Ehsan Nourbakhsh’s Blog » General

Symbol Table Manipulation in TinyOS

Ehsan — Tue, 10 Jan 2012 01:13:25 +0000

I realized one of the hacks we had used in our testbed is of use to other researchers as well. When running an experiment using MEMSIC Motes, it is possible that you need a large number of images which only differ in some variable values. For example, only the variable indicating start time for each of them is different.

Instead of changing the variable and recompiling, you can do the following. Declare your desired variable(s) as

extern const uint8_t myVar;

After compiling the main image, take a look at your symbol table by typing

 tos-set-symbols --read /path/to/main.exe

This will show a table like following:

AMQueueImplP__0__current             :  01  [.]  (1)
AMQueueImplP__1__current             :  01  [.]  (1)
ActiveMessageAddressC__addr          :  01 00  [..]  (1)
ArbiterP__0__resId                   :  01  [.]  (1)
CC1000RssiP__currentOp               :  04  [.]  (4)
CC1000SendReceiveP__BIT_CORRECTION   :  1b 1c 1e 20 22 24 26 28  [... "$&(]
CC1000SendReceiveP__rxBufPtr         :  5c 02  [\.]  (604)
CC1000SquelchP__clearThreshold       :  20 01  [ .]  (288)
MyModule__myVar              :  00 00  [..]  (500)
SerialDispatcherP__0__messagePtrs    :  fb 02 2a 03  [..*.]  (53084923)
SerialDispatcherP__0__receiveBuffer  :  fb 02  [..]  (763)
SerialDispatcherP__0__recvType       :  ff  [.]  (255)
TOS_NODE_ID                          :  01 00  [..]  (1)
atm128_stdout                        :  00 00 00 02 00 00 00 00 fb
00 00 00 00  [..............]

Now you can set the value of corresponding variable in the symbol table using the following command:

tos-set-symbol /path/to/main.exe MyModule__myVar=1234

This allows you to directly set the value of your desired variable. Just be careful, as any programmer should be, about variable types.
tos-set-symbols is part of the avr-gcc environment, and uses avr-objdump.

Initially we used this method to generate new images with different node IDs (TOS_NODE_ID variable) from the same base image. Now our testbed’s web based interface allows the user to draw a topology visually and assign such variable values to each of the nodes. It can also automatically map your desired topology to available nodes in the testbed.

Finals week in Austin

Ehsan — Sun, 11 Dec 2011 19:31:00 +0000

Nice view Thank goodness I don’t have exams anymore.

Google: Engineers vs. Brand Loyalty

Ehsan — Mon, 05 Dec 2011 04:47:29 +0000

Almost a month ago Google changed its Google Reader product by removing one of its core features: social sharing. This feature allowed you to share items you had read in Reader with your ‘friends’ in Reader community. You could also follow them, comment on their items and so on. Since your comments and notes were only text, the communities were formed around type of ideas they embraced rather than looks. Furthermore, your semi-anonymous Reader identity made the concentration on context more emphasized. In my personal opinion, the resulting network enjoyed a much more intellectual atmosphere than other more sophisticated social networks do.

In order to promote their main socail network, Google Plus, they eliminiated Reader’s features with no provision of seemless migration. I can see this as an engineer’s assumption that new “toys” automatically attract new people. Marketing people might disagree, pointing to brand loyalty.

The engineering versus marketing approach Google took towards Reader reminds me of their Android operating system. In October Michael DeGusta of The Understatement summarized his observations about Android updates for devices shipped between 2008 and 2010 as a chart. His visualization shows a clear message: Google does not intend to support their older devices.

My own experience supports this horrifying observation. While I am not sure about internals of Android’s framework and drivers, the ending result for users like me has been shaky reliance on courtesy of application developers to include my device in their small list of supported devices.

My experience with iPhone and Windows Mobile/Phone have been clearly different. The fact that I still receive updates for my 4 years old device says a lot. But the problem with iOS is it only has one active line of devices. You can get a newer version of iPhone but that is your only choice. However, Windows Phone has been more welcoming. My observation was WP7 suffered a poor release process, including poor support of developers in the early days and taking months before releasing copy & paste capability in an update. I hope they don’t make the same mistake again, and I can safely return to Windows Mobile family!

Update: I ran into another article discussing how internal instant messaging products of Google are not “synchronized” with each other. In my opinion it shows lack of a unified standard layer between users and Google products. As a friend pointed out, Google has been more concerned about shipping new products faster rather than keeping them synchronized.

IMAP and Microsoft Office Outlook 2007

Ehsan — Thu, 30 Dec 2010 07:51:24 +0000

This summer I had to use Outlook 2007 with Microsoft Exchange server. It was also integrated with Cisco’s WebEx. This combination was so efficient that I started to wonder why I did not use Outlook in school.

But after a one semester trial, I am completely disappointed. Apparently Outlook is not intended for use with an IMAP server. Each time it would take almost minutes to load messages. For Thunderbird, it was merely seconds on the same server.

Apparently Microsoft developers are aware of this problem, but it is not fixed yet. There are hacks and suggestion to improve it, such as this one. Unfortunately these “solutions” don’t fit my needs and I am back to using good old Mozilla Thunderbird.

Just Testing

Ehsan — Tue, 18 May 2010 00:08:35 +0000

Home eNB: Great Oppotunity for 3GPP LTE

Ehsan — Sat, 11 Apr 2009 02:38:01 +0000

In the recent years more and more wireless providers have started to provide femtocells to their customers. The customer can deploy the femtocell in any location that the coverage of normal towers are weak or absent. Consider a product like Samsung’s Ubicell. The user can plug this femtocell in their home internet switch, and use their regular cell phone to connect to the final service provider, e.g. Sprint.

