Building DASH7 Apps with OpenTag

OpenTag: Ofﬁce Hours

JP Norair
12 May 2011

jpnorair@indigresso.com
skype: jpnorair

Copyright © DASH7 Alliance

‣ Some information about DASH7 (for noobs)
‣ What you get [with OpenTag]
OpenTag: Ofﬁce Hours
‣ Where to get it
JP Norair ‣ What you can do to help
12 May 2011

‣ Project Roadmaps
skype: jpnorair ‣ Answering your Questions


DASH7 Mode 2 is a 2nd Generation WSN/IoT/RFID Technology

433 MHz band
8 channels
Optimized for
Optimized for
Low Latency
Micro Power
(Bursty Data)

Mode 2
Universal Adaptive Data Rate
Interoperability 28 - 200 kbps

Very Fast Compact Stack
Multicast typ. 16KB


About DASH7 Alliance
Next Meeting: 21 June
• Speciﬁcation Development in San Francisco
‣ Mode 2 (basically done)
‣ “DNA” Middleware layer
‣ NFC integration
‣ More

• Market Development

• ISO Stewardship

• Go to dash7.org to see new membership
terms, and other information.


What You Get [with OpenTag]
OpenTag is a very purpose-built OS that uses DASH7 I/O

OpenTag Component What it Does

Low Level Radio Driver PHY & MAC Control

System Event and Session Manager (OS-like)

Network Protocols (M2NP, M2DP, M2AdvP) Routing, Raw Data, Group Synchronization

Transport Protocols (M2QP) Query / Data Acquisition, Data Transfer

Filesystem Read, Write, Create, Delete, Etc.

Application Modules Built-in Apps (none yet)

C API Library functions (Programming apps in C on the same device)

Serial API(s) Client-Server (Communicating the apps via another device)


Where to Get it

Signup, Forums, Mailing List, other support

http://sourceforge.net/projects/opentag

Latest Code Download (use Git)

git clone git://opentag.sourceforge.net/gitroot/opentag/OpenTag_M2

OpenTag and Mode 2 Wiki (in continuous development)

http://www.indigresso.com/wiki


Where to Get it

Signup, Forums, Mailing List, other support

http://sourceforge.net/projects/opentag

Latest Code Download (use Git)
Don’t understand Git?
git clone git://opentag.sourceforge.net/gitroot/opentag/OpenTag_M2
Google is your friend
(Git documentation is good)
OpenTag and Mode 2 Wiki (in continuous development)

http://www.indigresso.com/wiki


How You Can Help

Core
Beta Testing Development Documenting


How You Can Help

Core

• Currently about 3 Beta testers
(you know who you are: if you
want to be recognized, email me)

• Download the code, compile,
and play with it. You will ﬁnd
bugs and have questions.
‣ Send messages on developers
mailing list (sourceforge).
‣ Skype me, for quick info


How You Can Help

Core

• Currently about 3 Beta testers • Currently just me (officially)
want to be recognized, email me) • Requires a good understanding
of the code and specification
• Download the code, compile, ‣ My estimation: will take you
and play with it. You will find 3-6 weeks to get here
‣ Send messages on developers • Two possibilities
‣ OT library development
‣ Skype me, for quick info ‣ Porting to other platforms


How You Can Help

Core

• Currently about 3 Beta testers • Currently just me (officially) • Currently just me
want to be recognized, email me) • Requires a good understanding • Requires a good understanding
of the code and specification of the code or specification
• Download the code, compile, ‣ My estimation: will take you
and play with it. You will find 3-6 weeks to get here • Many possibilities
‣ Wiki
‣ Send messages on developers • Two possibilities ‣ Formal documents
‣ OT library development ‣ Academic research papers
‣ Skype me, for quick info ‣ Porting to other platforms


Feature Roadmap: Now it is a Race



SS Pre-alpha & Alpha:
Module testing and simulation
(usually on PC)



(usually on PC)

SS Beta 0 (current):
Initial Platform Testing (CC430)
without Serial API, not all
features are complete



