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-<div class="document" id="analog-to-digital-converters-adcs">
<h1 class="title">Analog-to-Digital Converters (ADCs)</h1>
<table class="docinfo" frame="void" rules="none">
<col class="docinfo-name" />
<td>Jan-Hinrich Hauer, Philip Levis, Vlado Handziski, David Gay</td></tr>
</tbody>
</table>
+<div class="document" id="analog-to-digital-converters-adcs">
<div class="note">
<p class="first admonition-title">Note</p>
<p class="last">This memo documents a part of TinyOS for the TinyOS Community, and
of this memo is unlimited. This memo is in full compliance with
<a class="citation-reference" href="#tep1" id="id1" name="id1">[TEP1]</a>.</p>
</div>
-<div class="section">
-<h1><a id="abstract" name="abstract">Abstract</a></h1>
+<div class="section" id="abstract">
+<h1><a name="abstract">Abstract</a></h1>
<p>This TEP proposes a hardware abstraction for analog-to-digital converters (ADCs)
in TinyOS 2.x, which is aligned to the three-layer Hardware Abstraction
Architecture (HAA) specified in <a class="citation-reference" href="#tep2" id="id2" name="id2">[TEP2]</a>. It describes some design principles and
documents the set of hardware-independent interfaces to an ADC.</p>
</div>
-<div class="section">
-<h1><a id="introduction" name="introduction">1. Introduction</a></h1>
+<div class="section" id="introduction">
+<h1><a name="introduction">1. Introduction</a></h1>
<p>Analog-to-digital converters (ADCs) are devices that convert analog input
signals to discrete digital output signals, typically voltage to a binary
number. The interested reader can refer to Appendix A for a brief overview of
<ul class="simple">
<li>the set of standard TinyOS interfaces for collecting ADC conversion
results and for configuring an ADC (<a class="reference" href="#interfaces">2. Interfaces</a>)</li>
-<li>guidelines on how an ADC's HAL should expose chip-specific
+<li>guidelines on how an ADC's HAL should expose chip-specific
interfaces (<a class="reference" href="#hal-guidelines">3. HAL guidelines</a>)</li>
<li>what components an ADC's HIL MUST implement (<a class="reference" href="#hil-requirements">4. HIL requirements</a>)</li>
-<li>guidelines on how the HIL should be implemented
+<li>guidelines on how the HIL should be implemented
(<a class="reference" href="#hil-guidelines">5. HIL guidelines</a>)</li>
<li>a section pointing to current implementations (<a class="reference" href="#implementation">6. Implementation</a>)</li>
</ul>
<p>This TEP ends with appendices documenting, as an example, the ADC implementation
for the TI MSP430 MCU.</p>
</div>
-<div class="section">
-<h1><a id="interfaces" name="interfaces">2. Interfaces</a></h1>
+<div class="section" id="interfaces">
+<h1><a name="interfaces">2. Interfaces</a></h1>
<p>This TEP proposes the <tt class="docutils literal"><span class="pre">AdcConfigure</span></tt> interface for ADC hardware configuration
and the <tt class="docutils literal"><span class="pre">Read</span></tt>, <tt class="docutils literal"><span class="pre">ReadStream</span></tt> and <tt class="docutils literal"><span class="pre">ReadNow</span></tt> interfaces to acquire
conversion results. The <tt class="docutils literal"><span class="pre">Read</span></tt> and <tt class="docutils literal"><span class="pre">ReadStream</span></tt> interfaces are documented
in <a class="citation-reference" href="#tep114" id="id9" name="id9">[TEP114]</a> and the <tt class="docutils literal"><span class="pre">ReadNow</span></tt> interface is documented in this TEP. A
<tt class="docutils literal"><span class="pre">Read[Now|Stream]</span></tt> interface is always provided in conjunction with a
<tt class="docutils literal"><span class="pre">AdcConfigure</span></tt> interface.</p>
-<div class="section">
