LED-Wall Tile — CH32V003 Parallel-Bus WS2812B Controller (5×5)

A modular 5×5 WS2812B LED tile driven by a CH32V003 slave MCU.
Tiles share a simple 8-bit parallel bus + CLK + EN so a Raspberry Pi (or any MCU) can address many tiles and push pixel data quickly.

Highlights

• 25× WS2812B per tile (5 rows × 5 columns), daisy-chained on-board
• Parallel control bus: DATA0…DATA7, CLK, EN, optional RST
• MCU: WCH CH32V003F… (RISC-V, 3.3 V)
• Power: 5 V input for LEDs; onboard AMS1117-3.3 LDO for the MCU
• Connectors on four edges for tiling/rotation; pass-through for power & bus
• Status LED on a GPIO for quick diagnostics
• Designed with KiCad 9.0.3

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Repo structure

/wall/
  wall.kicad_pro
  wall.kicad_pcb
  wall.kicad_sch
  wall.kicad_prl
/media/
  wall_top_3d.jpeg
  wall_bottom_3d.jpeg
  wall_pcb.png
  wall_schematic.png
/firmware/        # (placeholder) CH32V003 code
/tools/           # (placeholder) host examples (Raspberry Pi)
README.md

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Images

• Top 3D: media/wall_top_3d.jpeg
• Bottom 3D: media/wall_bottom_3d.jpeg
• PCB layout: media/wall_pcb.png
• Schematic: media/wall_schematic.png

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Electrical overview

• LED matrix: 25 × WS2812B (5050). Data is routed serpentine per row.
• MCU: CH32V003F*P6 (labelled U1 in the schematic).
  • Parallel data bus on PC0…PC7
  • CLK and EN on PDx pins (see net labels in schematic)
  • PA1/PA2 used for the WS2812 data output to the first LED in the chain
  • RST net broken out (optional external reset)
• Power:
  • +5 V for LEDs
  • AMS1117-3.3 (U3) generates +3V3 for the MCU; C1/C2/C3 for decoupling
• Indicators: D26 + R4 connected to a GPIO (status / heartbeat)

⚠️ Current budget: Each WS2812B can draw up to 40 mA at full-white.
One tile worst-case ≈ 25 × 40 mA = 1.5 A @ 5 V (plus margin).
Size your power rails accordingly and avoid sustained full-white if thermals are tight.

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Connectors / Pinout

Each edge header is a 1×14 connector carrying power and the parallel bus.

Pin	Signal	Notes
1	DATA0	Parallel data bit 0 (MCU PC0)
2	DATA1	(PC1)
3	DATA2	(PC2)
4	DATA3	(PC3)
5	DATA4	(PC4)
6	DATA5	(PC5)
7	DATA6	(PC6)
8	DATA7	(PC7)
9	CLK	Rising edge latch (EXTI7_0 IRQ)
10	EN	Tile enable / latch (PDx)
11	GND	Ground
12	GND	Ground (second pin for current)
13	+5V	LED power
14	+5V	LED power (second pin for current)

Exact PDx assignments are labelled in the schematic nets; keep those in firmware defines so you can move them if the footprint changes.

• WS2812 data → PC7 / TIM2_CH2 (remap)
• Driven by TIM2 PWM + DMA

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Protocol

Each frame is transmitted as a sequence of bytes clocked on PD2 rising edge while the slave samples D0–D7.

Frame format:

SOF0 SOF1 ADDR CMD LEN PAY[LEN] CRC

• SOF0 = 0xA5
• SOF1 = 0x5A
• ADDR = 0–254 for unicast, 0xFF for broadcast
• CMD = command byte
• LEN = number of payload bytes
• PAY = payload
• CRC = Dallas/Maxim CRC8 (poly=0x31 reflected=0x8C, init=0x00) computed over ADDR..CMD..LEN..PAY

Commands

CMD	Name	LEN	Payload description
0x01	SET_ALL_RGB	3×N (75)	[R,G,B] triplets for all LEDs
0x02	SET_ONE_RGB	4	[index, R, G, B] (0–24 index)
0x03	FILL_RGB	3	[R, G, B] fill all LEDs
0x04	BOOT_TEST	0	Run built-in RGB test animation

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Firmware (CH32V003)

• Toolchain: WCH-RISC-V (MounRiver) or Open-source (e.g., riscv-none-elf-gcc + openocd for WCH-LinkE).
• Peripherals used:
  • GPIO for DATA[7:0], CLK, EN, LED
  • Timer or edge-detect to sample CLK while EN=1
  • Bit-banged or timer-driven WS2812 waveform output on PAx
• WS2812 timing: 800 kHz, 1.25 µs/bit. Use a timer and tight ISR/DMA-like loop to meet timing.

Build steps (outline):

1. Clone repo; open /kicad/wall.kicad_pro to view hardware.
2. Open /wall_code/ in your IDE; set your tile address in main.c.
3. Flash with WCH-LinkE via SWIO (PD1 on CH32V003). Provide a small 3-pin tag-connector or pogo-pads on your programmer.
4. Power at 5 V and verify the heartbeat LED.

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Example Host Frame

Set all 25 LEDs to red (255,0,0):

A5 5A 12 01 4B  FF 00 00 FF 00 00 ... (25 triplets) ... CRC

• 0xA5 0x5A = SOF
• 0x12 = target address
• 0x01 = SET_ALL_RGB
• 0x4B = 75 payload bytes
• Payload = 25× [FF,00,00]
• CRC = computed over ADDR..PAYLOAD

Raspberry Pi example (Python, pseudo-code)

2. Open host.py in your IDE.

Example Host Frame

Set all 25 LEDs to red (255,0,0):

A5 5A 12 01 4B  FF 00 00 FF 00 00 ... (25 triplets) ... CRC

• 0xA5 0x5A = SOF
• 0x12 = target address
• 0x01 = SET_ALL_RGB
• 0x4B = 75 payload bytes
• Payload = 25× [FF,00,00]
• CRC = computed over ADDR..PAYLOAD

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Manufacturing notes

• Layers: 2-layer, 1.6 mm FR-4, 1 oz Cu
• Min track/clearance: per your fab defaults (design uses moderate widths)
• Finish: HASL or ENIG
• Decoupling: place 0.1 µF near the MCU VDD and each LED power rail segment
• Mounting: corner holes + through-grid holes in the LED field (for diffusion/weight).

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Bring-up checklist

1. Power at 5 V and check +3V3 out of U3 (AMS1117-3.3).
2. Flash firmware; confirm status LED blinks.
3. With a logic analyzer, verify CLK edges and that DATA[7:0] are stable at each edge while EN=1.
4. Send a Fill command to a single address → tile lights uniformly.
5. Push a full 75-byte pixel buffer → verify 5×5 order matches your mapping.

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License

• Hardware: CC-BY-SA 4.0
• Firmware/Host code: MIT

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Credits

Designed by RMINGON.
KiCad project files: kicad/wall.* (created with KiCad 9.0.3).

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Bill-of-Materials (core)

Ref	Part	Notes
U1	CH32V003F…P6	3.3 V RISC-V MCU
U3	AMS1117-3.3	5 V → 3.3 V LDO
D1–D25	WS2812B	5 V addressable LEDs
D26, R4	Status LED + 5 Ω–1 kΩ	(value per brightness; schematic shows R4 5 Ω)
J1–J4	1×14 headers	Bus + Power
C1–C3	10 µF/0.1 µF mix	Regulator & MCU decoupling

Tweak values to match your inventory and regulator stability requirements (e.g., AMS1117 likes ≥10 µF on input/output).