(usually on PC) SS Beta 1:
Testing platform(s) using Serial
API, and completion of all
features for version 1.0




Testing platform(s) using Serial
API, and completion of all
features for version 1.0

SS Beta 2:
Feature complete debug and
ofﬁcial compliance testing




Testing platform(s) using Serial SS Version 1.0:
API, and completion of all Bundling of ofﬁcial code
features for version 1.0 packages for platforms

SS Beta 2:




Testing platform(s) using Serial SS Version 1.0:
API, and completion of all Bundling of ofﬁcial code
features for version 1.0 packages for platforms

SS Beta 2:
position


Planned Platform Support (Ofﬁcial)

Beta 0:
CC430, POSIX Simulator

Beta 1:
Beta 0 + ADuCRF101 +
SX1231 Module

Beta 2:
No additional, planned
“ofﬁcial” platforms


Planned Platform Support (Official)

Beta 0:
CC430, POSIX Simulator

Beta 1:
Beta 0 + ADuCRF101 +
SX1231 Module

“Official” just means that I personally
know it works. If you develop a Beta 2:
working platform and send one to No additional, planned
me, I will make it official
“official” platforms


Case Studies (Comprehensive Answers to Recently Asked Questions)

‣ How does OpenTag enable location derivation?
‣ Can OpenTag do multihop and mesh?
‣ How are events processed?
‣ How many simultaneous connections are supported?
‣ How is data stored and logged?
‣ What is the deal with wireless regulations at 433 MHz?


How does OpenTag
enable location derivation?


DASH7 Mode 2 Has Two Features that Enable Location Derivation
Feature 1: Normalized RSSI

Without Normalized RSSI
With Normalized RSSI
Devices need to know
Devices in a network are free to
conﬁgurations of all other
use different power outputs
devices in the network

Open Loop Closed Loop



DASH7 Mode 2 Foreground Frame Architecture
Length TX EIRP Subnet Frame Other Data Footers CRC
(Bytes) (0.5 dBm) Filter Control Headers Payload (crypto)

1 Byte 1 Byte 1 Byte 1 Byte 0-52 Bytes 0-249 Bytes 0-40 Bytes 2 Bytes

0-255 -40 to 23.5 — — (optional) — (optional) —

Mode 2 transmissions tell the
receiver how much power was used,
so the receiver can normalize the
RSSI dynamically



DASH7 Mode 2 Foreground Frame Architecture
Length TX EIRP Subnet Frame Other Data Footers CRC
(Bytes) (0.5 dBm) Filter Control Headers Payload (crypto)

1 Byte 1 Byte 1 Byte 1 Byte 0-52 Bytes 0-249 Bytes 0-40 Bytes 2 Bytes

0-255 -40 to 23.5 — — (optional) — (optional) —

Mode 2 transmissions tell the This feature can be used to enable
receiver how much power was used, location derivation and also to ﬁlter
so the receiver can normalize the out transmissions that are too far
RSSI dynamically away (conﬁgurable)


(2) Buferring Location Data

Location can be derived from
Location List an algorithm that uses data
Flags Device ID Loc. Data from multiple coordinates
coord 1
1 Byte 2/8 Bytes 3 Bytes

Flags Device ID Loc. Data
Location Coordinate coord 2

1 Byte 2/8 Bytes 3 Bytes Flags Device ID Loc. Data
coord 3

…
Data may contain normalized RSSI’s Flags Device ID Loc. Data
from 1 to 3 antennas, and also angle coord N
of incidence information


(2) Buferring Location Data

Location can be derived from
Location List an algorithm that uses data
Flags Device ID Loc. Data from multiple coordinates
coord 1

Location Coordinate coord 2 DASH7 does not specify the
algorithm to use, just the way
data is stored. The algorithm
1 Byte 2/8 Bytes 3 Bytes Flags Device ID Loc. Data
coord 3 is up to you!

