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60 lines
2.6 KiB
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60 lines
2.6 KiB
Markdown
# Octopus Flex PCB (SulaJalmari)
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nRF52840-based flex PCB project with a shape of an octopus. Because why not. You can read the story from [final.md](final.md).
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<img src="pics/device_diagram.png" height=800>
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## Hardware specs
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* **Board Structure:** 2x Flex PCBs (acting as the octopus head and legs) and 1x FR4 PCB (acting as the base board).
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* **MCU:** nRF52840-QIAA (soldered directly to the flex PCB with a stiffener on the reverse side).
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* **IMU:** ICM-20602 accelerometer (shares an interrupt line with the light sensor).
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* **Light Sensor:** XYC-ALS21C-K1 I2C ambient light sensor (shares an interrupt with the IMU).
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* **Leg LEDs:** 8x Blue LEDs running at 2mA (LED0603-RD).
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* **Eye LEDs:** 2x Addressable RGB LEDs (WS2812B-2020).
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* **Power & Battery:** TP4054 50mA battery charger, ME6211C22M5G-N 3V3 LDO, and XC6206P362MR 3V6 LDO (dedicated to the addressable LEDs).
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* **Connectivity:** Bluetooth with a minimal PCB trace antenna, USB-C for power/programming/serial, and a 5V rail to chain multiple devices together.
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* **Audio & Haptics:** Buzzer with a driving transistor, plus a footprint for a vibration motor (motor ultimately not installed in the final version).
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* **Interface:** 2x tactile user buttons, 1x tactile reset button, and an on/off switch.
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* **Debugging:** Base board debugging pins compatible with a standard ~$3 DAPLink debugger via pyOCD/OpenOCD.
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* **Aesthetics:** Silkscreen suction cups and mouth.
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> Schematics and gerbers are under [Hardware/V3](Hardware/V3)
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<img src="pics/smack.gif">
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## Fun facts
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### Fun Things
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* Because the assembled PCBs take the physical shape of an octopus, the whole device wobbles when shaken.
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* When the device is wobbling and the LEDs are running PWM, the movement actually allows you to see the PWM cycle with your naked eye.
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* The IMU is mounted in the very top of the head. This means you can tap the top of the device, and the accelerometer registers it as a physical button press.
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### Flaws
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* During "stress testing" (read: repeatedly slamming it against the base board), some of the MCU pins eventually detached. Please don't torture the electronics!
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* The vibration motor was mostly unnoticeable, leading to its removal from the final assembly. (Pins to connect a motor still exist)
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* Transporting an assembled device safely is tricky.
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## Software
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> Checkout [chill](https://git.aintmina.org/aintgit/chill) project for building zephyr app with MCUboot.
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## History
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### Idea
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Paper cutout with magnet connections.
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<img src="pics/paper_model_v1.jpg">
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### First prototype
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<img src="pics/prototype1-3.jpg">
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### Second prototype
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<img src="pics/Device1.jpg">
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### Final version
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<img src="pics/final_device.jpg"> |