[Tinyos-2.0wg] Meeting: September 6
Philip Levis
pal at cs.stanford.edu
Tue Sep 5 22:02:04 PDT 2006
Agenda:
Generic components in TinyOS 1.x (resuscitation of 1.2 WG?)
TEP 101 (review comments from Jack)
TEP 102 (sent back to WG)
TEP 103 (responding to Ramesh)
TEP 108 (ready for external review?)
TEP 109: Sensorboards (attached)
Phil
-------------- next part --------------
=========================
Sensors and Sensor Boards
=========================
:TEP: 109
:Group: Core Working Group
:Type: Documentary
:Status: Draft
:TinyOS-Version: 2.x
:Author: David Gay, Phil Levis, Wei Hong, Joe Polastre, and Gilman Tolle
:Draft-Created: 10-Jun-2006
:Draft-Discuss: TinyOS Developer List <tinyos-devel at mail.millennium.berkeley.edu>
.. Note::
This memo documents a part of TinyOS for the TinyOS Community, and
requests discussion and suggestions for improvements. Distribution
of this memo is unlimited. This memo is in full compliance with
TEP 1.
Abstract
====================================================================
This memo documents how sensor drivers are organized in TinyOS and how
sets of sensor drivers are combined into sensor boards and sensor
platforms, along with general principles followed by the components
that provide access to sensors.
1. Principles
====================================================================
This section describes the basic organization principles for sensor
drivers in TinyOS.
For background, a sensor may be attached to the microcontroller on a
TinyOS platform through a few different types of connections:
* Included within the microcontroller itself
* Connected to general-purpose IO pins for level/edge detection
* Connected to an ADC in the microcontroller for voltage sampling
* Connected to general-purpose IO pins for digital communication
* Connected through a standard digital bus protocol (1-Wire, I2C, SPI)
Physically, these connections may also be decoupled by attaching the
sensors to a `sensor board`, which can be removed from the TinyOS
platform, and may fit multiple different TinyOS platforms.
The capabilities of a physical sensor are made available to a TinyOS
application through a `sensor driver`.
According to the HAA [TEP2]_, TinyOS devices should provide both
simple hardware-independent interfaces for common-case use (HIL) and
rich hardware-dependent interfaces for special-case use (HAL). Sensor
drivers should follow this spirit as well.
TinyOS 2.x represents each sensor as an individual component. This
allows the compilation process to minimize the amount of code
included. A sensor board containing multiple sensors should be
represented as a collection of components, one for each sensor,
contained within a sensor board directory.
Sensors, being physical devices that may be shared, can benefit from
virtualization and arbitration. This document describes a design
pattern for sensor virtualization that may be followed by sensor
drivers.
The same physical sensor may be attached to multiple different TinyOS
platforms, through platform-dependent interconnections. The common
logic of sensor driver should be factored into chip-dependent,
platform-independent components, and those components should be bound
to the hardware resources on a platform by platform-dependent
components, and to the hardware resources on a sensor board by
sensorboard-dependent components.
A physical sensor has a general class and a specific set of
performance characteristics, captured by the make and model of the
sensor itself. The naming of the sensor driver components should
reflect the specifc name of the sensor, and optionally provide a
component with a generic name for application authors who only care
about the general class of the sensor.
This document assumes that sensors return uninterpreted values of
arbitrary size or datatype. Conversion of sensor values to something
with actual physical meaning is beyond the scope of this document.
2. Sensor HIL Components
====================================================================
A sensor HIL component MUST provide:
- One or more SID interfaces [TEP114]_, for reading data.
A sensor HIL component MAY provide:
- One or more SID interfaces [TEP114]_, for reading or
writing calibration coefficients or control registers.
A sensor device driver SHOULD be a generic component that virtualizes
access to the sensor. A sensor device driver can provide such
virtualization for itself by defining a nesC generic client
component. When a client component is being used, a call to a
top-level SID interface should be delayed when the device is busy,
rather than failing. This virtualization may be easier to accomplish
by using one of the arbiters provided by the system.
For example::
generic configuration SensirionSht11C() {
provides interface Read<uint16_t> as Temperature;
provides interface ReadStream<uint16_t> as TemperatureStream;
provides interface Read<uint16_t> as Humidity;
provides interface ReadStream<uint16_t> as HumidityStream;
}
implementation {
// connect to the ADC HIL, GPIO HAL, or sensor's HAL
}
When a HIL component is being used, the sensor MUST initialize itself,
either by including the `MainC` component and wiring to the
`SoftwareInit` interface, or by allowing a lower-level component (like
an ADC) to initialize itself.
