Phendrana

Features

• Longer Battery Life
• Multiple Bluetooth Connections
• Single-colour Backlight
• Cherry MX and Kailh Choc compatible
• Swappable Switches, Battery, and MCU
• 3D Printed Case

Skills Learned:

• Embedded Systems
• PCB Design (KiCAD)
• C/C++
• Zephyr (and Zephyr Mechanical Keyboard)
• Lithium Batteries
• Power Management
• Power Regulator Design
• I2C
• LEDs
• 3D Printing

Firmware

Firmware can be found here on the Github Repo

To compile the firmware:

Before flashing, ensure the .UF2 bootloader is installed. It should be version 0.7.0, which can be downloaded here

The file should be named "nrf52840_m2_bootloader-0.7.0_s140_6.1.1.hex", if the M.2 is bought seperately, you will need the Makerdiary Developer Kit Dock to upload it

• Download the Phendrana Firmware repo
• Follow the ZMK Toolchain Local Build Setup Guide
• Place the Phendrana files in the zmk/app/boards/shields/phendrana folder (you will need to make the folder)
• It should look like below:
• 
• Open the zmk/app folder in terminal
• Use the command "west build -b -p nrf52840_m2 -- -DSHIELD=phendrana_left" to build the left half firmware
• Use the command "west build -b -p nrf52840_m2 -- -DSHIELD=phendrana_right" to build the right firmware
• Upload both firmwares, to their respective halves, attempt to powerup at a similar time (The halves should automatically connect to each other)

Inspirations

• The Sanctuary
• ZMK
• Quefrency

Hardware

Currently the Hardware files are not released. The 3d case files are intended to be released at one point, however I wish to fix the files first, and provide more files for different versions of Phendrana.

KiCAD/Gerber files likely won't be released, and neither would the BOM. This is because it wasn't really designed to be built by others, and I'd want to do a complete overhaul if others were to build one. If you'd like Phendrana, contact me

Parts Needed

• Choc V1 Keyswitches
• Any Choc V1 Low Profile switch should fit
• 85 Switches needed, recommended to buy 90
• Choc Keycaps
• Other keycap sets work, but this keyboard is specifically designed for this set. Other sets or individual keys will create gaps between keys
• Choc Stabilizers
• 6x 2U Stabilizers needed, recommended to get the "8 sets"
• BL-5C Battery
• Ensure the size is over 1000mAh
• USB-C cables
• Any USB-C to USB-A cable should work. USB-C to USB-C cables will not work

Versions

Rev 1.0.0 - Initial Release - Small errors, requiring 1 wire for USB connection, as well as other small wires to fix small trace errors

Rev 1.0.1 - Unreleased - Fixes errors from Rev 1.0.0

Instructions

Partial instructions for Phendrana exist, however complete instructions to build from scratch are unavailable.

Can I buy this?

Currently a few Phendrana's have been given to friends, from extra parts I had when making my own. I do not really intend to sell them.

For various reasons, I won't sell them. I can only really sell a PCB and BOM. If you have SMD skills, and want one, get in contact. Please note that prices are subject to change, and lead times may be long (likely about a month).

Notes

Phendrana is a keyboard that attempts to follow the ZMK design language. This introduces a few unique features to the board, that may be odd the first time used. These are:

• Power, there is no outside power switch for Phendrana, it relies on sleep modes to save power
• Internally there is a power switch, however it was designed as more of a power switch for long transport
• Phendrana has two sleep modes:
• Idle - LEDs turn off, keyboard is still connected (~30s after you've stopped typing)
• Sleep - Keyboard disconnects from devices to save power from Bluetooth (~15m after you've stopped typing)
• These timings can be changed in the .conf files (for left and right), using these parameters: https://zmk.dev/docs/config/power#idlesleep
• Phendrana can be used either through USB, or Bluetooth, if connected to a PC using USB, it will always send keystrokes to the PC through USB
• You should still be able to charge while using Bluetooth, you just would need to use an AC adapter to do so
• It should be noted that Phendrana won't work with USB C-C cables

Default Key Combinations

• CAPS Lock (Labeled " Del" due to key sizes) and Function
• Modshifts, if tapped, CAPS acts as CAPS Lock, Fn acts as Right Windows
• Layer 1:
• F1-F6 change Bluetooth input (use this to connect multiple PCs)
• Windows removes ("forgets") Bluetooth pairing - remove from client side when you do this
• Volume Down changes to mute
• Left/Right arrow change to Previous/Skip music
• ESC turns off LEDs
• Tilde increases LED Brightness
• Tab decreases LED Brightness
• Other layers are not currently implemented, however could be added

LED Functionality

Power LED functionality is listed below:

• Green (Top): Power Good, if power is connected, this LED is on
• Red (middle):
• If battery is connected, LED is on for charging, off when charge is complete
• If battery is disconnected, this LED is high impedance (it will flicker at a lower brightness)
• Red (bottom):
• If battery is connected, LED is on when charge is complete (off when charging)
• If battery is disconnected, the LED is on

Troubleshooting

• Stabilizers Bind:
• Check that Stabilizers are installed evenly
• Check if there is a screw beside the stabilizer, if so, loosen screw
• Bluetooth not connecting:
• Reset Master (Left) PCB (Reset switch, ESC+CAPS+CTRL, or remove battery)
• Right side isn't connecting:
• Remove batteries from both sides, and install batteries close to the same time
• If problem persists, use "Settings_reset.uf2" on both sides, then upload "PhendranaL.uf2" and "PhendranaR.uf2" to the respective sides
• One side starts blinking lights
• Battery is on the edge of dying, and needs to be charged (happens due to the battery protection IC)

Default Phendrana bindings, and Settings_reset can be downloaded here