E-UTRAN architecture from 3GPP document 36.300-880

As of December 2008, 3GPP documentation for Long Term Evolution networks has started to mention Home eNB as part of the Evolved UTRAN. This move can be a significant advantage for the final users, only if service providers fully recognize the extent of service this final addition can offer. This recognition might require a careful study of 802.11a/b/g Access Points, considering the similarities of the two products. Both these products are the front end of a network to final customers. While these final points are accessible to the customers, the actual network is not controlled by them.

Most APs initially were merely wireless transmitters, but they soon started evolving into more sophisticated equipments. The need to provide more functionality for the end user to adjust settings, e.g. channel or user access rules, resulted in simple interfaces to configure the AP. Currently wireless APs are commonly acting as firewalls, switches, DSL modems. But the true revolution for the APs happened when vendors such as Linksys started to provide open source firmware for their products. Because of the delay in this revolution, many golden opportunities are gone and we do not see as many diverse applications.

Given how larger organization such as universities might consider deploying a number of Home eNBs throughout their campus, there is a high level of interaction that would be only limited to these eNBs. As an example, in a university campus many calls and data interactions would be between students on the same area. Or consider an event like SXSW. While this year AT&T added enough resources to guarantee good coverage, smaller scale events do not motivate service provider to make such adjustments. Instead the organizing institute is well aware of the scale and the available resources and would be able to allocate more eNBs to the event area. One other aspect is access control: if I am paying for a Home eNB, I may not want my neighbor to user it for free unless it is an emergency call.

By providing good configuration options to the deploying organization, all sides of such scenario would benefit: the organization would enjoy faster service on their campus, the service provider would not have to worry about resource management and the manufacturer would ensure better sale of its products.

There are many challenges in providing such control to the final user. However, I believe the designers of 3GPP LTE have started taking initial steps and now the manufacturers need to move forward.

Atomicity

Ehsan — Thu, 01 May 2008 01:03:13 +0000

During my undergrad Database course, our professor explained atomicity of transactions with the very trivial example of withdrawing cash from ATM machines: either your whole transaction should fail or it should completely succeed. It means your account balance should not change unless you have got your money, and if you have received the cash your account balance should have also decreased.

Unfortunately some of the people who actually design ATM machines have not passed this course it seems. Last Wednesday I withdrew some cash from an ordinary ATM, and the machine failed to return my cash. But my account balance was reduced! The machine actually was able to tell me that it had failed and the operation was canceled, but it seems it forgot to tell its friends back in the Wells Fargo network to cancel the operation. I had to call the customer service a couple of times to get my money back.

There is no conclusion from this post. It just surprised me that a simple basic idea we are taught in classes is not actually implemented in real life.

UPDATE: My old friend Pooya asked in the comments if the ATM in question was a Diebold ATM. Diebold is the company that also makes voting machines in US. Next time I was in Student Union I checked the ATM, and guess what: it is a Diebold ATM! I now have some serious questions in my mind!

I should mention that Wells Fargo checking people were very nice and quick and solved my issue by a couple of phone calls.

Capability Maturity Model Integration (CMMI)

Ehsan — Wed, 26 Sep 2007 16:10:28 +0000

There are concepts that seem to be obvious when you read them in a book. But when you try to practically perform them in the real world, you see the many details that you did not notice before. Software engineering is one area in which this happens a lot. Most of the topics look very basic and you think by yourself that these are what we do naturally. But if an institute is not really careful, they will soon find out that routines have gone out of control. Divisions start to short-cut the procedures to get faster results. So the necessary details needed for the intended perfection of final product or service are not achieved. And if an assessment is performed, everyone is sure they ‘almost’ did all the procedures precisely.

CMMI, from my point of view, is the key to solving this problem. If this model is used it focuses on identifying processes, refining them and then keeps tuning them and revising them over time. This way you can expect to reach your standards after a time, instead of wildly applying different software engineering methods.

During my Software Project Management course with Dr. Mili, me and my two other teammates Jason and Shiva did a presentation on the CMMI topic. This was one of the many topics covered in the course, some of them by students in the form of presentations. I had already taken this course during my undergrad, but my short work experience showed me how important it is to know these things. From my point of view, this course is one of the things that distinguishes a manager from a developer. Also knowing topics covered in this course enables you to talk to higher management fluently.

Anyways, we used a Subversion repository for revision control. It was not very efficient in terms of conflict resolution because of the fact that we could not use diff on powerpoint files. But using subversion was definitely advantageous since we could update each other without sending messy emails with huge attachments.

The final presentation is available here, printable version here. I highly recommend the course in case you are considering computer related jobs in future.

diggy night

Ehsan — Wed, 02 May 2007 03:52:18 +0000

I can’t resist writing it. Takes 5 minutes of my qualifier exam time, but is worth it.

A digg user posted an item about a HD-DVD code, and the fact it was taken down because of a takedown notice. Digg removed that. People noticed that and informed each other of Digg’s removing the dugg story. But Digg removed those too. People dugg all of this again, Digg un-dugged. People dugg, ….

The result? Look at this:

You think it is over? NO! The same is happening with Wikipedia: http://en.wikipedia.org/wiki/HDDVD_Night. People [write in] wiki, Wiki removes. People (write in) wiki, ….

Tragedy at Virginia Tech

Ehsan — Wed, 18 Apr 2007 03:41:57 +0000

This is so sad to witness people lose their lives. There is no need to say how depressing, shocking and terrible it is to know they were some young students, attending their daily classes. This is so sad, so unacceptable.

Even in something like this some people show courage:

Liviu Librescu, 76, an engineering science and mathematics lecturer, tried to stop the gunman from entering his classroom by blocking the door before he was fatally shot, his son said Tuesday from Tel Aviv. [Yahoo! news]

I truly sympathize with families of the victims.