2 layers70 × 70 mm
E24-receiver board
mikesmitty/rp24-dcc-decoder
DIY DCC decoder for model railroad locomotives in an E24 form factor, powered by an RP2350 (Raspberry Pi Pico 2)
307 parts12
6 layers70 × 70 mm
Rp2350-decoder
mikesmitty/rp24-dcc-decoder12DIY DCC decoder for model railroad locomotives in an E24 form factor, powered by an RP2350 (Raspberry Pi Pico 2)
- Size
- 70 × 70 mm
- Copper layers
- 6
- Thickness
- 0.85 mm
- Parts
- 543
- Nets
- 328
- Pads
- 1,675
- Tracks, vias
- 3,984, 692
- Pours
- 92
- Routed
- Yes
- KiCad
- KiCad 9.0 (file 20241229)
- Created
- 11 Jan 2025
- Updated
- 7 Nov 2026
Overview
Rp2350-decoder is an open-source printed circuit board by mikesmitty, from the mikesmitty/rp24-dcc-decoder repository on GitHub. It is a 6-layer board of 70 × 70 mm with 543 parts on 328 nets, routed with 3,984 tracks and 692 vias.
It is built around the RP2350A, AP63203WU and MAX98357AEWL+T, with the MD9927, W25Q128JVPIQ and DMN2991UDA-7B among its other parts. Its parts include 76 capacitors, 76 resistors, 36 diodes, 32 transistors and 24 ICs. It belongs with the RP2350 boards of this library.
Main components
11
RP2350A
QFN-60-EP(7x7)Power-on reset (POR)、Undervoltage detection (BOR/LVD/LVR/LVI)、Watchdog reset、Integrated LDO、True random number generator (TRNG)、Hardware ECC check QFN-60-EP(7x7) Microcontrollers (MCU/MPU/SOC) ROHSRaspberry PiMicrocontrollers (MCU/MPU/SOC)
AP63203WU
TSOT-23-6-40℃~+85℃@(TA) 1 1.1MHz 22uA 2A 3.3V 3.8V~32V Buck Built-in Fixed Overcurrent Protection、Light load efficient mode、Cycle-by-cycle current limiting、Hiccup current limiting、EMI optimization (spread spectrum) Step-down type Yes TSOT-23-6 DC-DC Converters ROHSDiodes IncorporatedDC-DC Converters
MAX98357AEWL+T
BGA-9(1.3x1.3)-40℃~+85℃ 0.015% 1-Channel、2-Channel 2.5V~5.5V 3.2W×1@4Ω、1.8W×1@8Ω、0.93W×1@8Ω 3.35mA 77dB 92% Automatic mute/no-noise switch、Enable/shutdown function、Filterless architecture、Analog voltage gain、Automatic power-saving mode Class D BGA-9(1.3x1.3) Audio Amplifiers ROHSMaxim Integrated (Analog Devices)Audio Amplifiers
MD9927
WDFN-8-EP(2x2)-40℃~+85℃ 1 1.8A 1.8A 1.8V~7V 120nA 500mΩ Yes WDFN-8-EP(2x2) Brushed DC Motor Drivers ROHSShanghai Mingda MicroelectronicsBrushed DC Motor Drivers
W25Q128JVPIQ
WSON-8-EP(5x6)-40℃~+85℃ 100,000 cycles 10uA 120ms@(32KB) 128Mbit 133MHz 2.7V~3.6V 20 Years Power-on reset、Hardware write protection、Software write protection、Write enable latch、Absolute write protection、Power lock protection SPI WSON-8-EP(5x6) NOR FLASH ROHSWinbond ElecNOR FLASH
DMN2991UDA-7B
X2-DFN0806-6-55℃~+150℃ 2 N-Channel 20V 21.5pF 3.7pF 310mW 350pC@4.5V 4.9pF 450mA 630mΩ@2.5V 780mV N-Channel X2-DFN0806-6 MOSFETs ROHSDiodes IncorporatedMOSFETs
LMBR4020H3T5G
DFN1608-2-55℃~+125℃ 1 Independent 12A 2A 40V 50uA 560mV DFN1608-2 Schottky Diodes ROHSLeshan Radio (LRC)Schottky Diodes
AP1606
DFN-3L(0.6x1)-50℃~+150℃ 1 N-channel 1.1nC@4.5V 1.2V 15pF 20V 260mΩ@4.5V 40pF 550mW 6.5pF 700mA N-Channel DFN-3L(0.6x1) MOSFETs ROHSALLPOWERMOSFETsBZX884C3V3
