esp-idf-CANBus-Monitor

April 26, 2026 · View on GitHub

Monitor Canbus traffic.

USBCAN-V800

Background

Windows application for monitoring CANBus is published here.
This tool is designed to be used with this hardware.
bazaar487719_1

So, I made the hardware side with ESP32.

Application structure

+-------------+           +-------------+           +-------------+            +-------------+
| Windows     |           |   USB-TTL   |           |             |            | SN65HVD23x  |
| Application |<--(USB)-->|  Converter  |<--(TTL)-->|    ESP32    |<--(TWAI)-->|   CAN-BUS   |<--(CAN BUS)-->CAN Network
|             |           |             |           |             |            | Transceiver |
+-------------+           +-------------+           +-------------+            +-------------|

On the ESP32S2/S3, you can use USB instead of UART.

+-------------+                                     +-------------+            +-------------+
| Windows     |                                     |             |            | SN65HVD23x  |
| Application |<--------------(USB)---------------->| ESP32S2/S3  |<--(TWAI)-->|   CAN-BUS   |<--(CAN BUS)-->CAN Network
|             |                                     |             |            | Transceiver |
+-------------+                                     +-------------+            +-------------|

Software requirement

ESP-IDF V5.0 or later.
ESP-IDF V4.4 release branch reached EOL in July 2024.

Note for ESP-IDF V6
This option is required for ESP-IDF V6 because this project uses legacy drivers.

ESP-IDF V6 gives this warning, but it still works.

#warning "The legacy TWAI driver is deprecated, please use esp_twai.h"

Hardware requirements

Windows PC
Windows applications can be downloaded from here.
- V7.10
- V7.20
- V8.00
USB-TTL Converter or USB Mini Femail connector
ESP32 development board has USB.
This USB connects to Linux and is used for writing the firmware and displaying the LOG.
Need converter to connect with Windows PC.

Converter ESP32 ESP32-S2/S3 ESP32-C3/C6
RXD -- GPIO4 GPIO4 GPIO4 (*1)
TXD -- GPIO5 GPIO5 GPIO5 (*1)
GND -- GND GND GND

(*1) You can change using menuconfig.

ESP32-S2/S3 has a full-speed USB OTG peripheral with integrated transceivers and is compliant with the USB 1.1 specification.
GPIO19 and GPIO20 can be used as D- and D + of USB respectively.
On the ESP32S2/S3, you can use USB instead of UART.
I used this USB Mini femail Connector.
```
ESP32-S2/S3 BOARD          USB CONNECTOR
                           +--+
                           | || VCC
    [GPIO 19]    --------> | || D-
    [GPIO 20]    --------> | || D+
    [  GND  ]    --------> | || GND
                           +--+
```
SN65HVD23x CAN-BUS Transceiver
SN65HVD23x series has 230/231/232.
They differ in standby/sleep mode functionality.
Other features are the same.
Termination resistance
I used 150 ohms.

Converter		ESP32	ESP32-S2/S3	ESP32-C3/C6
RXD	--	GPIO4	GPIO4	GPIO4	(*1)
TXD	--	GPIO5	GPIO5	GPIO5	(*1)
GND	--	GND	GND	GND

Wireing

SN65HVD23x		ESP32	ESP32-S2/S3	ESP32-C3/C6
D(CTX)	--	GPIO21	GPIO0	GPIO0	(*1)
GND	--	GND	GND	GND
Vcc	--	3.3V	3.3V	3.3V
R(CRX)	--	GPIO22	GPIO1	GPIO1	(*1)
Vref	--	N/C	N/C	N/C
CANL	--				To CAN Bus
CANH	--				To CAN Bus
RS	--	GND	GND	GND	(*2)

(*1) You can change using menuconfig.

(*2) N/C for SN65HVD232

Test Circuit

   +-----------+   +-----------+   +-----------+ 
   | Atmega328 |   | Atmega328 |   |   ESP32   | 
   |           |   |           |   |           | 
   | Transmit  |   | Receive   |   | 21    22  | 
   +-----------+   +-----------+   +-----------+ 
     |       |       |       |       |       |   
   +-----------+   +-----------+     |       |   
   |           |   |           |     |       |   
   |  MCP2515  |   |  MCP2515  |     |       |   
   |           |   |           |     |       |   
   +-----------+   +-----------+     |       |   
     |       |       |       |       |       |   
   +-----------+   +-----------+   +-----------+ 
   |           |   |           |   | D       R | 
   |  MCP2551  |   |  MCP2551  |   |   VP230   | 
   | H      L  |   | H      L  |   | H       L | 
   +-----------+   +-----------+   +-----------+ 
     |       |       |       |       |       |   
     +--^^^--+       |       |       +--^^^--+
     |   R1  |       |       |       |   R2  |   
 |---+-------|-------+-------|-------+-------|---| BackBorn H
             |               |               |
             |               |               |
             |               |               |
 |-----------+---------------+---------------+---| BackBorn L

      +--^^^--+:Terminaror register
      R1:120 ohms
      R2:150 ohms(Not working at 120 ohms)

Installation

git clone https://github.com/nopnop2002/esp-idf-CANBus-Monitor
cd esp-idf-CANBus-Monitor
idf.py set-target {esp32/esp32s2/esp32s3/esp32c3/esp32c6}
idf.py menuconfig
idf.py flash