-<h2><a id="interface-for-configuring-the-adc-hardware" name="interface-for-configuring-the-adc-hardware">Interface for configuring the ADC hardware</a></h2>
+<div class="section" id="interface-for-configuring-the-adc-hardware">
+<h2><a name="interface-for-configuring-the-adc-hardware">Interface for configuring the ADC hardware</a></h2>
<p>The <tt class="docutils literal"><span class="pre">AdcConfigure</span></tt> interface is defined as follows:</p>
<pre class="literal-block">
-interface AdcConfigure< config_type >
+interface AdcConfigure< config_type >
{
- async command config_type getConfiguration();
+ async command config_type getConfiguration();
}
</pre>
<p>This interface is used by the ADC stack to retrieve the hardware configuration
configuration per client - instead the ADC client can, for example, store its
configuration in program memory.</p>
</div>
-<div class="section">
-<h2><a id="interfaces-for-acquiring-conversion-results" name="interfaces-for-acquiring-conversion-results">Interfaces for acquiring conversion results</a></h2>
+<div class="section" id="interfaces-for-acquiring-conversion-results">
+<h2><a name="interfaces-for-acquiring-conversion-results">Interfaces for acquiring conversion results</a></h2>
<p>This TEP proposes to adopt the following two source-independent data
collection interfaces from <a class="citation-reference" href="#tep114" id="id10" name="id10">[TEP114]</a> for the collection of ADC conversion
results on the level of HIL:</p>
<tt class="docutils literal"><span class="pre">size_type</span></tt> parameter reflects an upper bound for the chip-specific
resolution of the conversion results - the actual resolution may be smaller
(e.g. uint16_t for a 12-bit ADC).</p>
-<div class="section">
-<h3><a id="read" name="read">Read</a></h3>
+<div class="section" id="read">
+<h3><a name="read">Read</a></h3>
<p>The <tt class="docutils literal"><span class="pre">Read</span></tt> interface can be used to sample an ADC channel once and return a
single conversion result as an uninterpreted value. The <tt class="docutils literal"><span class="pre">Read</span></tt> interface is
documented in <a class="citation-reference" href="#tep114" id="id11" name="id11">[TEP114]</a>.</p>
</div>
-<div class="section">
-<h3><a id="readstream" name="readstream">ReadStream</a></h3>
+<div class="section" id="readstream">
+<h3><a name="readstream">ReadStream</a></h3>
<p>The <tt class="docutils literal"><span class="pre">ReadStream</span></tt> interface can be used to sample an ADC channel multiple
times with a specified sampling period. The <tt class="docutils literal"><span class="pre">ReadStream</span></tt> interface is
documented in <a class="citation-reference" href="#tep114" id="id12" name="id12">[TEP114]</a> .</p>
</div>
-<div class="section">
-<h3><a id="readnow" name="readnow">ReadNow</a></h3>
+<div class="section" id="readnow">
+<h3><a name="readnow">ReadNow</a></h3>
<p>The <tt class="docutils literal"><span class="pre">ReadNow</span></tt> interface is intended for split-phase low-latency
reading of small values:</p>
<pre class="literal-block">
-interface ReadNow<val_t>
+interface ReadNow<val_t>
{
async command error_t read();
async event void readDone( error_t result, val_t val );
</div>
</div>
</div>
-<div class="section">
-<h1><a id="hal-guidelines" name="hal-guidelines">3. HAL guidelines</a></h1>
+<div class="section" id="hal-guidelines">
+<h1><a name="hal-guidelines">3. HAL guidelines</a></h1>
<p>As explained in <a class="reference" href="#introduction">1. Introduction</a> the HAL exposes the full capabilities of the
ADC hardware. Therefore only chip- and platform-dependent clients can wire to
the HAL. Although the HAL is chip-specific, both, in terms of implementation
and representation, its design should follow the guidelines described in this
section to facilitate the mapping to the HIL representation. Appendix B shows