DFN1006-2LZener Diodesamsem
RB161QS-40
0402Schottky DiodesTECH PUBLIC
ABM8-272-T3
SMD3225-4P-40℃~+85℃ 10pF 12MHz 50Ω SMD crystal oscillator ±30ppm ±30ppm SMD3225-4P Crystals ROHSAbraconCrystals
README
README.mdrp24-dcc-decoder
DIY DCC decoder for model railroad locomotives in an E24 form factor suitable for N scale/gauge locomotives
Features
- 8x MOSFET-switched functions
- 5x GPIO pins (3.3V input/output)
- Up to 0.75A motor current
- E24 form factor (approx 20mm x 9mm)
- i2s audio speaker output
- 12V nominal rail voltage (16V max)
USB Programmer/E24 Tester
- USB-C port for easy programming and loading sound files
- Onboard LEDs for all aux outputs for simple decoder testing
- Breakout header for most E24 pins, including speaker, motor, rectified rail power, Vcc, plus all five E24 GPIO pins (Aux 3, 4, 10, 11, 12)
- Programming track input header allows for stationary decoder testing and CV programming
RP24 Decoder Pinout
| E24 Pin | Function | GPIO Pin |
|---|---|---|
| 1 | Speaker- | USB D- |
| 2 | Speaker+ | USB D+ |
| 3 | GND | GND |
| 4-5 | Motor- | N/A |
| 6-7 | Motor+ | N/A |
| 8 | Cap+ | GPIO20 |
| 9 | Lamp Front | GPIO6 (MOSFET) |
| 10 | Lamp Rear | GPIO7 (MOSFET) |
| 11 | AUX1 | GPIO8 (MOSFET) |
| 12 | AUX2 | GPIO5 (MOSFET) |
| 13 | AUX8 | GPIO4 (MOSFET) |
| 14 | AUX7 | GPIO3 (MOSFET) |
| 15 | AUX6 | GPIO9 (MOSFET) |
| 16 | AUX5 | GPIO2 (MOSFET) |
| 17 | U+ | DC Rail Voltage |
| 18 | Vcc | 3.3V |
| 19 | AUX10 | GPIO10 |
| 20 | AUX4 | GPIO13 |
| 21 | AUX3 | GPIO14 |
| 22 | GND | GND |
| 23 | AUX11 | GPIO0 |
| 24 | AUX12 | GPIO1 |
| N/A | Motor Driver A | GPIO25 |
| N/A | Motor Driver B | GPIO26 |
| N/A | Back EMF A | GPIO28 |
| N/A | Back EMF B | GPIO29 |
| N/A | DCC signal Left Rail | GPIO21 |
| N/A | DCC signal Right Rail | GPIO27 |
| N/A | RailCom Out | GPIO11 |
| N/A | Status LED | GPIO19 |
| N/A | i2s DIN | GPIO22 |
| N/A | i2s BCLK | GPIO23 |
| N/A | i2s LRCLK | GPIO24 |
| N/A | Charge external keepalive capacitor (PWM at very low duty cycle only) | GPIO20 |
E24 Receiver/Wire Breakout Board
Receiver Board Solder Pads
| E24 Pin | Function | Label |
|---|---|---|
| 1 | Speaker- | SPK |
| 2 | Speaker+ | SPK |
| 3 | GND | G |
| 4-5 | Motor- | - MOTOR + |
| 6-7 | Motor+ | - MOTOR + |
| 8 | External Capacitor+ | C |
| 9 | Lamp Front | F LAMP R |
| 10 | Lamp Rear | F LAMP R |
| 11 | AUX1 | 1 |
| 12 | AUX2 | 2 |
| 17 | DC Rail Voltage | RV |
| 18 | Microcontroller Voltage Output | Vcc |
| 19 | AUX10 | 10 |
| 20 | AUX4 | 4 |
| 21 | AUX3 | 3 |
| 22 | GND | G |
| 23 | AUX11 | 11 |
| 24 | AUX12 | 12 |
Inspired by the rp2040-decoder project by gab-k: https://github.com/gab-k/RP2040-Decoder
Reference:
E24
- RCD-124 (German): https://normen.railcommunity.de/RCD-124.pdf
- https://dccwiki.com/Locomotive_Interface/E24
RailCom
- NMRA S-9.3.2, Section 2
- Example RailCom transmitter circuit: CircuitJS
View this project on CADLAB.io.
