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<concept id="GUID-5471CDD4-030E-4509-8B7C-603C9B7953B4" xml:lang="en"><title>GPIO

Technology Guide</title><shortdesc>Discusses GPIO technology as specified for implementation as a

SHAI.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-087A2FDD-8879-5944-9C0E-05ABD9FFAF50"><title>Purpose</title><p>GPIO

(General Purpose Input/Output) is a communication interface between microprocessor

components. GPIOs consist of binary inputs/outputs called pins, arranged in

groups called modules, typically of up to 32 pins in a module. GPIO is often

used to implement hardware interrupts and CPU wakeup and also to control peripherals. </p> <p>Symbian

platform defines a single static exported class <xref href="GUID-C93C53D3-2BE8-36AE-83B8-4CDB4195649B.dita"><apiname>GPIO</apiname></xref> for

device drivers to use to access the GPIO hardware on the device. The SHAI

does not provide an implementation of the class. When you implement a board

support package for device hardware with GPIO hardware, you should provide

an implementation of the class in a variant-specific component. </p> </section>

<section id="GUID-48176C53-72DC-5A2E-8124-9FA222AE91AB"><title>Key concepts</title> <p>Certain

terms have a specific meaning in the context of GPIO. </p> <dl>

<dlentry>

<dt>module</dt>

<dd><p>A group of pins which can be mapped on to a register. </p> </dd>

</dlentry>

<dlentry>

<dt>function</dt>

<dd><p>The purpose for which the pins and modules are used. GPIO is one such

purpose: serial bus line signals are an example of a different function. </p> </dd>

</dlentry>

<dlentry>

<dt>state</dt>

<dd><p>Electrical states as mapped on to mode, direction and logical state. </p> </dd>

</dlentry>

<dlentry>

<dt>configuration</dt>

<dd><p>The current configuration of all the pins on a module: their direction,

electrical and logical state, interrupt and wakeup enablement status. </p> </dd>

</dlentry>

</dl> </section>

<section id="GUID-35C041B8-F3F0-544B-A67E-0A25BE140D8B"><title>Design features</title> <p>The

Symbian platform GPIO interface reserves most decisions about design to implementers

in accordance with the platform they are writing for. However, certain design

features are implicit in the interface provided. </p> <p>These are the main

features of the Symbian platform GPIO interface: </p> <ul>

<li id="GUID-DD56DA4D-C0A7-5180-9142-81887C7538C2"><p>The interface is supplied

as a single static exported interface to be implemented as a variant specific

component. </p> </li>

<li id="GUID-B201623E-64E2-5FEF-959F-9C096F424D7E"><p>The access APIs are

specified at pin level. There are no module level APIs. </p> </li>

<li id="GUID-D8FF221C-F0EB-5F1B-886B-0F6AAC4023A9"><p>The pin IDs are to be

defined in a single enumeration with values to be determined at build time. </p> </li>

<li id="GUID-7F703C00-FE1D-5DE6-8E0E-29E4138E1060"><p>Bidirectional input/output

is not supported. </p> </li>

<li id="GUID-2CF55AD5-B98C-5207-A78F-B4C7654E677A"><p>Electrical states intermediate

between High and Low are not supported. </p> </li>

<li id="GUID-C3982CA3-04F3-58C4-B907-EE6A82FBD548"><p>It is strongly recommended

that debouncing should be implemented in software if it is not provided with

the hardware. </p> </li>

<li id="GUID-CD64A653-AB5C-575A-A3D3-0151FD8ADCF4"><p>There is limited support

for extensions to the functionality within the framework of the static interface. </p> </li>

</ul> </section>

</conbody></concept>