the signature of the HAL for the MSP430.</p>
-<div class="section">
-<h2><a id="resource-reservation" name="resource-reservation">Resource reservation</a></h2>
+<div class="section" id="resource-reservation">
+<h2><a name="resource-reservation">Resource reservation</a></h2>
<p>As the ADC hardware is a shared resource that is usually multiplexed between
several clients some form of access arbitration is necessary. The HAL should
therefore provide a parameterized <tt class="docutils literal"><span class="pre">Resource</span></tt> interface, instantiate a
all platforms the standard round robin arbiter is recommended. Resource
arbiters and the <tt class="docutils literal"><span class="pre">Resource</span></tt> interface are the topic of <a class="citation-reference" href="#tep108" id="id15" name="id15">[TEP108]</a>.</p>
</div>
-<div class="section">
-<h2><a id="configuration-and-sampling" name="configuration-and-sampling">Configuration and sampling</a></h2>
+<div class="section" id="configuration-and-sampling">
+<h2><a name="configuration-and-sampling">Configuration and sampling</a></h2>
<p>As the ADC hardware is a shared resource the HAL should support hardware
configuration and sampling per client (although per-port configuration is
possible, it is not recommended, because it forces all clients to use the same
it after the return of the respective command. Appendix B shows the HAL
interfaces for the MSP430.</p>
</div>
-<div class="section">
-<h2><a id="hal-virtualization" name="hal-virtualization">HAL virtualization</a></h2>
+<div class="section" id="hal-virtualization">
+<h2><a name="hal-virtualization">HAL virtualization</a></h2>
<p>In order to hide wiring complexities and/or export only a subset of all ADC
functions generic ADC wrapper components may be provided on the level of HAL.
Such components can also be used to ensure that a sampling interface is always
client ID if this is required by the HAL implementation.</p>
</div>
</div>
-<div class="section">
-<h1><a id="hil-requirements" name="hil-requirements">4. HIL requirements</a></h1>
+<div class="section" id="hil-requirements">
+<h1><a name="hil-requirements">4. HIL requirements</a></h1>
<p>The following generic components MUST be provided on all platforms that have an
ADC:</p>
<pre class="literal-block">
-AdcReadClientC
-AdcReadNowClientC
-AdcReadStreamClientC
+AdcReadClientC
+AdcReadNowClientC
+AdcReadStreamClientC
</pre>
<p>These components provide virtualized access to the HIL of an ADC. They are
instantiated by an ADC client and provide/use the four interfaces described in
platform (the question of how to deal with multiple devices of the same class
is a general one in TinyOS 2.x). Appendix C shows the <tt class="docutils literal"><span class="pre">AdcReadClientC</span></tt> for
the MSP430.</p>
-<div class="section">
-<h2><a id="adcreadclientc" name="adcreadclientc">AdcReadClientC</a></h2>
+<div class="section" id="adcreadclientc">
+<h2><a name="adcreadclientc">AdcReadClientC</a></h2>
<pre class="literal-block">
generic configuration AdcReadClientC() {
provides {
placeholders and will be instantiated by the respective HIL implementation (for
an example, see the AdcReadClientC for the MSP430 in Appendix C).</p>
</div>
-<div class="section">
-<h2><a id="adcreadnowclientc" name="adcreadnowclientc">AdcReadNowClientC</a></h2>
+<div class="section" id="adcreadnowclientc">
+<h2><a name="adcreadnowclientc">AdcReadNowClientC</a></h2>
<pre class="literal-block">
generic configuration AdcReadNowClientC() {
provides {
instantiated by the respective HIL implementation (for an example how this is
done for the AdcReadClientC see Appendix C).</p>
</div>
-<div class="section">
-<h2><a id="adcreadstreamclientc" name="adcreadstreamclientc">AdcReadStreamClientC</a></h2>
+<div class="section" id="adcreadstreamclientc">
