DCC Light Board for Kato EMUs

This is the description of an experimental project of mine: A DCC interior light board compatible with Kato's N-gauge EMUs.

Summary of the project:

• DCC Light Board based on the Microchip ATtiny1616 MCU
• DCC tested from 12V to 18V
• Energy storage / Antiflicker / Keep Alive: 1200uF
• Programmable light brightness with LED luminance table
• Programmable CCT (Correlated Colour Temperature), continuously between 3000K (warm white) and 6500K (cool white), using two sets of 8 LEDs: 8 x 3000K and 8 x 6500K
• Two sets of parameters Light brightness, CCT and Function Control, for day / night modes

This is a photo of the light board (manufacturing and paneling by JLCPCB.com). I have used white, just 0.4mm thick FR4 PCB, so the whole board is quite flexible. The size is 125 mm x 77 mm.

For connection to the rail / DCC, I have made a small PCB bracket that I solder perpendicular to the light board. That bracket takes the place of the standard Kato light kit and no modification of the trains is necessary.

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The source code for the ATtiny1616 and the board's files are available here: https://github.com/madsing98/DCCInterLight1616. DCC signal decoding is provided by the NmraDcc library (https://github.com/mrrwa/NmraDcc). 

This is the CV map:

Programming
The ATtiny is programmed using UPDI. Just three pins are necessary, VCC, GND and UPDI. I have built a programming adapter using a standard clamp fixture and pogo pins, all available from AliExpress here: https://www.aliexpress.com/item/1005006888442559.html 

This is what the adapter looks like:

I am happy with the results. Being to customise the light brightness and colour temperature using CVs is extremely confortable. These are a few photos of the same train fitted with the light board set at various brightness / colour temperature settings.