Replacement Dell Charger Not Recognized! (Autopsy of the TF2929 1-Wire Protocol EEPROM)

3 days ago, an error message popped-up on my laptop after the BIOS screen and it says Unrecognized Power Adapter like the one I found on this link. I checked the system properties and I saw that my Intel-i7 is running at 760MHz!!! No wonder my Embedded Linux compile time is very slow! With this, I opened the AC adapter and I saw this chip TF2929. Upon checking the datasheet, it is a 1-wire EEPROM. I took this out and created a 1-wire protocol software on Arduino Mega.

I created a very simple 1-wire software to detect the presence of the EEPROM. And looking at my oscilloscope.

The TF2929 doesn't respond. Explanation: On the datasheet of the EEPROM, it says there that after a Reset Low Time (in this case, it is 488microseconds), the EEPROM should respond 15 to 60microseconds after the rising edge of the Reset Low Time. As seen here, there is no reply from the TF2929 and I am confident that it is dead. Frustratingly, I can't do much at this point. Even if I buy a new TF2929, I don't have the binary file to be written to the EEPROM.

I even checked the laptop and I can see that it is sending pulses but the TF2929 doesn't respond as well. (Sorry, no screenshots) Therefore, the laptop's 1-wire master is working fine and I don't need to do anything on the mainboard.


The question now is why it  happened. This is how it was implemented.

Open-drain circuits can fail and one of their symptoms is that they couldn't sink any current and I had seen this happen. It is possible that the TF2929 can receive messages but it can't respond back because their open-drain output has been damage. If I'm the engineer in charge for this circuit, I will make it like this:

Wherein R is around 50ohms and/or not lower than 22 ohms.

Now, the only feasible thing to do at this point is to buy a replacement 90W AC adapter.



Update:  Sept 25, 2016

I bought a second hand Dell 90W AC Adapter for 7 US dollar. All my findings above are correct. Now my laptop can recognize the 90W Adapter and is now running again on full speed.

[Repair] Dell Vostro Replacement AC Adapter improvements

This is a short video demonstrating how to resolve a laptop power supply for the following problems:
- mild electric shock
- interference on audio recording (mic or guitar)

Prerequisites are:
- soldering iron
- wire
- properly grounded outlet

Cross-Compiling and Debugging C++ program on BeagleBone Black Embedded Linux using Windows (+ debugging using gdbserver / gdb)

Here is a short video  of me doing a demonstration on how to Compiler and Debug C++ Program on a BeagleBone Black using Windows machine.

Sorry for the low quality audio. I will invest on a good mic in the future.

Passing tips (HOW TO): Passed the Prince2 (Project Management) Foundation and Practitioner Exam through Self-Study

This year I was able to obtain both the Foundation and Practitioner certification in Prince2 Project Management. On this post, I will give some tips on how to pass both exams.

I enrolled at ILX Group for the online training course for both the Foundation and Practitioner exam. They also sent me an official copy of the Prince2 manual. I will assume on this post that you will be enrolling at any training centers that provides online training courses/material.

Preparing for the Foundation exam:

• This is the first exam that you must pass before going to Practitioner.
• You will be needing the Prince2 manual for the Foundation review but I don't recommend reading it yet. I will discuss that later.
• First thing you need to do is to watch ALL the videos from the training provider. They will give you good insights on what Prince2 is all about.
• After you finish all the videos, do some tries on the exam simulator based from the knowledge you gained from the video tutorials. This will give you some insights on what are needed on the exam.
• From the exam, you will notice that you need to be familiar with some objective and purpose statements which comes from the official manual. Also, be aware on the structure of the questions. Watch out for negative questions (e.g. which of this IS NOT part of Starting Up a Project)
• Now, read the Prince2 manual. Concentrate on the Themes, Processes and Principles. Read the Appendix A as well.
• Then do at least 10 practices on exam simulator.

This is a lengthy way of passing it. I read that some training centers will give you 3 days training and promise that you will be able to pass the exam. Well, I can go that way as well but I want to learn almost everything and be familiar very well with the manual. I was able to get a high mark on the Foundation exam.

On taking the Foundation exam, you will be given an hour and if you are prepared for this exam, you will be able to pass it. As there are no negative markings, don't leave any blanks. Next, Practitioner exam.

Preparing for the Practitioner exam:

• From my opinion, Foundation exam is easy. But the Practitioner is a tough exam. Tougher than the Foundation exam by 10 to 20 times. So you might want to give yourself ample time to prepare for the Practitioner exam.
• First, go through and finish all the videos provided by the online training centers.
• Buy some sticker tabs and put them on your Prince2 manual. Put one sticker tab per section (starting from chapter1,chapter2.... up to glossary). 
• At the end of the manual, I suggest you draw the Prince2 Process Model (it will clearly show you the flow of the processes, which products are created/updated on which process). Try searching for some Prince2 Process Model on the web.
• Read some sample papers and do some exam simulator practice.
• Same with foundation, be aware of the structure of the questions. Multiple choice with 1 or 2 answers, sequences, reason-assertion, matching type.
• Do some reading on the Appendix A as you will be required to know the sections of the documents (e.g. Business Case, End Project Report, Configuration Item Records).

During Practitioner Exam:
On taking the Practitioner exam, you will be given 2.5 hours maximum. But it can be finished earlier (I finished mine around 1.5 hours). During the exam, they will allow you to take 5 minutes break (although I didn't take any breaks during my exam).  Before you begin the exam, they will ask you if you would like to print the exam scenario and please PRINT IT so that you won't need to flip back-and-forth on the scenario and questions page. Since you already have the project scenario printed, you can concentrate on the questions.  Also bring some water, some light snacks (peanuts,sweets) as the 2.5 hours will be intense. Again, don't leave any blanks as there are no negative markings.

Good luck!