+<h2><a name="adcreadstreamclientc">AdcReadStreamClientC</a></h2>
<pre class="literal-block">
generic configuration AdcReadStreamClientC() {
provides {
this is done for the AdcReadClientC see Appendix C).</p>
</div>
</div>
-<div class="section">
-<h1><a id="hil-guidelines" name="hil-guidelines">5. HIL guidelines</a></h1>
+<div class="section" id="hil-guidelines">
+<h1><a name="hil-guidelines">5. HIL guidelines</a></h1>
<p>The HIL implementation of an ADC stack has two main tasks: it translates a
<tt class="docutils literal"><span class="pre">Read</span></tt>, <tt class="docutils literal"><span class="pre">ReadNow</span></tt> or <tt class="docutils literal"><span class="pre">ReadStream</span></tt> request to a chip-specific HAL sampling
command and it abstracts from the <tt class="docutils literal"><span class="pre">Resource</span></tt> interface (the latter only for
check can also be done in the HAL implementation). Once the HIL is signalled
the conversion result(s) it forwards it to the respective <tt class="docutils literal"><span class="pre">ReadNow</span></tt> client.</p>
</div>
-<div class="section">
-<h1><a id="implementation" name="implementation">6. Implementation</a></h1>
-<div class="section">
-<h2><a id="testadc-application" name="testadc-application">TestAdc application</a></h2>
+<div class="section" id="implementation">
+<h1><a name="implementation">6. Implementation</a></h1>
+<div class="section" id="testadc-application">
+<h2><a name="testadc-application">TestAdc application</a></h2>
<p>An ADC HIL test application can be found in <tt class="docutils literal"><span class="pre">tinyos-2.x/apps/tests/TestAdc</span></tt>.
Note that this application instantiates generic DemoSensorC, DemoSensorStreamC
and DemoSensorNowC components (see <a class="citation-reference" href="#tep114" id="id19" name="id19">[TEP114]</a>) and assumes that these components
are actually wired to an ADC HIL. Please refer to
<tt class="docutils literal"><span class="pre">tinyos-2.x/apps/tests/TestAdc/README.txt</span></tt> for more information.</p>
</div>
-<div class="section">
-<h2><a id="haa-on-the-msp430-and-atmega-128" name="haa-on-the-msp430-and-atmega-128">HAA on the MSP430 and Atmega 128</a></h2>
+<div class="section" id="haa-on-the-msp430-and-atmega-128">
+<h2><a name="haa-on-the-msp430-and-atmega-128">HAA on the MSP430 and Atmega 128</a></h2>
<p>The implementation of the ADC12 stack on the MSP430 can be found in
<tt class="docutils literal"><span class="pre">tinyos-2.x/tos/chips/msp430/adc12</span></tt>:</p>
<blockquote>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">HplAtm128AdcC.nc</span></tt> is the HPL implementation</li>
<li><tt class="docutils literal"><span class="pre">Atm128AdcP.nc</span></tt> is the HAL implementation</li>
-<li><tt class="docutils literal"><span class="pre">AdcP.nc</span></tt>, <tt class="docutils literal"><span class="pre">WireAdcP.nc</span></tt> and the library components for arbitrating
+<li><tt class="docutils literal"><span class="pre">AdcP.nc</span></tt>, <tt class="docutils literal"><span class="pre">WireAdcP.nc</span></tt> and the library components for arbitrating
'Read', 'ReadNow' and 'ReadStream', <tt class="docutils literal"><span class="pre">ArbitratedReadC</span></tt> and
<tt class="docutils literal"><span class="pre">ArbitratedReadStreamC</span></tt> (in <tt class="docutils literal"><span class="pre">tinyos-2.x/tos/system</span></tt>), realize
the HIL</li>
</blockquote>
</div>
</div>
-<div class="section">
-<h1><a id="appendix-a-hardware-differences-between-platforms" name="appendix-a-hardware-differences-between-platforms">Appendix A: Hardware differences between platforms</a></h1>
+<div class="section" id="appendix-a-hardware-differences-between-platforms">
+<h1><a name="appendix-a-hardware-differences-between-platforms">Appendix A: Hardware differences between platforms</a></h1>
