Reverse engineering a Imagotag retail 2.6 RED NFC - 2

Sorry for the delay but I had a lot of exams recently, such as Signal Recovery, Microcontrollers and Biochip.
I finally managed to work on the Imgotag project!

Suggested music: 
PostmodernJukebox - Seven Nation Army (ft. Haley Reinhart)

Robin Schulz - Sugar (ft. Francesco Yates)

Part 2

The Complete Circuit

In the last week I spent long hours on Photoshop, following traces and comparing the circuit layout with the datasheet diagrams, and now I have a clear view of what is going on.

If you want to feel the same thrill I had, here you have the datasheet files and the aligned Photoshop image:

DOWNLOAD ZIP FILE

The board is really similar to this datasheet diagram, but peeking through the PCB layers I discovered that there are some differences in pins 5 to 8, connected to other capacitors or power rails, probably they had their custom EPD made.

Still, there is a thing that I can't figure out: It is obvious that this board has A LOT of unused space, and this is a plus, as it adds flexibility to accommodate late changes or different variants, but why did they do this:

We have two pMOS in series, the second one retarded with an RC lowpass.

Simply put: it takes a little more time to switch the second transistor on.

I understand the need for an RC to limit the inrush current: coin cell batteries are known for having high series resistance; not having a "soft start" protection might bring the Vdd too low and trigger the brown-out of the MCU!

But why TWO pMOS?  If it wasn't an obliged choice or a mistake, I have no idea.

Reverse engineering a Imagotag retail 2.6 RED NFC - 1

In this blog post series I will describe my attempts in reverse engineering an electronic price tag to make a little ebook or a pager out of it..

Suggested Music:
Cory Henry - Billy Jean (cover)        Electro Deluxe - Home (album)

This project is intriguing me because of the many things I am learning and the endless possibilities that E-ink displays give.

Some abbreviations i will use:

EPD: Electronic Paper Display
PCB: Printed Circuit Board
MCU: Micro Controller Unit

A short Introduction

Good evening everyone!

I am an Italian electronic engineering student and consultant.

I am really enthusiast about electronics, sound engineering, repairing things and tearing stuff apart to understand the inner working.

Other interests include cycling and cooking, but i don't consider myself "pro" at them

This is my brand new blog, I will post fresh content whenever possible, so bear with me for tear-downs, projects, repairs, and much more!

These are my social channels: YouTube Twitter 

-Eponge