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<head><title>CONFIGPIN</title>
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<h1 class="code">CONFIGPIN</h1>
<div class="ImagePlusCaption">
<div class="Col2">
<p>
<img src="../../graphics/pgm_icon2px.gif" border="0" alt="BS2px icon" title="BS2px icon" />
</p>
</div>
<p style="text-align: right;"><a href="../ExampleTopics/ConfigpinEx.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">CONFIGPIN Example</a>
</p>
<p>&#160;</p>
</div>
<p class="clear">&#160;</p>
<p>&#160;</p>
<p class="PlainText">Syntax: <span class="keyword_in_text">CONFIGPIN</span> <![CDATA[ ]]><i>Mode</i>, <i>PinMask</i></p>
<h2>Function</h2>
<p class="PlainText">Configure special properties of I/O pins.
</p>
<ul>
<li value="1"><b><i>Mode</i></b>&#160; is a variable/constant/expression (0 – 3), or one
of four predefined symbols, that specifies the I/O pin property to configure:
Schmitt Trigger, Logic Threshold, Pull-up Resistor or Output Direction. See
table below for an explanation of <i>Mode</i> values.</li>
<li value="2"><b><i>PinMask</i></b>&#160; is a variable/constant/expression (1 – 65535)
that indicates how <i>Mode</i> is applied to I/O pins. Each bit of
<i>PinMask</i> corresponds to an individual I/O pin. A high bit (1) enables
the <i>Mode</i> and a low bit (0) disables the <i>Mode</i> on the
corresponding I/O pin.</li>
</ul>
<h2>Quick Facts<br /></h2>
<table width="100%" cellpadding="4" cellspacing="0" border="1">
<tr bgcolor="#CFCFCF">
<td width="80" align="center">&#160;</td>
<td width="80%%" align="center">BS2px</td>
</tr>
<tr>
<td align="center" rowspan="4" bgcolor="#CFCFCF"><i>Mode</i> Values</td>
<td>0 (or SCHMITT): Schmitt Trigger</td>
</tr>
<tr>
<td>1 (or THRESHOLD): Logic Threshold</td>
</tr>
<tr>
<td>2 (or PULLUP): Pull-up Resistor</td>
</tr>
<tr>
<td>3 (or DIRECTION): Output Direction</td>
</tr>
<tr>
<td align="center" bgcolor="#CFCFCF">Related Commands</td>
<td align="center" colspan="1">
<p colspan="1" align="center"><a href="INPUT.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">INPUT</a>, <a href="OUTPUT.htm" target="" title="" alt="" class="MCXref_0" xrefformat="{paratext}">OUTPUT</a></p>
</td>
</tr>
</table>
<h2>Explanation</h2>
<p class="PlainText">The <span class="keyword_in_text">CONFIGPIN</span> command enables or disables special I/O pin properties
on all 16 I/O pins at once. There are four properties, or modes, available:
Schmitt Trigger, Logic Threshold, Pull-up Resistor, and Output Direction.
Each I/O pin on the BS2px contains special hardware dedicated to each of
these properties.</p>
<p class="PlainText">By default, all BASIC Stamp I/O pins are set to inputs. Enabling the
Output Direction mode sets an I/O pin’s direction to output. Disabling
the Output Direction mode sets an I/O pin’s direction to input. This has
the same effect as using the <span class="keyword_in_text">OUTPUT</span> or <span class="keyword_in_text">INPUT</span> commands, or the
DIRx = # assignment statement to configure I/O pin directions. The
following is an example of the <span class="keyword_in_text">CONFIGPIN</span> command using the Output
Direction mode:</p><pre class="BScode" xml:space="preserve">
CONFIGPIN DIRECTION, %0000000100010011
</pre>
<p class="PlainText">Every high bit (1) in the <i>PinMask</i> argument enables the output direction
for the corresponding I/O pin while every low bit (0) disables the output
direction. In the above example, I/O pins 8, 4, 1, and 0 are set to the
output direction and all other I/O pins are set to the input direction. This
is similar to the following statement:</p><pre class="BScode" xml:space="preserve">
DIRS = %0000000100010011
</pre>
<p class="PlainText">Pull-up resistors are commonly used in circuitry where a component, such
as a button, provides an open/drain signal; the signal is either floating
(open) or is driven to ground (drain). Since the BASIC Stamp input pins
must always be connected to either 5 volts or ground (0 volts) in order to
read a reliable logic state with them, a pull-up resistor is required on
circuitry, such as the button circuit mentioned above, so that the signal is
never left floating (electrically disconnected).</p>
<p class="PlainText">The following example enables internal pull-up resistors on I/O pins 15,
12, 6, and 3, and disables internal pull-up resistors on all other I/O pins:</p><pre class="BScode" xml:space="preserve">
CONFIGPIN PULLUP, %1001000001001000
</pre>