…
Data may contain normalized RSSI’s Flags Device ID Loc. Data
from 1 to 3 antennas, and also angle coord N
of incidence information


OpenTag Implements Normalized RSSI

DASH7 Location Usage
Features RSSI is implemented in the Radio
Driver. During any reception,
Normalized RSSI
OpenTag buffers the non-
Angle of Incidence
normalized RSSI value on each
antenna (typically 1) You can get it
by calling radio_rssi()

Requires special HW, not
currently tested or
implemented in OpenTag



Normalized RSSI
Angle of Incidence

OpenTag can be conﬁgured to
automatically normalize and
populate the location list.
currently tested or



Normalized RSSI
Angle of Incidence

OpenTag can be conﬁgured to
automatically normalize and
populate the location list.
currently tested or
Your algorithm needs to read
this data and do the rest


One Example of Using RSSI for Location
Using large numbers of low-cost, battery-powered ﬁxed position nodes is cheap and precise

Fixed Position Node

Node with Location Algorithm
(knows positions of ﬁxed nodes)
(packet data)

Mobile Node


One Example of Using RSSI for Location
Using large numbers of low-cost, battery-powered ﬁxed position nodes is cheap and precise

(packet data)

(location list)

(derived location
of mobile node)


Can OpenTag [and DASH7]
do Multihop and Mesh?


DASH7 Mode 2 & OpenTag Support Limited Multihopping
DASH7‘s advanced query functionality and long range deprecate needs for complex hopping

One Hop Two Hops 3 to 15 Hops

– Anycast Request – Anycast Request
Routing Support All
– Unicast Response – Unicast Response

Built-in, available to Requires 3rd Party
Integration Automated
application layer routing table algorithm


DASH7 Mode 2 & OpenTag Support Limited Multihopping
DASH7‘s advanced query functionality and long range deprecate needs for complex hopping

One Hop Two Hops 3 to 15 Hops

– Anycast Request – Anycast Request
Routing Support All
– Unicast Response – Unicast Response

Built-in, available to Requires 3rd Party
Integration Automated
application layer routing table algorithm

Enables simple repeaters If you want to build a mesh
network, you would need to
integrate a routing algorithm.
RPL is one example.


DASH7 Mode 2 Network Routing Template

Routable DASH7 Mode 2 frame, as seen by network protocol
Data Link Layer Mode 2 Network Protocol M2DLL
(M2DLL) (M2NP)
Length Data Link M2NLS Routing M2NP M2NLS DLLS
(Bytes) Headers Header Header Payload Auth. Data Auth. Data

1 Byte 7-38 Bytes 1-25 Bytes 1-18 Bytes 0-245 Bytes 0-20 Bytes 0-20 Bytes

(optional) (optional) (optional) (optional)

For Data Link Layer
Security

For Network Layer
Security


DASH7 Mode 2 Network Routing Template

Routable DASH7 Mode 2 frame, as seen by network protocol
Data Link Layer Mode 2 Network Protocol M2DLL
(M2DLL) (M2NP)
Length Data Link M2NLS Routing M2NP M2NLS DLLS
(Bytes) Headers Header Header Payload Auth. Data Auth. Data

1 Byte 7-38 Bytes 1-25 Bytes 1-18 Bytes 0-245 Bytes 0-20 Bytes 0-20 Bytes

(optional) (optional) (optional) (optional)

For Data Link Layer
Hop Hop Origin Destination
Control Extension Device ID Device ID
Security
1 Byte 1 Byte 2/8 Bytes 2/8 Bytes
For Network Layer
(optional) (optional) (optional)
Security
The Built-in two hop leverages the Origin and
Destination IDs, which are additional to the
Data Link Layer addressing (Source and Target)


Routing Functions in OpenTag Network Module

• Function network_route_ff() is
automatically called by OpenTag when
parsing an incoming frame
‣ returns 0 if the frame is routed to this device
So, to implement sophisticated multihop or
‣ returns positive number (corresponding to mesh routing, you need to integrate your
routing table index) if frame is routed to a routing table and routing algorithm into this
known device function, network_route_ff()
‣ returns -1 if frame should be discarded

• Function m2np_header() writes a properly
routed M2NP header to a new frame.
‣ routing algorithm needs to store the routing
information in the m2np data structure, so
m2np_header() can use it.
‣ m2np data structure is exposed, so you can
put routing algorithm anywhere you want.


