Midi-2-cv
About the Midi-2-cv PCB
Midi-2-cv is an open source STM32 PCB design by lennartquerter, published on GitHub under the CC-BY-NC-4.0 license. It is a 4-layer board measuring 50 × 110 mm, with 142 components from 88 distinct parts.
Its main chip is the STM32F411RETx, from the STM32 family. Other key parts include the TL074, LM13700, TL072, MCP4728 and LM1117DT-3.3. By type, the board carries 68 resistors, 29 capacitors, 10 ICs, 8 diodes, 4 transistors and 3 connectors.
It belongs with the audio designs in this gallery.
From the project
Lenimal Github for DIY for a Eurorack Synth
!! Please read the Issues at the end of the file before starting the build !!
This module is one of my first designs that include a MCU. I first designed the software around a STM32 Blackpill board, which I hooked up to some proto-type boards. The software was written in C and used the STM32 HAL library. I used the MCP4728 DAC to output the CV signals. Each DAC has 4 output channels and is driven by an I2C bus. The DAC 12-bit ranging from 0 to 2V. I use an OpAmp to amplify the signal to 0-8V.
Main components on the Midi-2-cv
Midi-2-cv bill of materials (BOM)
142 components, 88 distinct parts — part numbers from the project's BOM.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | TL074 6N135-L | DIP-8_W7.62mm | U1 |
| 1 | LM13700 TL074 | SOIC-14 | U2 |
| 1 | TL072 MCP4728 | MSOP-10_3x3mm_P0.5mm | U3 |
| 3 | TL074 | SOIC-14 | U4, U6, U7 |
| 2 | MCP4728 | MSOP-10_3x3mm_P0.5mm | U5, U10 |
| 1 | LM1117DT-3.3 | TO-252-3_TabPin2 | U8 |
| 1 | STM32F411RETx | LQFP-64_10x10mm_P0.5mm | U11 |
| 2 | MMBT3904 BC848 | SOT-23 | Q1, Q4 |
| 2 | MMBT3906 BC848 | SOT-23 | Q2, Q3 |
| 1 | 20MHZ | Crystal_SMD_HC49-SD_HandSoldering | Y1 |
| 1 | SD-50BV (DIN5) | SD-50BV (DIN5) | J1 |
| 1 | BOOT_RUN | PinHeader_1x03_P2.54mm_Vertical | J2 |
| 1 | Conn_01x04 | PinHeader_1x04_P2.54mm_Vertical | J3 |
| 1 | CV_OUT_1 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | CV_OUT_1 |
| 1 | CV_OUT_2 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | CV_OUT_2 |
| 1 | CV_OUT_3 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | CV_OUT_3 |
| 1 | CV_OUT_4 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | CV_OUT_4 |
| 1 | GATE_1 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | GATE_1 |
| 1 | GATE_3 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | GATE_2 |
| 1 | GATE_2 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | GATE_3 |
Show 68 more
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | GATE_4 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | GATE_4 |
| 1 | CONN_02X05_PWR_EURORACK Conn_02x05_PWR_Eurorack | IDC-Header_2x05_P2.54mm_Vertical | H1 |
| 1 | MOD_1 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | MOD_1 |
| 1 | MOD_2 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | MOD_2 |
| 1 | MOD_3 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | MOD_3 |
| 1 | MOD_4 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | MOD_4 |
| 1 | ON-OFF-ON | SW_default | SW1 |
| 1 | VEL_1 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | VEL_1 |
| 1 | VEL_2 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | VEL_2 |
| 1 | VEL_3 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | VEL_3 |
| 1 | VEL_4 | Jack_3.5mm_QingPu_WQP-PJ398SM_Vertical_CircularHoles | VEL_4 |
| 1 | 1N4148WS 1N4148 | D_SOD-123 | D1 |
| 2 | 1N4148WS 1N5819 | D_SOD-123 | D2, D3 |
| 1 | 1N4148WS LED | LED_0805_2012Metric_Pad1.15x1.40mm_HandSolder | D4 |
| 2 | 1N5819WS RED_OUT_20mA | LED_D3.0mm | D5, D6 |
| 2 | 1N4148 RED_OUT_20mA | LED_D3.0mm | D7, D8 |
| 1 | 120R | L_0805_2012Metric_Pad1.05x1.20mm_HandSolder | FB1 |
| 1 | 1NF 0.1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C1 |
| 1 | 470NF 0.1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C2 |
| 1 | 2.2UF 47uF | CP_Radial_D5.0mm_P2.50mm | C3 |
| 1 | 2.2UF 0.1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C4 |
| 1 | 47NF 47uF | CP_Radial_D5.0mm_P2.50mm | C5 |
| 1 | 33NF 0.1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C6 |
| 1 | 2.2NF 0.1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C7 |
| 1 | 10NF 0.1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C8 |
| 1 | 22NF 0.1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C9 |