In addition, the HIL sensor driver MUST start the physical sensor
automatically. For sensors without a constant power draw, the sensor
MAY be started once at boot time by wiring to the `MainC.Boot`
interface. Sensors that draw appreciable power MUST be started in
response to a call to one of the top-level SID interfaces, and stopped
some time after that call completes. One of the power-management
components described in [TEP115]_ may be useful for this purpose.
Generally, simple types are made up of octets. However, sensor values
often have levels of precision besides a multiple of 8. A device MAY
specify the precision of one of its interfaces with the DeviceMetadata
interface::
interface DeviceMetadata {
command uint8_t getSignificantBits();
}
The name of the instance of DeviceMetadata SHOULD clearly indicate
which interface it corresponds to.
A value contained returned from the device through a SID interface
MAY be left shifted so that it covers as much of the type's range as
possible. For example, if a 12-bit ADC reading is presented as a
16-bit Read interface::
component DemoSensorC {
provides interface Read<uint16_t>;
}
then the driver MAY shift the 12-bit value left so that its range is
0x0000 - 0xfff0, rather than 0x0000 - 0x0fff.
Sensor driver components SHOULD be named according to the make and
model of the sensing device being presented. Using specific names
gives the developer the option to bind to a particular sensor, which
provides compile-time detection of missing sensors. However, wrapper
components using "common" names MAY also be provided by the driver
author, to support application developers who are only concerned with
the particular type of the sensor and not its make, model, or detailed
performance characteristics.
A "common" naming layer atop a HIL may look like this::
generic configuration TemperatureC() {
provides interface Read<uint16_t>;
provides interface ReadStream<uint16_t>;
}
implementation {
components new SensirionSht11C();
Read = SensirionSht11C.Temperature;
ReadStream = SensirionSht11C.TemperatureStream;
}
generic configuration HumidityC() {
provides interface Read<uint16_t>;
provides interface ReadStream<uint16_t>;
}
implementation {
components new SensirionSht11C();
Read = SensirionSht11C.Humidity;
ReadStream = SensirionSht11C.HumidityStream;
}
3. Sensor HAL Components
====================================================================
Sensors with a richer interface than would be supported by the SID
interfaces MAY provide a HAL component in addition to a HIL
component.
A sensor HAL component MUST provide:
- A SID-based interface or a specific hardware-dependent interface
with commands for sampling and controlling the sensor device.
A sensor HAL component MAY need to provide:
- A `StdControl` or `SplitControl` interface for manual power
management by the user, following the conventions described in
[TEP115]_.
- A Resource[] interface for requesting access to the device and
possibly performing automated power management.
- Any other interfaces needed to control the device.
For example::
configuration SensirionSht11DeviceC {
provides interface Resource[ uint8_t client ];
provides interface SensirionSht11[ uint8_t client ];
}
implementation {
// connect to the sensor's platform-dependent HPL here
}
4. Sensor HPL Components
====================================================================
A sensor HPL is necessarily platform-dependent or
sensorboard-dependent. These components should provide access to the
physical resources needed by the sensor, in a platform-independent
manner that can be used by the shared logic of the sensor HAL
components. In the case of bus-based sensors, this HPL may be nothing
more than wiring to the appropriate bus interface for use by the HAL
component.
For example::
configuration HplSensirionSht11C {
provides interface Init;
provides interface Resource[ uint8_t id ];
provides interface GeneralIO as DATA;
provides interface GeneralIO as SCK;
provides interface GpioInterrupt as InterruptDATA;
}
implementation {
// connect to platform or sensorboard-dependent resources
// power-manage the sensor through platform-specific means
}
5. Directory Organization Guidelines
====================================================================
Because the same physical sensor may be attached to TinyOS platforms
in many different ways, the organization of sensor drivers should
reflect the distinction between sensor and sensor interconnect.
Sensor components commonly exist at three levels:
platform-independent, sensorboard-dependent, and
platform-dependent. Factoring a sensor driver into these three pieces
allows for greater code reuse when the same sensor is attached to
different sensorboards or platforms.
