Making all the port as output

Robotics and electronics discussion Software and microcontrollers
1

Hay
I need to define the whole pot as output. Is there a way to do that without defining each port separately?
Thanks
Arbel

2

Hi Arbel,

You might want to be careful when setting all your pins to outputs because it can lead to accidental shorts.

You didn’t say what microcontroller you are using, so, since a lot of people around here use AVRs, I will tell you how to do it on the AVR. If you want to make port D all outputs you want to set all the bits in the D data direction register like this (in C):

DDRD = 0xFF;

If you need help with another microcontroller, you should post which one you are using and what language you are programming in.

- Ryan

3

I am using babyO Its atmega168. what do you meen shrtcuts? is I need to light up 7 leds at the same time (in a 7 segment number display) is there a problem doing that?
Arbel

4

When I said, “shorts,” I meant short circuits, not short cuts. On way short circuits can happen is when you accidentally connect a source output pin to a sink output pin. This creates a path from Vcc to GND that has very little resistance, meaning a high current will flow through the IO pins. The pins can not handle very much current (take a look at the atmega168 datasheet on Atmel’s website) and will probably break if they are part of a short circuit.

Using the Mega168’s IO pins to power 7 LEDs should be okay, as long as the LEDs have the right size resistor in series with them.

- Ryan

5

Hello.

I’d like to add that you do not need to set all the pins to outputs at the same time. You could do it one pin at a time and all the LEDs would seem to turn on simultaneously since it only takes a few hundred nanoseconds to execute an instruction on the Baby Orangutan.

- Ben