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OBD12

samnadol·OBD12·pcb/pcb.kicad_pcb

OBD12 PCB layout, top view — open source STM32 board by samnadol

About the OBD12 PCB

OBD12 is an open source STM32 PCB design by samnadol, published on GitHub. It is a 4-layer board measuring 41.8 × 39.9 mm, with 70 components from 31 distinct parts.

Its main chip is the STM32G431KBTx, from the STM32 family. Other key parts include the USBLC6-2SC6, FT230XS, SPX3819M5-L, LM66100DCK and TCAN337. By type, the board carries 28 capacitors, 20 resistors, 9 ICs, 5 LEDs, 3 diodes and 2 inductors.

It belongs with the power & battery and iot & wireless designs in this gallery.

From the project

PCB and Firmware for OBD12

OBD12 is a small OBD-II dongle. It plugs straight into a vehicle's J1962 diagnostic port and bridges the vehicle's high-speed CAN bus (ISO 15765-4) to Bluetooth Low Energy (BlueNRG-M2SP module) and to a USB-C serial port (FT230X). An STM32G431 runs the whole board.

The MCU is an STM32G431KBT6: Cortex-M4F, 128 KB flash, 32 KB RAM, running at 3.3 V.

Termination guidance - In a vehicle: leave R16, R17, and C18 unpopulated. The OBD port is a stub off an already-terminated bus (two 120 Ω ends = 60 Ω). Adding a third terminator loads the bus. - On the bench with only one other node: fit R16/R17…

Main components on the OBD12

STM32G431KBTxUSBLC6-2SC6FT230XSSPX3819M5-LLM66100DCKTCAN337LM2842XBLUENRG-M2SP

OBD12 bill of materials (BOM)

70 components, 31 distinct parts.

QtyPartRefs
1
STM32G431KBTx
U1
1
USBLC6-2SC6
U2
1
FT230XS
U3
1
SPX3819M5-L
U4
2
LM66100DCK
U5, U8
1
TCAN337
U6
1
LM2842X
U7
1
BLUENRG-M2SP
U9
1
830103622909
Y1
1
USB_C_Receptacle_USB2.0_16P
J2
1
RESET_BUTTON
SW1
1
LED_RED
DS1
4
LED_GREEN
DS2, DS3, DS4, DS5
1
PESD1CAN
D1
1
SMAJ24A
D2
1
SM5819PL-TP
D3
1
BLM18AG121SN1D
FB1
1
15uH
L1
5
1uF
C1, C9, C10, C16, C27
12
100nF
C2, C3, C4, C8, C11, C14, C15, C19 +4
Show 11 more
QtyPartRefs
8
10uF
C5, C12, C13, C17, C20, C23, C24, C28
2
12pF
C6, C7
1
4n7
C18
2
0R
R1, R2
5
10k
R3, R4, R13, R15, R18
4
1k02
R5, R6, R7, R20
2
5k1
R8, R9
4
60R
R10, R11, R16, R17
1
56k
R12
1
33k
R14
1
3k4
R19

OBD12 design files

The KiCad project lives in the samnadol/OBD12 repository on GitHub; these links point at the commit this page was built from.

OBD12: common questions

What microcontroller does the OBD12 use?

The OBD12 is built around the STM32G431KBTx, from the STM32 family.

How big is the OBD12 PCB?

The OBD12 measures 41.8 × 39.9 mm, has 4 copper layers and is 1.6062 mm thick.

How many components are on the OBD12?

70 components, from 31 distinct parts. The full bill of materials is listed on this page.

Where can I download the OBD12 design files?

From the samnadol/OBD12 repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.

Can I use the OBD12 design in my own project?

The repository has no license, so all rights stay with samnadol. Use it as a reference, and ask the author before reusing the design.

Can I test firmware for the OBD12 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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