Raspberry Pi And ESP32-S2 Team Up For MutantC_V4

Back in 2019 we first came across the mutantC, an open source 3D printable Raspberry Pi handheld created by [rahmanshaber] that took more than a little inspiration from Sony’s VAIO ultra-mobile PCs (UMPCs) from the early 2000s. It was an impressive first effort, but it clearly had a long way to go before it could really be a practical mobile device.

Well after two years of development and three iterative versions of this Linux powered QWERTY slider, [rahmanshaber] is ready to show off the new and improved mutantC_v4. Outwardly it looks quite similar to the original version, with the notable addition of a tiny thumbstick and a pair of programmable buttons on the right side that can be used for input in addition to the touch screen. But inside it’s a whole other story, with so many changes and improvements that we hardly even know where to start.

Inside the mutantC_v4, showing off the ESP32-S2

Probably the most notable improvement is the addition of an ESP32-S2, specifically a bare ESP-12K module, to the main PCB. Previous versions of the hardware used an Arduino Pro Micro to interface with all the hardware, but the added horsepower of the ESP32 should come in handy with the array of sensors, controls, and NeoPixels that [rahmanshaber] has tasked the chip with. There’s even a buzzer and a coin-style vibration motor in there to provide some feedback to the user. While the board has changed significantly, it still retains compatibility with the Pi Zero, 2, 3, and 4.

Another notable addition is the expansion connector on the bottom of the handheld that has pins for I2C, UART, and 3.3 V. In the video below, [rahmanshaber] mentions that this feature was previously implemented with a standard 2×6 female header block, but is now using a far slimmer female USB-C port. We do wonder if it’s not a bit confusing to have this faux-USB port right next to the real one that’s actually used to charge the system, but with such cramped quarters occasionally you’ve got to make some tough decisions like that.

It’s quite inspiring to see how [rahmanshaber] has honed his skills since releasing the first version of the mutantC. The 3D printed parts and PCBs have matured considerably over the last two years, showing how quickly a dedicated hobbyist can advance their abilities. The most recent version has been entered in the 2021 Hackaday Prize. But the show isn’t over yet, as we hear v5 of this impressive handheld may tackle the Raspberry Pi 4 Compute Module.

12 thoughts on “Raspberry Pi And ESP32-S2 Team Up For MutantC_V4

  1. Yes, I saw this a few days ago, and I thought repurposing a USB-C socket was a bad idea. Apart from that it’s a great implementation and I think I might make one (because I can!)

    1. wow! psion 5 linux! i used to have a psion revo, i really loved it though i hated developing for symbian. crazy that years after it went out of date, people bothered to get linux to run on it :)

  2. The worst part is that there are two of them next to each other with incompatible use, one of them is for USB charge and one is for a docking station. I told him that this is not a good idea, but he insisted on doing so.

  3. The main problem here is the Raspberry, it’s not supposed to be used in portable devices. The firmware for the GPU does not support suspend at all, so the machine cannot get into a sleep when it’s not used as smartphones do, etc. At least v3 and v4 can turn off the display, which will save power if you want, for instance, play music.

  4. This is a really tidy project, it has been great to see the evolution of the design since V1. The writeup suggests that there might be a V5 that uses the Compute Module? Any more info on this? It would be my dream DIY handheld… I was actually just reading the original entry from 2019 and saying it would be great to see a version to suit the Compute Module!

    Thank you to [rahmanshaber] for sharing all the work so far – anyone who has tried to share a project like this will know just how much effort goes into describing the work.

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