Commons Board
About the Commons Board
Commons Board is an open source AVR/Arduino PCB design by Bad-Dog-Designs, published on GitHub. It is a 2-layer board measuring 229 × 96 mm, with 95 components from 41 distinct parts.
Its main chip is the ATMEGA328P-A, from the AVR/Arduino family. Other key parts include the TJA1050T/CM,118, MCP2515T-I/ST, MCP23017-E/SO and CD74HC4067SM. By type, the board carries 31 resistors, 16 capacitors, 12 diodes, 10 switches, 6 ICs and 4 connectors.
It belongs with the audio and displays & leds designs in this gallery.
From the project
Source code and KiCad Files for the build of an ESP32 S3 Based synthesizer. CAN bus is used extensively to collect all the pots and switch data and send to the ESP32 engine
Project overview: A custom polyphonic synthesizer built around an ESP32-S3 audio engine communicating with multiple ATmega328p control boards via CAN bus at 500kbps. All boards share synth_params.h as the single source of truth for CAN message definitions. Hardware boards:
ESP32-S3 — audio engine, MIDI input, I2S DAC output, CAN master Oscillator boards (ATmega328p, up to 4) — dual oscillator control per board, board ID set by hardware jumpers (both open = board 0) Commons board (ATmega328p) — filter, envelope, LFO, ring mod, play mode controls Routing board (ATmega328p) — modulation matrix…
Main components on the Commons Board
Commons Board bill of materials (BOM)
95 components, 41 distinct parts — part numbers from the project's BOM.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | TJA1050T/CM,118 TJA1050T_CM,118 | SOIC127P600X175-8N | IC1 |
| 1 | MCP2515T-I/ST MCP2515T-I_ST | SOP65P640X120-20N | IC2 |
| 2 | MCP23017-E/SO MCP23017-E_SO | SOIC127P1030X265-28N | IC3, IC4 |
| 1 | ATMEGA328P-A ATmega328P-A | TQFP-32_7x7mm_P0.8mm | U1 |
| 1 | CD74HC4067SM | SSOP-24_5.3x8.2mm_P0.65mm | U2 |
| 1 | 8MHZ 8Mhz | Crystal_HC49-4H_Vertical | Y1 |
| 1 | 16MHZ 16Mhz | Crystal_HC49-4H_Vertical | Y2 |
| 1 | ICP Header | PinSocket_2x03_P2.54mm_Vertical | J1 |
| 1 | Serial Mon | PinSocket_1x03_P2.54mm_Vertical | J2 |
| 1 | Output | JST_EH_S4B-EH_1x04_P2.50mm_Horizontal | J3 |
| 1 | Input | JST_EH_S4B-EH_1x04_P2.50mm_Horizontal | J4 |
| 1 | SR1712F-0108-20F0A-N9-N-027 Waveform_0 | SR1712F010820F0AN9N027 | S1 |
| 1 | SR1712F-0108-20F0A-N9-N-027 Range_0 | SR1712F010820F0AN9N027 | S2 |
| 1 | SR1712F-0108-20F0A-N9-N-027 Waveform_1 | SR1712F010820F0AN9N027 | S3 |
| 7 | TL2285OA | TL2285OA | S5, S6, S7, S8, S9, S10, S11 |
| 1 | RK09K1130AAU LFO1_Rate | RK09K1130AAU | VR1 |
| 1 | RK09K1130AAU LFO1_Depth | RK09K1130AAU | VR2 |
| 1 | RK09K1130AAU LFO2_Rate | RK09K1130AAU | VR3 |
| 1 | RK09K1130AAU LFO2_Depth | RK09K1130AAU | VR4 |
| 1 | RK09K1130AAU Mod_Level | RK09K1130AAU | VR5 |
Show 21 more
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | RK09K1130AAU Attack | RK09K1130AAU | VR6 |
| 1 | RK09K1130AAU Decay | RK09K1130AAU | VR7 |
| 1 | RK09K1130AAU Sustain | RK09K1130AAU | VR8 |
| 1 | RK09K1130AAU Release | RK09K1130AAU | VR9 |
| 1 | RK09K1130AAU Frequency | RK09K1130AAU | VR10 |
| 1 | RK09K1130AAU Resonance | RK09K1130AAU | VR11 |
| 1 | RK09K1130AAU Env_Track | RK09K1130AAU | VR12 |
| 1 | RK09K1130AAU Detune | RK09K1130AAU | VR13 |
| 12 | LED | LED_D3.0mm_FlatTop | D1, D2, D3, D4, D5, D6, D7, D8 +4 |
| 1 | 10R | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | FB1 |
| 4 | 22PF 22pf | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C1, C2, C6, C7 |
| 7 | 100NF 100nF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C3, C4, C5, C8, C9, C10, C11 |
| 2 | 1UF 1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C12, C13 |
| 1 | 4.7UF 4.7uF | CP_Radial_D4.0mm_P2.00mm | C14 |
| 1 | 100UF 100uF | CP_Radial_D4.0mm_P2.00mm | C15 |
| 1 | 10NF 1nF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C16 |
| 2 | 10K 10k | R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R1, R25 |
| 14 | 4K7 4k7 | R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R2, R3, R16, R17, R18, R19, R35, R36 +6 |
| 12 | 330R | R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R4, R5, R6, R7, R8, R9, R10, R11 +4 |
| 2 | 1k | R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R24, R53 |
| 1 | 120R | R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R28 |
Commons Board design files
The KiCad project lives in the Bad-Dog-Designs/ESP32-S3-Synthesizer repository on GitHub; these links point at the commit this page was built from.
Commons Board: common questions
What microcontroller does the Commons Board use?
The Commons Board is built around the ATMEGA328P-A, from the AVR/Arduino family.
How big is the Commons Board?
The Commons Board measures 229 × 96 mm, has 2 copper layers and is 1.6 mm thick.
How many components are on the Commons Board?
95 components, from 41 distinct parts, with part numbers taken from the project's own BOM. The full bill of materials is listed on this page.
Where can I download the Commons Board design files?
From the Bad-Dog-Designs/ESP32-S3-Synthesizer repository on GitHub, which has the KiCad layout, the schematic and the BOM; the links under Design files point to each one.
Can I use the Commons Board design in my own project?
The repository has no license, so all rights stay with Bad-Dog-Designs. Use it as a reference, and ask the author before reusing the design.
Can I test firmware for the Commons Board without the hardware?
Yes. HardLabs builds a simulation of the board from its netlist and BOM, so you can run and debug AVR/Arduino firmware against it before you order a PCB.
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