Platform-independent sensor driver components for a particular sensor,
like protocol logic, when in the core TinyOS 2.x source tree, SHOULD
be placed into "tos/chips/<sensor>", where <sensor> reflects the make
and model of the sensor device being supported. When not a part of the
core source tree, this directory can be placed anywhere as long as the
nesC compiler recieves a `-I` directive pointing to the sensor's
directory. However, not all sensors have a sufficiently large amount
of platform-independent logic to justify a separate "chips"
directory. Sensor chips are more likely to be digital sensors than
analog sensors, for example.
A sensor board is a collection of sensor components with a fixed name,
intended for attachment to multiple platforms. Each sensor board MUST
have its own directory named <sensorboard>. Default TinyOS 2.x sensor
boards are placed in "tos/sensorboards/<sensorboard>", but sensor
board directories can be placed anywhere as long as the nesC compiler
receives a `-I` directive pointing to the sensor board's directory.
Both sensors and sensor boards MUST have unique names. Case is
significant, but two sensor boards MUST differ in more than case. This
is necessary to support platforms where filename case differences are
not significant.
Each sensor board directory MUST contain a `.sensor` file. This file
is a perl script which gets executed as part of the `ncc` nesC
compiler frontend. It can add or modify any compile-time options
necessary for a particular sensor board. It MAY modify the following
perl variables, and MUST NOT modify any others:
- @new_args: This is the array of arguments which will be passed to
nescc. For instance, you might add an include directive to @new_args
with push @new_args, `-Isomedir`. This could be used to include
subdirectories.
- @commonboards: This can be set to a list of sensor board names which
should be added to the include path list. These sensor boards must be
in tinyos-2.x/tos/sensorboards.
If the sensor board wishes to define any C types or constants, it
SHOULD place these in a file named <sensorboard>.h in the sensor
board's directory.
A sensor board directory MAY contain a "chips" directory, with
subdirectories for each of the sensors connected to the sensor board.
If a "chips" subdirectory is used, sensorboard-dependent driver
components needed to connect platform-independent logic to a
particular attachment for that sensor should be placed in
"<sensorboard>/chips/<sensor>".
Components needed to connect the platform-independent sensor driver
components or sensorboard-dependent components to the hardware
resources available on a particular platform SHOULD be placed in
"tos/<platform>/chips/<sensor>". In addition, components for a sensor
that only exists on a particular platform should be placed in a such a
directory.
Sensors that exist as part of a larger chip, like a MCU internal
voltage sensor, SHOULD be placed in a subdirectory of the chip's
directory. "tos/<chip>/sensors/<sensor>".
The `.platform` and `.sensor` files need to include enough `-I`
directives to locate all of the necessary components needed to support
the sensors on a platform and/or sensorboard.
All of these directory organization guidelines are only intended for
code that will enter the core source tree. In general, sensor
components may be placed anywhere as long as the nesC compiler
receives enough `-I` directives to locate all of the necessary pieces.
6. Authors' Addresses
====================================================================
| David Gay
| 2150 Shattuck Ave, Suite 1300
| Intel Research
| Berkeley, CA 94704
|
| phone - +1 510 495 3055
|
| email - david.e.gay at intel.com
|
| Wei Hong
| Arch Rock
| 657 Mission St. Suite 600
| San Francisco, CA 94105
|
| email - wei.hong at gmail.com
|
| Philip Levis
| 358 Gates Hall
| Computer Science Department
| 353 Serra Mall
| Stanford, CA 94305
|
| phone - +1 650 725 9046
|
| email - pal at cs.stanford.edu
|
| Joe Polastre
| 467 Soda Hall
| UC Berkeley
| Berkeley, CA 94720
|
| email - polastre at cs.berkeley.edu
|
| Gilman Tolle
| Arch Rock
| 657 Mission St. Suite 600
| San Francisco, CA 94105
|
| email - gtolle at archrock.com
7. Citations
====================================================================
.. [TEP2] TEP 2: Hardware Abstraction Architecture
.. [TEP114] TEP 114: SIDs: Source and Sink Indepedent Drivers
.. [TEP115] TEP 115: Power Management of Non-Virtualized Devices
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.millennium.berkeley.edu/pipermail/tinyos-2.0wg/attachments/20060905/ae173f28/tep109-0001.html
-------------- next part --------------
More information about the Tinyos-2.0wg
mailing list