| 2 | 47UF 0.1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C10, C14 |
| 4 | 100NF 0.1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C11, C12, C13, C17 |
| 2 | 100NF 10uF | CP_Radial_D4.0mm_P2.00mm | C15, C16 |
| 2 | 100NF 100nF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C18, C19 |
| 4 | 100nF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C20, C21, C23, C24 |
| 1 | 10uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C22 |
| 2 | 1uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C25, C26 |
| 2 | 10pF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C27, C28 |
| 1 | 2.2uF | C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C29 |
| 1 | 330K 220R | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R1 |
| 1 | 100K 10K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R2 |
| 1 | 100K 1K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R3 |
| 2 | 100K 10K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R4, R25 |
| 3 | 10K 30K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R5, R17, R26 |
| 5 | 10K 1K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R6, R12, R15, R21, R24 |
| 1 | 68K 10K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R7 |
| 1 | 180K 30K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R8 |
| 9 | 1K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R9, R36, R37, R48, R49, R54, R57, R60 +1 |
| 5 | 10K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R10, R55, R58, R61, R64 |
| 2 | 1K5 30K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R11, R23 |
| 1 | 2K2 10K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R13 |
| 1 | 33K 30K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R14 |
| 1 | 4K7 10K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R16 |
| 1 | 6K8 1K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R18 |
| 1 | 1K5 10K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R19 |
| 1 | 3K3 30K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R20 |
| 1 | 10K 10K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R22 |
| 2 | 100K 10R | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R27, R28 |
| 1 | 2K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R29 |
| 1 | 100K 470R | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R30 |
| 1 | 22K 470R | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R31 |
| 6 | 100K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R32, R41, R42, R45, R51, R53 |
| 1 | 10R 100K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R33 |
| 1 | 10R 22K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R34 |
| 3 | 22K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R35, R46, R47 |
| 1 | 120K 68K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R38 |
| 1 | 100K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R39 |
| 3 | 68K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R40, R50, R52 |
| 2 | 470R | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R43, R44 |
| 4 | 30K [0.1%] | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R56, R59, R62, R65 |
| 2 | 10K | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R66, R67 |
| 1 | 10R | R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R68 |
Midi-2-cv design files
The KiCad project lives in the lennartquerter/euro-rack-synth repository on GitHub; these links point at the commit this page was built from.
Midi-2-cv: common questions
What microcontroller does the Midi-2-cv use?
The Midi-2-cv is built around the STM32F411RETx, from the STM32 family.
How big is the Midi-2-cv PCB?
The Midi-2-cv measures 50 × 110 mm, has 4 copper layers and is 1.6 mm thick.
How many components are on the Midi-2-cv?
142 components, from 88 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 Midi-2-cv design files?
From the lennartquerter/euro-rack-synth 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 Midi-2-cv design in my own project?
It is published under CC-BY-NC-4.0, which limits how it may be reused; read the license before building on it.
Can I test firmware for the Midi-2-cv without the hardware?
Yes. HardLabs builds a simulation of the board from its netlist and BOM, so you can run and debug STM32 firmware against it before you order a PCB.
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