LKP Core

LKP

レンくんピアノ (Len-kun Piano)

Capacitive touch slider controller for rhythm games.

Contents

pcb/LKP-Core

Microcontroller board for use with LKP electrode boards. Supports up to 32 channel of self capacitance input. Includes a WS281x LED driver channel with protection resistor. Supports I2C or UART as communication methods.

For sample firmware for use with LKP-Core, see LKP-FW.

Pin mapping

I/O port:

WS281x LED connector:

SWD connector:

pcb/LKP-Core-EasyAccess

IMPORTANT: WS281x LED driver will not work on this variant. See errata. This variant is only included for documentation purposes and will no longer receive updates.

A variant of LKP-Core that originally focused on improved accessibility for arcade controller DIY hobbyists with only basic (through hole) soldering skills. All parts used in this variant (once the chip shortage situations improve) are available for use with JLCPCB Assembly service, thus enables the possibility of ordering fully assembled and working boards straight from JLCPCB. Even without the assembly service working at the moment, the chip used in this variant can be purchased from LCSC in low quantity for a lot less money compare to the original chip on Digi-key, so it also acts as a budget option without sacrificing performance in significant ways.

pcb/LKP-Diva-Electrode-Tile

Electrode board for Project DIVA Future Tone slider controller. Works as a 2-tile setup. Both tiles use the same design, with right tile being a 180 degree rotated version of the left tile.

pcb/LKP-Chu-Electrode-Tile

Electrode board for Chunithm slider controller. Works the same as its LKP-Diva counterpart.

pcb/LKP-IF-QC

I2C quick connect (compatible with SparkFun Qwiic® and Adafruit STEMMA® QT) interface for LKP-Core. Goes up to 1MHz for I2C connections and up to 24MHz for UART connections. Converts between 5V logic used by LKP-Core and 3.3V logic used by Qwiic®/STEMMA® QT.

It is also possible to use it to convert UART signal for main microcontroller running between 1.65V and 3.6V. To set it up:

1. Break out the signals on any one of the Qwiic®/STEMMA® QT port on LKP-IF-QC using a Qwiic®/STEMMA® QT breakout board.
2. Connect the 3.3V pin to microcontroller's I/O voltage reference (must be between 1.65V and 3.6V).
3. Connect SDA (blue wire, UART TX) to RX and SCL (yellow wire, UART RX) to TX.
4. The other Qwiic®/STEMMA® QT port should be left unconnected.

Note that although the low side of the level shifter can take any voltage between 1.65V and 3.6V, 3.3V must be used in order to maintain compatibility with other Qwiic®/STEMMA® QT-compatible systems.

BOM

LKP-Core

• C1, C4, C6, C10: Generic 1uF 0603 X5R ceramic capacitor. (I used CC0603KRX5R8BB105)
• C2, C3, C5, C8, C11: Generic 100nF 0603 ceramic capacitor. (I used CL10B104KA8NNNC)
• C7: GRM2195C1H103JA01D.
• C9: GCM1885C1H222JA16D.
• C12: Generic 10uF EIA-3216-18 tantalum capacitor.
• D1: Generic SOD-123 Schottky diode (MBR0520L).
• D2: Generic 0805 LED (yellow color).
• FB1: Generic 0603 ferrite bead (330ohm@100MHz).
• J1, J2: Straight female .1" header 2x9.
• J3: JST PH 2 positions.
• J4: Straight male .1" header 1x4 (can be angled if not using LKP-IF-*).
• J5: Straight male .1" header 1x5 (can be angled if not using LKP-IF-*).
• J6: Angled male .1" header 1x2.
• R1: Generic 1kohm 5% 0603 resistor.
• R2: Generic 470ohm 5% 0603 resistor.
• R3, R4: Generic 560ohm 5% 0603 resistor.
• RN*: Generic 560ohm 5% 0402x4 convex resistor array (I used 4D02WGJ0561TCE).
• U1: CY8C4246AZI-M445 (or CY8C4247AZI-M485, Needs minor firmware modifications).

LKP-Diva-Electrode-Tile and LKP-Chu-Electrode-Tile

• J1: Straight male .1" SMD header 2x9 (without bumps at the bottom).
  • This can be hard to find. For small scale DIY manufacturing try searching "pin header double smd" on aliexpress.

LKP-IF-QC

• C1, C2: Generic 100nF 0603 ceramic capacitor. (I used CL10B104KA8NNNC).
• D1: Generic SOD-123 Schottky diode (MBR0520L).
• J1, J2: JST SH SM04B.
• J3: Straight female (10.5mm stacking or regular) .1" header 1x5.
• J4: Straight female (10.5mm stacking or regular) .1" header 1x4.
• J5: Straight or angled male .1" header header 1x2 (Optional if using stacking headers for J3-4).
• U1: TCA9406DCTR.

Powering

By default LKP expects 5V power. Using lower supply voltage down to 1.8V is possible by modifying the power specs in LKP-FW and adding a level shifter module to the WS281x driver pin (labeled as LED on board). Reference voltage for I/O can be approximated by tapping into the VTARG pin on the SWD port.

Known issues / Erratas

• (LKP-Core v1.0) The reverse voltage protection diode (D1) does not protect C12. Proceed with caution when connecting the power to make sure the polarity is correct.
• (LKP-Core v1.1) When used with LKP-Assy, connector J4, J5 and J6 may collide with the bottom of LKP-Assy. A workaround would be soldering all the specified connectors on the back side of the PCB instead. Also, when using LKP-IF-Qwiic, J4 and J5 must be soldered on the back side.
• (LKP-Core-EasyAccess v1.2-E) Due to an oversight when choosing chips for this board, it lacks the necessary hardware features for the WS281x driver pin to function (i.e. UDB). A software workaround might be possible (with e.g. SPI DMA like FastLED Arduino library) but it might not be cost effective to develop it further.

Special thanks

• @pol8139's controller build guide for pointing me to PSoC as a potential solution and demonstrating the possibility of using a single PSoC 4 to drive the entire slider.
• @azhao12345 for providing the idea of modular and tiled electrode design.
• ryun and @somewhatlurker for their reverse-engineering effort on 837-15275/15330 protocol and firmware, which form the basis of LKP-Serial and sega-slider.md.
• MarkH_61 for StripLightLib, which saved me quite a bit of headache of figuring out how to use UDB/datapath to drive huge array of NeoPixels without starving the CPU.