can2mqtt

can2mqtt connects a CAN-Bus to an MQTT broker and vice versa. You create pairs of CAN-Bus IDs and MQTT topics and choose a conversion mode between them.

Here you can see can2mqtt in action:

Installation

can2mqtt is written in Go and static linked binaries are available here. can2mqtt has no further dependencies. On a Raspberry for example it should be enough to run:

wget https://github.com/c3re/can2mqtt/releases/download/v2.2.1/can2mqtt-v2.2.1-linux-arm -O can2mqtt
chmod +x can2mqtt
./can2mqtt

Usage

The commandline parameters are the following:

./can2mqtt -f <can2mqtt.csv> -c <can-interface> -m <mqtt-connectstring> [-v]

Where can2mqtt.csv is the file for the configuration of can and mqtt pairs, can-interface is a socket-can interface and mqtt-connectstring is string that is accepted by the eclipse paho mqtt client. An additional -v flag can be passed to get verbose debug output. Example:

./can2mqtt -f /etc/can2mqtt.csv -c can0 -m tcp://127.0.0.1:1883

can2mqtt.csv

The file can2mqtt.csv has three columns. In the first column you need to specify the CAN-ID as a decimal number. In the second column you have to specify the convert-mode. You can find a list of available convert-modes below. In the last column you have to specify the MQTT-Topic. Each CAN-ID and each MQTT-Topic is allowed to appear only once in the whole file.

Example:

112,none,huette/all/a03/door/sensors/opened
113,2uint322ascii,huette/all/000/ccu/sensors/time
115,uint322ascii,huette/serverraum/000/filebitch/sensors/ftp_diskusage_percent
116,uint322ascii,huette/all/000/router/sensors/rx_bytes_s
117,uint322ascii,huette/all/000/router/sensors/tx_bytes_s
118,uint322ascii,huette/clubraum/000/ds18b20/sensors/temperatur
119,uint322ascii,huette/all/000/airmonitor/sensors/temp
120,uint322ascii,huette/all/000/airmonitor/sensors/hum
121,uint322ascii,huette/all/000/airmonitor/sensors/airq
122,uint322ascii,huette/all/000/airmonitor/sensors/pm2_5
123,uint322ascii,huette/all/000/airmonitor/sensors/pm10

Explanation for the 1st Line: For example our Doorstatus is published on the CAN-Bus every second with the CAN-ID 112 (decimal). can2mqtt will take everything that is published there and will push it through to mqtt-topic huette/all/a03/door/sensors/opened.

convert-modes

Here they are:

convertmode	description
none	does not convert anything. It just takes a bunch of bytes and hands it over to the other side. If you want to send strings, this will be your choice. If you have a mqtt payload that is longer than eight bytes, only the first eight bytes will be send via CAN.
bytecolor2colorcode	Converts an bytearray of 3 bytes to hexadecimal colorcode
pixelbin2ascii	This mode was designed to address colorized pixels. MQTT-wise you can insert a string like "<0-255> #RRGGBB" which will be converted to 4 byte on the CAN-BUS the first byte will be the number of the LED 0-255 and bytes 1, 2, 3 are the color of red, green and blue.
16bool2ascii	Interprets two bytes can-wise and publishes them as 16 boolean values to mqtt
uint
uint82ascii	one uint8 in the CAN-Frame to one uint8 as string in the mqtt payload
4uint82ascii	four uint8 in the CAN-Frame to four uint8 as string seperated by spaces in the mqtt payload.
8uint82ascii	eight uint8 in the CAN-Frame to eight uint8 as string seperated by spaces in the mqtt payload.
uint162ascii	one uint16 in the CAN-Frame to one uint16 as string in the mqtt payload
4uint162ascii	four uint16 in the CAN-Frame to four uint16 as string seperated by spaces in the mqtt payload.
uint322ascii	one uint32 in the CAN-Frame to one uint32 as string in the mqtt payload
2uint322ascii	two uint32 in the CAN-Frame to two uint32 as string seperated by spaces in the mqtt payload.
uint642ascii	one uint64 in the CAN-Frame to one uint64 as string in the mqtt payload
int
int82ascii	one int8 in the CAN-Frame to one int8 as string in the mqtt payload
4int82ascii	four int8 in the CAN-Frame to four int8 as string seperated by spaces in the mqtt payload.
8int82ascii	eight int8 in the CAN-Frame to eight int8 as string seperated by spaces in the mqtt payload.
int162ascii	one int16 in the CAN-Frame to one int16 as string in the mqtt payload
4int162ascii	four int16 in the CAN-Frame to four int16 as string seperated by spaces in the mqtt payload.
int322ascii	one int32 in the CAN-Frame to one int32 as string in the mqtt payload
2int322ascii	two int32 in the CAN-Frame to two int32 as string seperated by spaces in the mqtt payload.
int642ascii	one int64 in the CAN-Frame to one int64 as string in the mqtt payload

Unidirectional Mode

Normally can2mqtt works in bidirectional mode, that means all messages from the CAN-bus are send to mqtt and vice versa. If you wish you can run can2mqtt in a unidirectional mode to only send messages from can to mqtt or only mqtt to can. To do so you have to use the flag -d with one fo the following settings:

dirMode	effect
0	bidirectional mode, messages will be send from can to mqtt and vice versa
1	unidirectional mode, messages will only be send from CAN-Bus to mqtt broker
2	unidirectional mode, messages will only be send from mqtt broker to the CAN-Bus

Add a convert-Mode

If you want to add a convert-Mode think about a name. This is the name that you can later refer to when you want to use your convert-Mode in the can2mqtt.csv config-file. In this example the name of the new convert-Mode is "mymode". Next, add the new convert-Mode in the switch-case block in src/main.go. In the new case statement you refer to two functions. One is called when a MQTT-message is received and the other one when a CAN-frame is received. Change the contents of those functions to the behaviour that you seek for. Mockup code for MyModeToCan and MyModeToMqtt can be found in mymode.go.

Good luck & happy hacking ✌