picafe/bicolor-matrix-v2A 32x8 bicolor LED matrix module composed of 4 8x8 matrices based on the Holtek HT16K33A I2C LED driver. V1 paired it with a stacked adapter (RP2040 Zero + DS3231 module); V2 redesigns the matrix routing and puts an…
Adapter board r2 is an open-source printed circuit board by picafe, from the picafe/bicolor-matrix-v2 repository on GitHub. It is a 4-layer board of 68.4 × 33.3 mm with 54 parts on 50 nets, routed with 396 tracks and 160 vias.
It is built around the ESP32-C3-WROOM-02-H4, BMP580 and CH340X, with the SCD40-D-R2, AP2114HA-3.3TRG1 and LIS2DW12TR-MS among its other parts. Its parts include 18 capacitors, 12 resistors, 10 ICs, 4 connectors and 3 transistors. It belongs with the interfaces and adapters and lEDs and displays boards and the ESP32 and RISC-V boards of this library.
A 32x8 bicolor LED matrix module composed of 4 8x8 matrices based on the Holtek HT16K33A I2C LED driver. V1 paired it with a stacked adapter (RP2040 Zero + DS3231 module); V2 redesigns the matrix routing and puts an ESP32-C3, RTC, and environment sensors on a half-length adapter board behind the display.
V1 running as a clock
Inspired by the common 32x8 red LED matrix modules that use the MAX7219 IC, I wanted to make my own module but with more colours and functionality, while keeping the same asthetic.
I found these modules while browsing Aliexpress and thought they could look be a cool alternative, costing ~$15 for 10 modules. With the red and light green variant, you can have red, a light green, and orange all in one module. As far as I'm aware, there aren't RGB modules in a similar form factor, although you can take generic WS2818 8x8 matricies and 3D print a diffuser for them, although the footprint is much bigger. This project was also partially inspired by bitluni's LED magnet tiles which I found really cool.
Unlike the single colour matricies with 16 pins, these had 24. I found this Adafruit module and followed a similar schematic with the Holtek HT16K33A I2C LED driver.
For V2 I revisited the HT16K33A datasheet and realized any ROW/COL pin can map to any matrix row/column, thus routing got a lot simpler than matching Adafruit's pinout exactly.
| Board | Role |
|---|---|
| bicolour-matrix | 32×8 display: 4× HT16K33A + 4× 8×8 bicolour matrices |
| adapter-board-r2 | ESP32-C3-WROOM-02, CH340X USB-UART, YSN8900 RTC + CR2032, STCC4 (default CO₂; optional SCD41), SHT4x, BMP580, LIS2DW12 |
| button-board-r2 (optional / WIP) | OLED + light sensor + touch pads |
The adapter is half the length of the matrix board and mates with a pin header between the middle modules so that the stack stays stable without a case.
The button board is a separate interface that is connected to the adapter board with a 7-pin JST SH connector. This is meant to be customized and built by the user themselves, although I've included a sample design with an OLED, light sensor, and 2x touch pads you can start from. What you include and how you integrate it is up to you and how you want to design an enclosure.
Adapter board R2 (3D)
Matrix board R2 (3D)
Matrix board schematic
Adapter board R2 schematic
Matrix board PCB (four HT16K33A modules)
Adapter board R2 PCB
Prices are estimated from LCSC single-board quantities and AliExpress for the LED matrices.
bicolour-matrix)| Designator | Value | Footprint | Qty | LCSC | Unit cost (est.) | Line total (est.) |
|---|---|---|---|---|---|---|
| C1, C6 | 10 µF | 0805 | 2 | C440198 | $0.02 | $0.04 |
| C2, C3, C4, C5 | 100 nF | 0603 | 4 | C14663 | $0.01 | $0.04 |
| D1, D2, D3, D4 | 1N4148WS | SOD-323 | 4 | C2128 | $0.01 | $0.04 |
| J1, J2 | 1×04 pin header | Through hole | 2 | — | $0.05 | $0.10 |
| J3, J4 | JST SH 1×04 (Qwiic-style) | SMD | 2 | — | $0.15 | $0.30 |
| J5 | 1×02 socket | Through hole | 1 | — | $0.05 | $0.05 |
| LED1, LED2, LED3, LED4 | 8×8 bicolour matrix | Module | 4 | AliExpress | $2.00 | $8.00 |
| R3, R4, R5, R9, R10, R11, R13, R14, R15, R18, R19, R20 | 47 kΩ | 0603 | 12 | C25819 | $0.002 | $0.02 |
| U1, U2, U3, U4 | HT16K33A | SSOP-28 | 4 | C5444738 | $0.54 | $2.16 |
| Total (matrix, components only) | ~$10.75 |
adapter-board-r2)Default build uses the STCC4 for CO₂. An SCD41 (U7) can be fitted instead if R6/R8 are left open and the unpopulated R5/R7 0 Ω jumpers are fitted (routes the SHT4x onto the main I²C bus instead of the STCC4 compensation bus).