Parts
543| Qty | Value | Footprint | References |
|---|---|---|---|
| 263 | NPTH | NPTH | KiKit_MB_10_1, KiKit_MB_10_2, KiKit_MB_10_3, KiKit_MB_10_4, KiKit_MB_10_5, KiKit_MB_10_10, KiKit_MB_10_11, KiKit_MB_10_12, KiKit_MB_10_13, KiKit_MB_10_14, KiKit_MB_10_15, KiKit_MB_10_16, KiKit_MB_10_17, KiKit_MB_10_18, KiKit_MB_10_19, KiKit_MB_10_20 +247 |
| 32 | 6.8K | rp2350-decoder:R_0201_0603Metric | R1, R1, R1, R1, R12, R12, R12, R12, R13, R13, R13, R13, R16, R16, R16, R16 +16 |
| 28 | 100nF | rp2350-decoder:C_0201_0603Metric | C1, C1, C1, C1, C12, C12, C12, C12, C13, C13, C13, C13, C14, C14, C14, C14 +12 |
| 24 | 1K | rp2350-decoder:R_0201_0603Metric | R2, R2, R2, R2, R15, R15, R15, R15, R17, R17, R17, R17, R19, R19, R19, R19 +8 |
| 20 | 4.7uF | rp2350-decoder:C_0201_0603Metric | C10, C10, C10, C10, C15, C15, C15, C15, C17, C17, C17, C17, C18, C18, C18, C18 +4 |
| 16 | DMN2991UDA-7B | rp2350-decoder:X2-DFN0806-6_L0.8-W0.6_X2-DFN0806-6 | Q5, Q5, Q5, Q5, Q6, Q6, Q6, Q6, Q7, Q7, Q7, Q7, Q8, Q8, Q8, Q8 |
| 16 | LMBR4020H3T5G | rp2350-decoder:U-DFN1608-2_L1.6-W0.8-RD | D1, D1, D1, D1, D2, D2, D2, D2, D3, D3, D3, D3, D4, D4, D4, D4 |
| 12 | 22R | rp2350-decoder:R_0201_0603Metric | R9, R9, R9, R9, R10, R10, R10, R10, R11, R11, R11, R11 |
| 8 | 10pF | rp2350-decoder:C_0201_0603Metric | C8, C8, C8, C8, C11, C11, C11, C11 |
| 8 | 2.2uF | rp2350-decoder:C_0402_1005Metric | C2, C2, C2, C2, C3, C3, C3, C3 |
| 8 | AP1606 | rp2350-decoder:Diodes_DFN1006-3 | Q1, Q1, Q1, Q1, Q2, Q2, Q2, Q2 |
| 8 | BZX884C3V3 | rp2350-decoder:DFN1006-2L-RD | D7, D7, D7, D7, D8, D8, D8, D8 |
| 8 | Fiducial | Fiducial | KiKit_FID_B_1, KiKit_FID_B_2, KiKit_FID_B_3, KiKit_FID_B_4, KiKit_FID_T_1, KiKit_FID_T_2, KiKit_FID_T_3, KiKit_FID_T_4 |
| 8 | NST847BPDP6T5G | rp2350-decoder:SOT-963 | Q3, Q3, Q3, Q3, Q4, Q4, Q4, Q4 |
| 8 | RB161QS-40 | rp2350-decoder:DIO-SMD_L1.0-W0.6-P0.65-RD | D5, D5, D5, D5, D6, D6, D6, D6 |
| 4 | 100uF | rp2350-decoder:C_1206_3216Metric | C6, C6, C6, C6 |
| 4 | 2.2K | rp2350-decoder:R_0201_0603Metric | R3, R3, R3, R3 |
