Now you can show off your inner tech genius with your own Project Mc² Smart Pixel Purse (sold separately). This easy-to-use app allows you to create your own images, animations, and stylish.

The disassembly of a pretty trivial toy got a bit out of hand. :-)

ApkLizard Editor's Team Note (Android Project Mc2 Smart Pixel Purse 1.0.20) Project Mc2 Smart Pixel Purse Game is developed by MGA Entertainment and published in Casual category on 2020-01-30. Project Mc2 Smart Pixel Purse 's latest version is 1.0.20. According to our rating team, Project Mc2 Smart Pixel Purse 's rating score is 3 / 5. Project Mc2 ADISN Electronic Journal - here's our review of the spy journal which contains a secret locking mechanism and lets you hide your precious things, including your mobile phone. Write secret messages and work on case files via the Project Mc2 IOS app - join McKeyla McAlister's team! Inside the bag is a compartment where you can slot in and connect up a smartphone and using the Project Mc2 App you can create and download your own designs to display. As with all of the Project Mc2 dolls and toys, the Pixel Purse has been designed not only to be a fun toy but also to encourage an interest in science, maths, engineering.

It started with this:

A useless gizmo for only $6.16 where one part is worth more than the whole thing combined?Irresistable!

The next day this abomination arrived:

Calling this a purse is a stretch. It’s piece of hard plastic that only looks the part. Barely.

But it’s all about the LED screen on the other side:

Taking pictures of a scanning LED display with the scanning camera of an iPhone doesn’t work very well. In the realworld, your eyes should see a solid image.

Project Mc2 Pixel Purse App

The purse comes with a bunch of built-in patterns and animations. You can create new ones through an iPhoneor Android app.

There are teardown videos on Youtube, but it’s super simple: justa matter of removing a bunch of screws.

So what can we find inside? It’s really very simple:

4 AA batteries
A 3-way power switch
A button to switch between patterns
a P6 32x16 LED panel
the main PCB with all the electronics
audio plug to download images from your phone to the purse

A P6 panel has an LED pitch of 6mm. Multiplied by the number of LEDs that gives 192mm x 96mm.

This panel is the reason why this purse is such a good deal: on Adafruit, it sells for $25. On AliExpress, you should be ableto find one for ~$14 including shipping.

The panel has a standard HUB75 interface with 3 row address lines.

With 3 address lines you can select 8 rows. With 2 parallel RGB shift register inputs, you end up with 16 rows, just what you’d expect for a 32x16 panel.

Important: The 2 upper address lines D and E are not floating, but tied to ground. You need to double check when connecting this panel to a generic HUB75 driver that these pins are not driven to avoid a short-circuit condition!

Unfortunately, the panel only has a HUB75 input connector, but the output connector has been left unpopulated.

If you want to daisy chain multiple panels, you’ll have to solder a connector yourself.

The controller PCB is spartan, with the following major components:

microcontroller
The microcontroller is buried under a blob of hardened plastic. Nothing is known about it.
4Mbit SPI PROM
XinCore F40A-104GIP
DC/DC converter
AP3502E - 340kHz, 2A Synchronous DC-DC Buck Converter
HUB75 connector
32.768kHz Xtal

There are connectors to switches, battery power, and to feed a regulated 5V to the LCD panel. Butthere’s also an unused connector with I2C and ‘VPP’ labels. There’s little doubt that these are usedto program the microcontroller during production.

I hoped to be able to repurpose the whole board by reprogramming the microcontroller firmware, soI dumped the traffic of the SPI during operation.

In the past, wiring up the small IO pins of the SPI PROM would have been enough of a hassle to justnot bother, but with my micro clips (see my review here),it takes just a few minutes to do that:

Connect it to a Saleae logic analyzer, and you’re good to go!

The overall SPI activity profile from initial powerdown (pressing the front button) to complete power downlooks like this:

It takes about 1s to go from powering up the SPI IO pins to traffic. This traffic continousas long as the LED panel is lighted up. After 30s, the traffic stops, and another 30s later,the SPI IOs power down.

When you zoom in, there is constant repetition of a burst followed by an idle phase.

The period of this repetition is 250ms, or a 4Hz. That’s way too slow for a single refresh of theLED panel, so I think this is the rate at which the purse cycles between different frames of ananimation.

The microcontroller has probably enough memory to store a single 32x16 pixel image, but loads thedata for a different image on-demand.

This theory didn’t really last long when I looked at the SPI data for a case where I rotate between3 different animations. The first and the third one behave as expected, with a pattern repeatingat 4Hz.

But the middle pattern does not, and is much busier:

There is a somewhat repeating pattern every ~48ms.

I didn’t go any deeper into analyzing the exact format in which the frame are stored in the SPI PROM.

Unfortunately, the SPI dump does not contain anything that looks like a firmware. That removes muchof the hope to rewrite the firmware for our own purposes.

It might be possible to capture the firmware through the I2C programming interface, but I did nottry that.

I also wanted to see if there was anything special about the signalling on the HUB75 interface.

Looking at another Saleae capture, you can see that there’s repeating pattern with an overall period of15ms. That’s the overall screen refresh rate. During this time, the 3 address lines rotate throughall 8 combinations, thus refreshing all the rows of the panel.

15ms for 8 addresses means 1.875ms per address.

Zooming in to a single address phase, we see the following:

There are 4 phases (marked red, green, blue and yellow), each double the duration of the previous one.

During each phase, the clock is toggled 32 times: the number needed to shift in all the 1-bit RGBvalues for each LED of the address row.

However when you look at the rectangle in cyan, color values are only shifted in during the shortestphase. During the other phases, zeros are being shifted into the column drivers.

What’s happening here is the following: the microcontroller firmware was designed to support 16 colorshades per pixels, hence the 4 phases of increasing duration. However, the pixel purse only supportsimages with 8 colors: the primaries R/G/B are either on or off.

Those primaries are assigned to the LSB of the 4-bit color shade. This has a major benefit thatthe LEDs are only driven 1/16th of the normal row active time of 1.875ms, thereby saving a considerableamount of power. Even this low ON duty cycle is sufficient for the pixel purse: it doesn’t need thelight output of an LED panel that was design for huge video walls.

To learn more about driving LED panels with a HUB75 interface, you should read this excellent article on Sparkfun.

I was particularly interested in how images are uploaded through the audio interface. The overalprocess is simple: you enter a new image on an iOS or Android app, you insert audio plug in yourphone or iPad, and off you go.

It’s a much system that doesn’t require any complex protocol like USB and thus very cheap toimplement.

Mc2 Pixel Purse App

The overall process looks like this:

Here, uploading takes about 7s, but that’s for an animation with multiple images. (A single imagetakes only 1 second.) When not uploading, the iOS app sends a heartbeat pulse every 2 seconds.

The heartbeat pulse shows how data is encoded:

Mc2 Purse App Image

The encoding seems to be using ON-OFF keying.

In the image below, you see how 2 consecutive ‘1’ bits are encoded. It takes 1.2ms for the 2of them, so we have a transfer BW of 0.6ms per bit or 1.6kbps. 0.6 x 32 x 16 x 3 = 0.9s, which corresponds nicely with the time to transfer 1 image.

I tried to follow the signal path of the incoming audio signals all the way to the microcontroller.The last point I could find was this one:

At that stage in the proce