Routing Functions in OpenTag Network Module

• Function network_route_ff() is
automatically called by OpenTag when
parsing an incoming frame
‣ returns 0 if the frame is routed to this device
So, to implement sophisticated multihop or
‣ returns positive number (corresponding to mesh routing, you need to integrate your
routing table index) if frame is routed to a routing table and routing algorithm into this
known device function, network_route_ff()
‣ returns -1 if frame should be discarded

• Function m2np_header() writes a properly
routed M2NP header to a new frame. Remember, normalized RSSI
information is already part of
‣ routing algorithm needs to store the routing
DASH7, so routing algorithms
information in the m2np data structure, so
that use link budget data are
m2np_header() can use it.
well suited.
‣ m2np data structure is exposed, so you can
put routing algorithm anywhere you want.


How are events processed?
(and, how good is the event
timing resolution)


What is an Event?
(For those among us who are not software nerds)

An event is anything that causes a program to stop doing what it is doing,
and start doing something else.

Some Examples

Pushing a Button An API Call

Getting a Sensor
A Timer expiring
Reading


Events in OpenTag

• OpenTag includes an event and task manager that runs parallel to the user’s application

• When an event occurs, OpenTag takes control of the system in order to run the task associated with the
event. It gives back control when the Task is done (or when it’s idle)

Event
Associated Tasks Notes
(Descending Priority)

Internal RF interrupt Low Level Radio Control Transparent to Application

API Call Generate new request Application dependent

Sensor Detect Generate new request Application dependent

Automated tasks:
- Listen for data [Mostly] Transparent to
System Timer Expires
- Prepare response Application
- Send Beacon


Events in OpenTag

• OpenTag includes an event and task manager that runs parallel to the user’s application

• When an event occurs, OpenTag takes control of the system in order to run the task associated with the
event. It gives back control when the Task is done (or when it’s idle)

Event
Associated Tasks Notes
(Descending Priority)
For SoC’s/SiP’s,
Internal RF interrupt Low Level Radio Control Transparent to Application totally transparent

API Call Generate new request Application dependent

Sensor Detect Generate new request Application dependent

Automated tasks:
- Listen for data [Mostly] Transparent to Needs a dedicated
System Timer Expires timer resource.
- Prepare response Application
- Send Beacon


What Actually Happens when an Event Occurs?

No Task
Automated Tasks
Pending (Descending Priority)
Event
Event Mgr checks Radio RX/TX
Occurs what task is
pending
Activate Session
Run Task
Initialize Channel Scan

Send Beacon

• Any event must call sys_event_manager() in the system module
(system.c) in order to bind a task to the event that just occurred.
‣ System Timer Events are managed internally by OpenTag, so when the
system timer expires, the appropriate task is automatically processed.
‣ The system timer is always running. So events can be queued up
during OpenTag tasks (expired events are discarded).


How Fast is the Event Timing Resolution?

• The OpenTag system timer runs at a resolution The application layer, thus,
of “1 tick,” where 1 tick = 1/1024 sec needs to have worst case
‣ Roughly 1 ms latency of 1 tick.
‣ Allows usage of 32768 Hz crystal as source

• There is another timer unit called a “short tick”
equal to 1/32768 sec (~30.5 µs)
‣ Not used at all in OpenTag library (OTlib)
‣ Used only for internal radio processes,
although certain radios have internal timers
and don’t need to use an MCU timer at all.
‣ All DASH7 processes are timed in ticks. So Since this is internal, you could use
short ticks are only necessary if you are an another clock source and achieve a
optimizer and want to establish internal timer higher resolution, but you would need to
offsets that are shorter than 1 tick. write some new driver code.


How many simultaneous
connections are supported?


This Answer Depends on What You Mean by “Connection”
Connection Model 1 • Answer: 1
(Isochronous, streaming data) ‣ This is like cable-replacement, which is not
something DASH7 is designed to do well.
‣ Requires either complex time-slotting (like GSM,
Master Bluetooth) or even more complex MIMO
(802.11n, CDMA, OFDM) in order to support
multiple isochronous connections via wireless.