<p>The following table compares the characteristics of two microcontrollers
commonly used in TinyOS platforms:</p>
<table border="1" class="docutils">
<col width="32%" />
</colgroup>
<thead valign="bottom">
-<tr><th class="head"> </th>
-<th class="head">Atmel Atmega 128</th>
-<th class="head">TI MSP430 ADC12</th>
+<tr><th> </th>
+<th>Atmel Atmega 128</th>
+<th>TI MSP430 ADC12</th>
</tr>
</thead>
<tbody valign="top">
</tbody>
</table>
</div>
-<div class="section">
-<h1><a id="appendix-b-a-hal-representation-msp430-adc12" name="appendix-b-a-hal-representation-msp430-adc12">Appendix B: a HAL representation: MSP430 ADC12</a></h1>
+<div class="section" id="appendix-b-a-hal-representation-msp430-adc12">
+<h1><a name="appendix-b-a-hal-representation-msp430-adc12">Appendix B: a HAL representation: MSP430 ADC12</a></h1>
<p>This section shows the HAL signature for the ADC12 of the TI MSP430 MCU. It
reflects the four MSP430 ADC12 conversion modes as it lets a client sample an
ADC channel once ("Single-channel-single-conversion") or repeatedly
<tt class="docutils literal"><span class="pre">DMAExtension</span></tt> interface is used to reset the state machine when the DMA is
responsible for data transfer (managed in an exterior component):</p>
<pre class="literal-block">
-configuration Msp430Adc12P
-{
+configuration Msp430Adc12P
+{
provides {
- interface Resource[uint8_t id];
- interface Msp430Adc12SingleChannel as SingleChannel[uint8_t id];
+ interface Resource[uint8_t id];
+ interface Msp430Adc12SingleChannel as SingleChannel[uint8_t id];
interface AsyncStdControl as DMAExtension[uint8_t id];
}
}
-interface Msp430Adc12SingleChannel
-{
+interface Msp430Adc12SingleChannel
+{
async command error_t configureSingle(const msp430adc12_channel_config_t *config);
async command error_t configureSingleRepeat(const msp430adc12_channel_config_t *config, uint16_t jiffies);
async command error_t configureMultiple( const msp430adc12_channel_config_t *config, uint16_t buffer[], uint16_t numSamples, uint16_t jiffies);
async command error_t configureMultipleRepeat(const msp430adc12_channel_config_t *config, uint16_t buffer[], uint8_t numSamples, uint16_t jiffies);
async command error_t getData();
async event error_t singleDataReady(uint16_t data);
- async event uint16_t* multipleDataReady(uint16_t buffer[], uint16_t numSamples);
+ async event uint16_t* multipleDataReady(uint16_t buffer[], uint16_t numSamples);
}
-typedef struct
-{
- unsigned int inch: 4; // input channel
- unsigned int sref: 3; // reference voltage
- unsigned int ref2_5v: 1; // reference voltage level
- unsigned int adc12ssel: 2; // clock source sample-hold-time
- unsigned int adc12div: 3; // clock divider sample-hold-time
+typedef struct
+{
+ unsigned int inch: 4; // input channel
+ unsigned int sref: 3; // reference voltage
+ unsigned int ref2_5v: 1; // reference voltage level
+ unsigned int adc12ssel: 2; // clock source sample-hold-time
+ unsigned int adc12div: 3; // clock divider sample-hold-time
unsigned int sht: 4; // sample-hold-time
- unsigned int sampcon_ssel: 2; // clock source sampcon signal
+ unsigned int sampcon_ssel: 2; // clock source sampcon signal
unsigned int sampcon_id: 2; // clock divider sampcon signal
} msp430adc12_channel_config_t;
</pre>
</div>
-<div class="section">
-<h1><a id="appendix-c-a-hil-representation-msp430-adc12" name="appendix-c-a-hil-representation-msp430-adc12">Appendix C: a HIL representation: MSP430 ADC12</a></h1>
+<div class="section" id="appendix-c-a-hil-representation-msp430-adc12">
+<h1><a name="appendix-c-a-hil-representation-msp430-adc12">Appendix C: a HIL representation: MSP430 ADC12</a></h1>
<p>The signature of the AdcReadClientC component for the MSP430 ADC12 is as
follows:</p>
<pre class="literal-block">
projects / tinyos-2.x.git / blobdiff