PortIn

Table of Contents

  1. Hello World!
  2. API
  3. Interface
  4. Related

The PortIn interface is used to read an underlying GPIO port as one value. This is much faster than BusIn as you can read a port in one go, but much less flexible as you are constrained by the port and bit layout of the underlying GPIO ports.

A mask can be supplied so only certain bits of a port are used, allowing other bits to be used for other interfaces.

Hello World!

» Import this program
PortIn_HelloWorld - main.cpp

// Switch on an LED if any of mbed pins 21-26 is high
 
#include "mbed.h"
 
PortIn     p(Port2, 0x0000003F);   // p21-p26
DigitalOut ind(LED4);
 
int main() {
    while(1) {
        int pins = p.read();
        if(pins) {
            ind = 1;
        } else {
            ind = 0;
        }
    }
}

API

» Import latest build into a program
mbed - PortIn Class Reference

Public Member Functions

  PortIn (PortName port, int mask=0xFFFFFFFF)
  Create an PortIn , connected to the specified port.
int  read ()
  Read the value currently output on the port.
void  mode (PinMode mode)
  Set the input pin mode.
  operator int ()
  A shorthand for read()

Interface

The PortIn Interface can use any pin with a blue label, as long as all the pins used are in the same GPIO port

/media/uploads/chris/pinout-thumbnails.jpg
See the Pinout page for more details


Ask a question
Last modified 22 Feb 2013, by user Emilio Monti. 8 comments

8 comments:

user LFY R
16 Nov 2010

In the above example, how do you know port2 is a group of P21-P26 ?

user Christian Lerche
16 Nov 2010

Hi LFY

http://mbed.org/users/Lerche/notebook/lpc1768-pin-functions/ In the above link, you'll find a table of the pins of LPC1768, where 21-26 all are on port2.

Lerche

user Arasch Lagies
18 Nov 2010

So this means e.g. that the mbed pin p11 to p18 are all Port 0 ?? How would you put mbed pin p20 to p27 (mixture of Port0, Port1 and Port2) together to use the input values as one hex number?

user Simon Ford
18 Nov 2010

Hi Arasch,

Take a look at BusIn; that gives you total flexibility of what pins go where (at the cost of performance; it basically has to read each pin individually, but in your code you only need to read one value)

user Arasch Lagies
19 Nov 2010

With the pin functions table I get for the pin sequence p11 to p18 the hex number 0x7878000, so the call here would be PortIn p(Port0, 0x7878000). Is this right? Somehow this does not seem to work.

user - tunkki
01 Jan 2011

user Arasch Lagies wrote:

With the pin functions table I get for the pin sequence p11 to p18 the hex number 0x7878000, so the call here would be PortIn p(Port0, 0x7878000). Is this right? Somehow this does not seem to work.

Have you tried: p(Port0,0x0007F800) The thing is that because you already call Port0, you have to mask inside that port. Not sure, but could be this way.

user - tunkki
02 Jan 2011

user - tunkki wrote:

user Arasch Lagies wrote:

With the pin functions table I get for the pin sequence p11 to p18 the hex number 0x7878000, so the call here would be PortIn p(Port0, 0x7878000). Is this right? Somehow this does not seem to work.

Have you tried: p(Port0,0x0007F800) The thing is that because you already call Port0, you have to mask inside that port. Not sure, but could be this way.

Actually you should have (Port0, 0x07878000); p11-p18(p0.16-18, p0.23-26) port 0 == 0000 0111 1000 0111 1000 0000 0000 0000

user Arasch Lagies
10 Jun 2011

user - tunkki wrote:

Actually you should have (Port0, 0x07878000); p11-p18(p0.16-18, p0.23-26) port 0 == 0000 0111 1000 0111 1000 0000 0000 0000

Thanks tunkki, (Port0, 0x07878000); p11-p18(p0.15-18, p0.23-26) for port 0 == 0000 0111 1000 0111 1000 0000 0000 0000 works.

Now I only have to take care that the pin sequence using the mask is different to the mbed pins.

I need also a second 8bit connection. One possibility was to use

p9 -> P0.0

p10 -> P0.1

p30 -> P0.4

p29 -> P0.5

P8 -> P0.6

p7 -> P0.7

p6 -> P0.8

p5 -> P0.9

This is port0 == 0000 0000 0000 0000 0000 0011 1111 0011

which is (Port0, 0x000003F3)

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