Slave Slave Slave


Connection Model 1 • Answer: 1
(Isochronous, streaming data) ‣ This is like cable-replacement, which is not
something DASH7 is designed to do well.
‣ Requires either complex time-slotting (like GSM,
Master Bluetooth) or even more complex MIMO
(802.11n, CDMA, OFDM) in order to support
multiple isochronous connections via wireless.

Slave Slave Slave

In Hardware language, this is
usually referred to as a “bus”


Connection Model 2 • Answer: a lot (potentially 1000’s)
(Bursty, queued data) ‣ This is broadcast-query-respond, which DASH7
is designed to do especially well.
‣ Basic queries of thousands of devices can be
Node accomplished without much overhead.
Collector
‣ Follow-up dialogs with queried devices is limited
Node by available memory and idle-time conﬁguration
Node
Node Node


How is data stored
and logged?


Answer: The Built in Filesystem

GFB ISFB
(General File Block) (Indexed Short File Block)

Functions Read, Write, Create, Delete

Security POSIX-like, with optional crypto

Max File Size 65 KB 255 Bytes

Max Files 256 256

Files used by DASH7 0 33 reserved

Searchable No Yes

Executable Yes Yes
Byte-centric, Big-Endian + some ﬁles
File Structure Binary (App. Dependent) have standardized structure


Using the OpenTag Filesystem (called Veelite)

• In C, it is a lot like using the POSIX C library
‣ FILE* — vlFILE*
‣ fopen() — vl_open(), vl_new()
‣ fclose() — vl_close()
‣ fgetc(), fputc() — vl_read(), vl_write()

• You can also access files by DASH7 itself,
using an Application Subprotocol (included in
OpenTag), as long as you have appropriate
user access to the files you want.

• The Application Subprotocol for file access is
also used over a wire, for the Serial-API, if you Client
are connecting an OpenTag module to another HW
piece of HW.


What is the deal with wireless
regulations at 433 MHz?


433 MHz is Usually Available License-free (or cheaply)
Plus: no regulations in Antarctica!

FCC 15.231 & 240
North America uses the FCC
part 15 license-free spec
Korea & Japan
have their own regulations for
license-free 433 MHz use

Limited ERC 70-03
Some countries use basically the
ERC 70-03 spec, but with certain
limitations (e.g. small fees)
required to use the spectrum.
ERC 70-03 (or similar)
Most countries in the world
use the EU/ISM 433 MHz
spec, or something similar.

433 MHz Regulatory Policy Summary

Regulation Complexity Usage Notes Simpliﬁed Speciﬁcation

Spectrum: 420 - 450 MHz (20 MHz)
Max EIRP: highly variable, but effectively -2.4 dBm
FCC Part 15.231 High General Use Max Duty Cycle: highly variable, but effectively 50%
Max TX time: highly variable, but effectively 100 ms
Beacons: requires very low duty cycle, or alternatively ! -14.4 dBm

Similar to 15.231 but with simpler rules, no allowance for beacons,
FCC Part 15.240 Moderate For Containers only and longer TX time permitted. In most cases it does not really
improve performance of DASH7 Mode 2 over 15.231.

Spectrum: 433.05 - 434.79 MHz (1.74 MHz)
ETSI ERC 70-03 Low General Use Class 1: 0 dBm @ 100% duty cycle, max TX 36 sec.
Class 2: 10 dBm @ 10% duty cycle, max TX 36 sec, listen before talk

Spectrum: 433.67 - 434.17 MHz (500 KHz)
Korean ETRI Low General Use
Max EIRP: 0 dBm
Max Duty Cycle: 100%
Max TX time: 100 ms
Japanese RR Low Logistics only
(Note: for guidance only, I am not an expert on ETRI & RR)


See you next time…

No way! I only
How about date guys who use
that one? OpenTag


See you next time…
Send more questions to:
Subject: “OpenTag Question”

No way! I only
How about date guys who use
that one? OpenTag


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