esp-idf-can2http

CANbus to http bridge using esp32.
It's purpose is to be a bridge between a CAN-Bus and a HTTP-Server.

Software requirement

esp-idf v4.2-dev-2243 or later.
Use twai(Two-Wire Automotive Interface) driver instead of can driver.

Hardware requirements

SN65HVD23x CAN-BUS Transceiver

SN65HVD23x		ESP32	ESP32-S2	ESP32-C3
D(CTX)	--	GPIO21	GPIO17	GPIO9	(*1)
GND	--	GND	GND	GND
Vcc	--	3.3V	3.3V	3.3V
R(CRX)	--	GPIO22	GPIO18	GPIO10	(*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. But it may not work with other GPIOs.

(*2) N/C for SN65HVD232

Termination resistance
I used 150 ohms.

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)

NOTE
3V CAN Trasnceviers like VP230 are fully interoperable with 5V CAN trasnceviers like MCP2551.
Check here.

Installation for ESP32

git clone https://github.com/nopnop2002/esp-idf-can2http
cd esp-idf-can2http
idf.py set-target esp32
idf.py menuconfig
idf.py flash

Installation for ESP32-S2

git clone https://github.com/nopnop2002/esp-idf-can2http
cd esp-idf-can2http
idf.py set-target esp32s2
idf.py menuconfig
idf.py flash

Installation for ESP32-C3

git clone https://github.com/nopnop2002/esp-idf-can2http
cd esp-idf-can2http
idf.py set-target esp32c3
idf.py menuconfig
idf.py flash

Configuration

CAN Setting

WiFi Setting

You can use static IP.

You can connect using mDNS.

External HTTP Server Setting

The External HTTP Server receives CAN Bus received data.

Note
The Built-in HTTP Server receives CAN Bus transmittion data.

Definition from CANbus to HTTP

When CANbus data is received, it is sent by HTTP POST according to csv/can2http.csv.
The file can2http.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 HTTP-POST-Path of external HTTP server.
Each CAN-ID is allowed to appear only once in the whole file.

S,101,/post
E,101,/post
S,103,/post
E,103,/post

When a CAN frame with ID 0x101 is received, POST with the 'canid':257.
When a CAN frame with ID 0x103 is received, POST with the 'canid':259.

POST Parameter Example:
CAN-ID is a decimal number, not a hexadecimal number.

{"canid":257, "frame": "standard", "data": [16, 17, 18]}
{"canid":257, "frame": "extended", "data": [16, 17, 18]}
{"canid":259, "frame": "standard", "data": [16, 17, 18]}
{"canid":259, "frame": "extended", "data": [16, 17, 18]}

Definition from HTTP to CANbus

Not exist.
You can send any CAN-ID.

Send CANBus frame using curl

CAN-ID is specified in decimal number.

$ curl -X POST -H "Content-Type: application/json" -d '{"canid": 513, "frame": "standard", "data": [16, 17, 18]}' http://esp32-server.local:8000/api/twai/send
twai send successfully

$ curl -X POST -H "Content-Type: application/json" -d '{"canid": 513, "frame": "extended", "data": [16, 17, 18]}' http://esp32-server.local:8000/api/twai/send
twai send successfully

CANBus reception using UNO.

HTTP Server Using Tornado

sudo apt install python3-pip python3-setuptools
python -m pip install -U pip
python -m pip install -U wheel
python -m pip install tornado
cd tornado
python can.py

HTTP Server Using Flask

sudo apt install python3-pip python3-setuptools
python -m pip install -U pip
python -m pip install -U wheel
python -m pip install -U Werkzeug
python -m pip install flask
cd flask
python can.py

Brows received data Using Tornado/Flask

Open your browser and put the Server's IP in the address bar.

Visualize CAN-Frame

Using python

There is a lot of information on the internet about the Python + visualization library.

Using node.js

There is a lot of information on the internet about the node.js + real time visualization library.

Troubleshooting

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.

Reference

https://github.com/nopnop2002/esp-idf-can2mqtt

PyroMix62/esp-idf-can2http