| Designator | Value | Footprint | Qty | LCSC | Unit cost (est.) | Line total (est.) |
|---|---|---|---|---|---|---|
| BT1 | CR2032 holder | SMD | 1 | C7498149 | $0.15 | $0.15 |
| C1 | 1 µF | 0603 | 1 | C15849 | $0.01 | $0.01 |
| C3, C5, C11, C12, C18 | 100 nF | 0603 | 5 | C14663 | $0.01 | $0.05 |
| C4, C8, C9, C10, C13, C14, C16, C17 | 100 nF | 0402 | 8 | C1525 | $0.005 | $0.04 |
| C15 | 10 µF | 0603 | 1 | C19702 | $0.02 | $0.02 |
| C2 | 10 µF | 0805 | 1 | C15850 | $0.03 | $0.03 |
| C6, C7 | 4.7 µF | 1206 | 2 | C29823 | $0.03 | $0.06 |
| D1 | B5817WS | SOD-323 | 1 | C7420329 | $0.05 | $0.05 |
| F1, F2 | 1.1 A fuse | 0805 | 2 | — | $0.05 | $0.10 |
| J1 | USB-C receptacle 14P | Through hole | 1 | C3151746 | $0.30 | $0.30 |
| J2 | JST SH 1×07 | SMD | 1 | — | $0.25 | $0.25 |
| J3 | 1×02 socket | Through hole | 1 | — | $0.05 | $0.05 |
| J4 | 1×04 socket | Through hole | 1 | — | $0.08 | $0.08 |
| Q1 | UMH3N | SOT-363 | 1 | — | $0.08 | $0.08 |
| Q2, Q3 | BSS138W | SOT-323 | 2 | C28646265 | $0.03 | $0.06 |
| R1, R2 | 10 kΩ | 0603 | 2 | C25804 | $0.002 | $0.004 |
| R3, R4 | 5.1 kΩ | 0603 | 2 | C23186 | $0.002 | $0.004 |
| R6, R8 | 0 Ω (STCC4 / SHT4x compensation) | 0402 | 2 | C17168 | $0.004 | $0.008 |
| R9, R10, R11, R12 | 4.7 kΩ | 0603 | 4 | C23162 | $0.002 | $0.008 |
| S1, S2 | Tactile button, 160 gf | PTS810 | 2 | C720477 | $0.10 | $0.20 |
| U1 | ESP32-C3-WROOM-02 | Module | 1 | C2934560 | $3.13 | $3.13 |
| U2 | USBLC6-2SC6 | SOT-23-6 | 1 | C7519 | $0.18 | $0.18 |
| U3 | CH340X | MSOP-10 | 1 | C3035748 | $0.67 | $0.67 |
| U4 | AP2114HA-3.3TRG1 | SOT-223 | 1 | C460314 | $0.25 | $0.25 |
| U5 | YSN8900AP3 | SMD3225-10P | 1 | C54780223 | $1.46 | $1.46 |
| U6 | SHT4x | DFN-4 | 1 | — | $1.20 | $1.20 |
| U8 | BMP580 | LGA-10 | 1 | C22391138 | $0.96 | $0.96 |
| U9 | LIS2DW12TR | LGA-12 | 1 | C189624 | $1.26 | $1.26 |
| U10 | STCC4 | LGA | 1 | C49191471 | $10.06 | $10.06 |
| Total (adapter, default build) | ~$20.73 |
Optional (not in default total): U7 SCD41 (~$18, C3659421) with R5/R7 fitted and R6/R8 open; leave U10 unpopulated.