<p class="PlainText">Note that the internal pull-up resistors are intentionally weak, about 20
kΩ. Additionally, the internal pull-up resistors can be activated for all
pins, regardless of pin direction, but really matter only when the
associated pin is set to input mode.</p>
<p class="PlainText">An input pin’s logic threshold determines the voltage levels that are
interpreted as logic high (1) and logic low (0). Most microcontrollers, and
other integrated circuits use one of two types of logic threshold: TTL Level
or CMOS Level. The BASIC Stamp I/O pins are, by default, configured for TTL
level logic thresholds. The figure below is an illustration of the difference
between TTL and CMOS logic levels.</p>
<table border="0">
<tr>
<td>
<img src="../../graphics/level_ttl.gif" border="0">
</img>
</td>
<td>&#160; &#160; &#160; &#160; &#160;</td>
<td>
<img src="../../graphics/level_cmos.gif" border="0">
</img>
</td>
</tr>
<tr align="center">
<td><b>TTL Logic Level</b>
</td>
<td>&#160; &#160;</td>
<td><b>CMOS Logic Level</b>
</td>
</tr>
</table>
<p class="PlainText">&#160;</p>
<p class="PlainText">The logic threshold for TTL is 1.4 volts; a voltage below 1.4 is considered
to be a logic 0 while a voltage above 1.4 is considered to be a logic 1. The
logic threshold for CMOS is 50% of Vdd; a voltage below ½ Vdd is
considered a logic 0 while a voltage above ½ Vdd is considered a logic 1.</p>
<p class="PlainText">For the <span class="keyword_in_text">CONFIGPIN</span> command's THRESHOLD mode, a high bit (1) in the
<i>PinMask</i> argument sets the corresponding I/O pin to CMOS threshold
level, and a low bit sets it to a TTL threshold level. The following example
sets CMOS threshold level on I/O pins 3, 2, 1, and 0, and TTL threshold
level on all other I/O pins.</p><pre class="BScode" xml:space="preserve">
CONFIGPIN THRESHOLD, %0000000000001111
</pre>
<p class="PlainText">The threshold level can be set for all pins, regardless of pin direction, but
really matters only when the associated pin is set to input mode.</p>
<p class="PlainText">Normally, if a signal on an input pin is somewhat noisy (the voltage level
randomly rises and falls beyond the logic threshold boundary) then
reading that pin’s input value will result in spurious highs and lows (1s
and 0s). Schmitt Triggers are circuits that make inputs more steady and
reliable by adding a region of hysteresis around the logic threshold that
the signal must completely traverse before the logic level is interpreted as
being changed. By default BASIC Stamp I/O pins are set to normal input
mode, but the BS2px can be configured for Schmitt Trigger mode as well.
The figure below illustrates Schmitt Trigger characteristics.</p>
<table border="0">
<tr>
<td>
<img src="../../graphics/level_schmitt.gif" border="0">
</img>
</td>
</tr>
</table>
<p class="PlainText">In Schmitt Trigger mode, the threshold for a logic 0 is approximately 15%
of Vdd and the threshold for a logic 1 is approximately 85% of Vdd. The
input pin defaults to an unknown state until the initial voltage crosses a
logic 0 or logic 1 boundary. Thereafter, the voltage must cross above 85%
of Vdd to be interpreted as a logic 1 and must cross below 15% of Vdd to
be interpreted as a logic 0. If the voltage transitions somewhere between
the two thresholds, the interpreted logic state remains the same as the
previous state.</p>
<p class="PlainText">For the <span class="keyword_in_text">CONFIGPIN</span> command’s SCHMITT mode, a high bit (1) in the
<i>PinMask</i> argument enables the Schmitt Trigger on the corresponding I/O
pin and a low bit (0) disables the Schmitt Trigger. The following example
sets Schmitt Triggers on I/O pins 7, 6, 5, and 4, and sets all other I/O pins
to normal mode.</p><pre class="BScode" xml:space="preserve">
CONFIGPIN SCHMITT, %0000000011110000
</pre>
<p class="PlainText">Schmitt Trigger mode can be activated for all pins, regardless of pin
direction, but really matters only when the associated pin is set to input
mode.</p>
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<p style="text-align: right;"><span class="ContactInfoProjectName">BASIC Stamp Help</span> <![CDATA[ ]]><span class="ContactInfoVersion#">Version 2.5.4</span> <![CDATA[ ]]></p>
<p style="text-align: right;">Copyright ©&#160;<span class="ContactInfoCompanyName">Parallax Inc.</span></p>
<p style="text-align: right;"><span class="SystemShortDate">8/8/2012</span>
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