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[Flipper Zero] refuse Raspberry Pi, make our own board from scratch. Finding the right WiFi chip



Flipper Zero is a pocket multitool project for hackers in the tamagotchi form factor, which I am developing with friends. Previous post [1] .

A lot has happened since the first post about flipper. We worked hard all this time and the project has undergone radical changes. The main news is that we decided to completely abandon the Raspberry Pi Zero and make our board from scratch based on the i.MX6 chip. This greatly complicates the development and completely changes the whole concept, but I'm sure it's worth it.

Also, we still have not found the correct WiFi chipset, which supports all the necessary functions for WiFi attacks, while supporting the 5Ghz range and has not been outdated for 15 years. Therefore, I invite everyone to participate in our study.

In the article I will tell you why we made such a decision, at what stage the project is, current tasks, and how you can take part.


What is bad Raspberry Pi Zero



I personally adore the Raspberry Pi, but during the development process it turned out that it sucks for many reasons. The most commonplace - you can’t stupidly buy it. Even large distributors have no more than a couple of hundred rpi0s, and stores like Adafruit and Sparkfun sell no more than 1 in their hands. Yes, there are several factories that produce rpi0 under a license from the Raspberry Pi Foundation, but they also cannot ship batches of 3-5 thousand each. It looks like that rpi0 is sold at a price on the verge of cost and is more aimed at popularizing the platform.

Here are the main reasons for abandoning rpi0


  • . Farnell Compute Module. Alibaba , . , , , - 5 , .
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  • BCM2835, rpi. .
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  • WiFi.
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The Raspberry Pi Foundation itself proposes to use the RPi Compute Module for such tasks. This is a board in the form factor of the SO-DIMM module (like RAM in laptops), which is inserted into the motherboard. This option does not suit us, since it greatly increases the size of the device.

Raspberry Pi Compute Module - a board in the form factor of the SO-DIMM module for installation in your device

Then we started looking at different SoMs (System on Module), the most attractive looking modules based on i.MX6. All our searches are described in the topic on the Raspberry Pi Zero Alternatives forum.. But you need to keep in mind that not all companies will be ready to work with you with volumes even of 3-5 thousand units per year. For example, the Israeli Variscite simply stopped responding to us when it found out the planned procurement volumes. Apparently, they are not only interested in selling SoMs without additional services in the form of support and integration. I would also like to mention the Russian developer Starterkit.ru , who make very interesting devices, like SK-iMX6ULL-NANO . They are almost impossible to google, and I would not have known about their existence if my friends had not told me.

As a result, comparing all the options and considering the economy, we made a difficult decision to make our SoM from scratch especially for Flipper based on the i.MX6 ULZ chip. This is a single core Cortex-A7 with a frequency of 900 MHz with almost the same performance as rpi0, while it is almost cold under load, while rpi0 heats up like a stove.
Making our motherboard from scratch, we have complete freedom in the arrangement of elements on the motherboard, which is why we expect to get a more compact device. i.MX6 ULZ is a stripped down version of i.MX6 ULL without some interfaces and a video core, so for development we use the MCIMX6ULL-EVK devboard with the i.MX6 ULL chip, just not using part of the interfaces. This board, by the way, is supported by the mainline linux kernel, so Kali Linux with the kernel from the packages is loaded on it.

Here is what flipper without clothes looks like at the moment:


Correct wifi


Hacking WiFi is one of Flipper's main features, so it is extremely important to choose the right WiFi chipset that will support all the necessary functions: packet injection and monitor mode. At the same time be able to 5GHz range and modern standards like 802.11ac. Unfortunately, such chips could not be found right away.

Chinese SiP module (system in package) Apmak AP6255 based on BCM43456

Now we are considering several candidates, but all of them require finishing and it is not yet known which one is better to choose. Therefore, I really ask everyone who understands WiFi poke to join our search here: Wi-Fi chip with SPI / SDIO interface that supports monitoring and packet injection

Key candidates:



Please carefully read the requirements on the forum, including the connection interface, before advising something. Remember that I have been carefully studying this topic for several months and have already shoveled everything that can be found.


What is ready




The entire part for which STM32 is responsible is already working: 433Mhz, iButton, read-emulation 125kHz.
The mechanical part, buttons, case, connectors, layout are now under active development, the video and photos below have an outdated case, there will be more joystick in new versions.

In the video, a simple demonstration of the opening of the barrier using a replay of the remote control signal.




FAQ



How to buy?


Presumably, the crowdfunding campaign on Kickstarter will be launched in April-May of this year. We hope to send finished devices six months after the completion of the collection. If you are interested in the device, I ask you to leave your mail at the bottom of the site , we will send offers to subscribers when prototypes and early samples for sale are ready.

It is legal?


This is a research tool. All its components can be purchased separately at the store. If you build in a WiFi adapter and a 433MHz transmitter in a small case and add a screen there, it will not become more illegal from this. The device does not fall under the definition of special. means or device for secret collection of information. It can be illegal to use it ONLY for the purpose of causing damage or for illegal actions. In other words, I can make knives of any shape and from any metal, the responsibility for using my knives lies with you.

How to embed?


At the moment, you can personally support me with small donations for food through Patreon . Regular donations in the form of $ 1 are much better than a large amount at a time, because they allow you to predict ahead.


I publish all the notes on the project in my Telegram channel @zhovner_hub .

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