	PC	, // PC 5 ** 32 ** D32	
	PC	, // PC 4 ** 33 ** D33	
	PC	, // PC 3 ** 34 ** D34	
	PC	, // PC 2 ** 35 ** D35	
	PC	, // PC 1 ** 36 ** D36	
	PC	, // PC 0 ** 37 ** D37	
	PD	, // PD 7 ** 38 ** D38	
	PG	, // PG 2 ** 39 ** D39	
	PG	, // PG 1 ** 40 ** D40	
	PG	, // PG 0 ** 41 ** D41	
	PL	, // PL 7 ** 42 ** D42	
	PL	, // PL 6 ** 43 ** D43	
	PL	, // PL 5 ** 44 ** D44	
	PL	, // PL 4 ** 45 ** D45	
	PL	, // PL 3 ** 46 ** D46	
	PL	, // PL 2 ** 47 ** D47	
	PL	, // PL 1 ** 48 ** D48	
	PL	, // PL 0 ** 49 ** D49	
	PB	, // PB 3 ** 50 ** SPI_MISO	
	PB	, // PB 2 ** 51 ** SPI_MOSI	
	PB	, // PB 1 ** 52 ** SPI_SCK	
	PB	, // PB 0 ** 53 ** SPI_SS	
	PF	, // PF 0 ** 54 ** A0	
	PF	, // PF 1 ** 55 ** A1	
	PF	, // PF 2 ** 56 ** A2	
	PF	, // PF 3 ** 57 ** A3	
	PF	, // PF 4 ** 58 ** A4	
	PF	, // PF 5 ** 59 ** A5	
	PF	, // PF 6 ** 60 ** A6	
	PF	, // PF 7 ** 61 ** A7	
	PK	, // PK 0 ** 62 ** A8	
	PK	, // PK 1 ** 63 ** A9	
	PK	, // PK 2 ** 64 ** A10	
	PK	, // PK 3 ** 65 ** A11	
	PK	, // PK 4 ** 66 ** A12	
	PK	, // PK 5 ** 67 ** A13	
	PK	, // PK 6 ** 68 ** A14	
	PK	, // PK 7 ** 69 ** A15	
};

So you'll see the pin mapping for low numbered arduino pins is all over the place. You would do
better to use portA, which maps to pins 22 to 29 contiguously. Several other ports map to contiguous
ranges of pins too.

1 Like
3

This explains the behavior!

Thanks a lot for this fast response!

4

Try setting up the DDRD the old fashion way.

DDRD=0XFF;
PORTD=0XFF;

the you can toggle the PORTD using( &, /).

Example code.

#include<avr/io. h>
#include<util/delay. h>

Int main(void) {

DDRD=0XFF;
PORTD=0XFF;

For(;:wink: {

PORTD&=~(1<<PD3);
_delay_ms(500);
PORTD|=(1<<PD3);

}
return 0;
}

This code toggles a led on and off every 500ms.

5

newbie_2017:
Currently I am trying to run two stepper Motors at the same time on my ArduinoMega. As this is not possible with stepper.h library I use digitalWrite for each pin.

What stepper motor drivers are you using?

Have you considered the AccelStepper or MultiStepper libraries?

The AccelStepper library can control several motors at the same time. And if you need the motors to move in a closely coordinated way then the MultiStepper library can do that.

I just use digitalWrite() in the code I have written to control 3 motors with Pololu A4988 stepper drivers.

...R
Stepper Motor Basics
Simple Stepper Code