CANbus to USB bridge using esp32.
The 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.
It's purpose is to be a bridge between a CAN-Bus and a USB OTG.
Unlike the standard serial port, the USB OTG port does not display initial output from the ROM bootloader.
esp-idf v4.4/v5.0.
This is because this version supports ESP32-S3.
-
ESP32-S2/S3 Development board
Because the ESP32-S2/S3 does support USB OTG. -
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. -
USB Connector
I used this:
ESP32-S2/S3 BOARD USB CONNECTOR
+--+
| || VCC
[GPIO 19] --------> | || D-
[GPIO 20] --------> | || D+
[ GND ] --------> | || GND
+--+
This connector is used with USB OTG.
| SN65HVD23x | ESP32-S2/S3 | ||
|---|---|---|---|
| D(CTX) | -- | GPIO17 | (*1) |
| GND | -- | GND | |
| Vcc | -- | 3.3V | |
| R(CRX) | -- | GPIO18 | (*1) |
| Vref | -- | N/C | |
| CANL | -- | To CAN Bus | |
| CANH | -- | To CAN Bus | |
| RS | -- | GND | (*2) |
(*1) You can change using menuconfig.
(*2) N/C for SN65HVD232
+-----------+ +-----------+ +-----------+
| Atmega328 | | Atmega328 | | ESP32-S2 |
| | | | | |
| Transmit | | Receive | | 17 18 |
+-----------+ +-----------+ +-----------+
| | | | | |
+-----------+ +-----------+ | |
| | | | | |
| 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)
NOTE
3V CAN Trasnceviers like VP230 are fully interoperable with 5V CAN trasnceviers like MCP2551.
Check here.
git clone https://github.com/nopnop2002/esp-idf-can2usb
cd esp-idf-can2usb
idf.py set-target {esp32s2/esp32s3}
idf.py menuconfig
idf.py flash
When CANbus data is received, it is sent by USB OTG according to csv/can2usb.csv.
The file can2usb.csv has three columns.
In the first column you need to specify the CAN Frame type.
The CAN frame type is either S(Standard frame) or E(Extended frame).
In the second column you have to specify the CAN-ID as a hexdecimal number.
In the last column you have to specify the Frame Name. This project does not use this column.
S,101,Water Temperature
E,101,Water Pressure
S,103,Gas Temperature
E,103,Gas Pressure
When you connect the USB cable to the USB port on your Windows machine and build the firmware, a new COM port will appear.
Open a new COM port in the terminal software.
I used TeraTerm.
When you connect the USB cable to the USB port on your Linux machine and build the firmware, a new /dev/tty device will appear.
Open a new tty device in the terminal software.
Most occasions, the device is /dev/ttyACM0.
I used screen.
You can use read.py script. python read.py
After writing the firmware, the ESP32 can get power from the USB OTG.
ESP32-S2/S3 BOARD USB CONNECTOR
+--+
[ VIN ] --------> | || VCC
[GPIO 19] --------> | || D-
[GPIO 20] --------> | || D+
[ GND ] --------> | || GND
+--+
There is a module of SN65HVD230 like this.
There is a 120 ohms terminating resistor on the left side.
I have removed the terminating resistor.
And I used a external resistance of 150 ohms.
A transmission fail is fixed.
If the transmission fails, these are the possible causes.
- There is no receiving app on CanBus.
- The speed does not match the receiver.
- There is no terminating resistor on the CanBus.
- There are three terminating resistors on the CanBus.
- The resistance value of the terminating resistor is incorrect.
- Stub length in CAN bus is too long. See here.