| 4 | 22uF | rp2350-decoder:C_0603_1608Metric | C5, C5, C5, C5 |
| 4 | 3.3uH | rp2350-decoder:L_pol_2016 | L2, L2, L2, L2 |
| 4 | 33R | rp2350-decoder:R_0201_0603Metric | R14, R14, R14, R14 |
| 4 | 4.7uH | rp2350-decoder:IND-SMD_L2.5-W2.0-VLS252012CX-150M | L1, L1, L1, L1 |
| 4 | 47uF | rp2350-decoder:C_1206_3216Metric | C16, C16, C16, C16 |
| 4 | 5052702412 | rp2350-decoder:CONN-SMD_5052702412 | J3, J3, J3, J3 |
| 4 | ABM8-272-T3 | rp2350-decoder:Crystal_SMD_3225-4Pin_3.2x2.5mm | Y1, Y1, Y1, Y1 |
| 4 | AP63203WU | rp2350-decoder:TSOT-26_L2.9-W1.6-P0.95-LS2.8-BL | U2, U2, U2, U2 |
| 4 | BOOT | rp2350-decoder:SW-SMD_4P-L2.6-W1.6-P0.75-LS3.0 | SW1, SW1, SW1, SW1 |
| 4 | Blue LED | rp2350-decoder:LED_0402_1005Metric | D9, D9, D9, D9 |
| 4 | MAX98357AEWL+T | rp2350-decoder:WLP-9_L1.4-W1.3-P0.40-R3-C3-BR | U5, U5, U5, U5 |
| 4 | MD9927 | rp2350-decoder:WDFN-8_L2.0-W2.0-P0.50-BL-EP | U6, U6, U6, U6 |
| 4 | NCS2220AMUT1G | rp2350-decoder:DFN-8_L1.6-W1.6-P0.40-BL-EP | U1, U1, U1, U1 |
| 4 | RP2350A | rp2350-decoder:QFN-60_L7.0-W7.0-P0.40-TL-EP3.4 | U4, U4, U4, U4 |
| 4 | SWCLK | rp2350-decoder:Pogo Pad 0.8mm | J2, J2, J2, J2 |
| 4 | SWDIO | rp2350-decoder:Pogo Pad 0.8mm | J1, J1, J1, J1 |
| 4 | W25Q128JVPIQ | rp2350-decoder:WSON-8-1EP_6x5mm_P1.27mm_EP3.4x4.3mm | U3, U3, U3, U3 |
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Questions
How big is the Rp2350-decoder PCB?
It measures 70 × 70 mm and has 6 copper layers, 0.85 mm thick.
What parts does the Rp2350-decoder use?
543 parts, built around the RP2350A, AP63203WU, MAX98357AEWL+T and MD9927. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Rp2350-decoder KiCad files?
From the mikesmitty/rp24-dcc-decoder repository on GitHub, at the commit this page was made from: the board is hardware/rp2350-decoder/production/rp2350-decoder.kicad_pcb and its schematic hardware/e24-receiver-board/e24-receiver-board.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Rp2350-decoder design in my own project?
Its repository states no licence, so its author keeps all rights: ask mikesmitty before reusing the design.