Combined components (matrix + adapter, default): ~$31.48
(PCBs: ~$30 matrix + ~$12 adapter at JLCPCB)
| Qty | Value | Footprint | References |
|---|---|---|---|
| 8 | 100nF | PCM_JLCPCB:C_0402 | C4, C8, C9, C10, C13, C14, C16, C17 |
| 5 | 100nF | PCM_JLCPCB:C_0603 | C3, C5, C11, C12, C18 |
| 4 | 0Ω | PCM_JLCPCB:R_0402 | R5, R6, R7, R8 |
| 4 | 4.7kΩ | PCM_JLCPCB:R_0603 | R9, R10, R11, R12 |
| 2 | 1.1A | Fuse:Fuse_0805_2012Metric | F1, F2 |
| 2 | 10kΩ | PCM_JLCPCB:R_0603 | R1, R2 |
| 2 | 4.7uF | PCM_JLCPCB:C_1206 | C6, C7 |
| 2 | 5.1kΩ | PCM_JLCPCB:R_0603 | R3, R4 |
| 2 | BSS138W | Package_TO_SOT_SMD:SOT-323_SC-70 | Q2, Q3 |
| 2 | Tactile Button, 160gf | Button_Switch_SMD:SW_SPST_PTS810 | S1, S2 |
| 1 | 10uF | PCM_JLCPCB:C_0805 | C2 |
| 1 | 10uF | PCM_JLCPCB:C_0603 | C15 |
| 1 | 1uF | PCM_JLCPCB:C_0603 | C1 |
| 1 | AP2114HA-3.3TRG1 | Package_TO_SOT_SMD:SOT-223 | U4 |
| 1 | B5817WS | PCM_JLCPCB:D_SOD-323 | D1 |
| 1 | BMP580 | easyeda2kicad:LGA-10_L2.0-W2.0-P0.50-TL_BMP580 | U8 |
| 1 | Battery_Cell | easyeda2kicad:BAT-SMD_BS-CR2032-8 | BT1 |
| 1 | CH340X | Package_SO:MSOP-10_3x3mm_P0.5mm | U3 |
| 1 | Conn_01x02_Socket | Connector_PinSocket_2.54mm:PinSocket_1x02_P2.54mm_Vertical | J3 |
| 1 | Conn_01x04_Socket | Connector_PinSocket_2.54mm:PinSocket_1x04_P2.54mm_Vertical | J4 |
| 1 | Conn_01x07_Pin | Connector_JST:JST_SH_SM07B-SRSS-TB_1x07-1MP_P1.00mm_Horizontal | J2 |
| 1 | ESP32-C3-WROOM-02 | RF_Module:ESP32-C3-WROOM-02 | U1 |
| 1 | LIS2DW12TR | Package_LGA:LGA-12_2x2mm_P0.5mm | U9 |
| 1 | LOGO | LOGO | G*** |
| 1 | SCD40-D-R2 | Sensor:Sensirion_SCD4x-1EP_10.1x10.1mm_P1.25mm_EP4.8x4.8mm | U7 |
| 1 | SHT4x | Sensor_Humidity:Sensirion_DFN-4_1.5x1.5mm_P0.8mm_SHT4x_NoCentralPad | U6 |
| 1 | STCC4 | custom:STCC4 | U10 |
| 1 | UMH3N | Package_TO_SOT_SMD:SOT-363_SC-70-6 | Q1 |
| 1 | USBLC6-2SC6 | Package_TO_SOT_SMD:SOT-23-6 | U2 |
| 1 | USB_C_Receptacle_USB2.0_14P | easyeda2kicad:USB-C-TH_SHOUHAN_TYPE-C-14PLC-H10.0 | J1 |
| 1 | YSN8900AP3 | easyeda2kicad:OSC-SMD_10P-L3.2-W2.5-BL_RX8130CE | U5 |
picafe/bicolor-matrix-v2
A 32x8 bicolor LED matrix module composed of 4 8x8 matrices based on the Holtek HT16K33A I2C LED driver. V1 paired it with a stacked adapter (RP2040 Zero + DS3231 module); V2 redesigns the matrix routing and puts an…
picafe/bicolor-matrix-v2
A 32x8 bicolor LED matrix module composed of 4 8x8 matrices based on the Holtek HT16K33A I2C LED driver. V1 paired it with a stacked adapter (RP2040 Zero + DS3231 module); V2 redesigns the matrix routing and puts an…
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It measures 68.4 × 33.3 mm and has 4 copper layers, 1.6 mm thick.
54 parts, built around the ESP32-C3-WROOM-02-H4, BMP580, CH340X and SCD40-D-R2. 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.
From the picafe/bicolor-matrix-v2 repository on GitHub, at the commit this page was made from: the board is adapter-board-r2/adapter-board-r2.kicad_pcb and its schematic adapter-board-r2/adapter-board-r2.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Its repository states no licence, so its author keeps all rights: ask picafe before reusing the design.