mirror of https://github.com/Desuuuu/klipper.git
94 lines
3.3 KiB
Markdown
94 lines
3.3 KiB
Markdown
# CANBUS
|
|
|
|
This document describes Klipper's CAN bus support.
|
|
|
|
## Device Hardware
|
|
|
|
Klipper currently only supports CAN on stm32 chips. In addition, the
|
|
micro-controller chip must support CAN and it must be on a board that
|
|
has a CAN transceiver.
|
|
|
|
To compile for CAN, run `make menuconfig` and select "CAN bus" as the
|
|
communication interface. Finally, compile the micro-controller code
|
|
and flash it to the target board.
|
|
|
|
## Host Hardware
|
|
|
|
In order to use a CAN bus, it is necessary to have a host adapter.
|
|
There are currently two common options:
|
|
|
|
1. Use a
|
|
[Waveshare Raspberry Pi CAN hat](https://www.waveshare.com/rs485-can-hat.htm)
|
|
or one of its many clones.
|
|
|
|
2. Use a USB CAN adapter (for example
|
|
[https://hacker-gadgets.com/product/cantact-usb-can-adapter/](https://hacker-gadgets.com/product/cantact-usb-can-adapter/)). There
|
|
are many different USB to CAN adapters available - when choosing
|
|
one, we recommend verifying it can run the
|
|
[candlelight firmware](https://github.com/candle-usb/candleLight_fw).
|
|
(Unfortunately, we've found some USB adapters run defective
|
|
firmware and are locked down, so verify before purchasing.)
|
|
|
|
It is also necessary to configure the host operating system to use the
|
|
adapter. This is typically done by creating a new file named
|
|
`/etc/network/interfaces.d/can0` with the following contents:
|
|
```
|
|
auto can0
|
|
iface can0 can static
|
|
bitrate 500000
|
|
up ifconfig $IFACE txqueuelen 128
|
|
```
|
|
|
|
Note that the "Raspberry Pi CAN hat" also requires
|
|
[changes to config.txt](https://www.waveshare.com/wiki/RS485_CAN_HAT).
|
|
|
|
## Terminating Resistors
|
|
|
|
A CAN bus should have two 120 ohm resistors between the CANH and CANL
|
|
wires. Ideally, one resistor located at each the end of the bus.
|
|
|
|
Note that some devices have a builtin 120 ohm resistor (for example,
|
|
the "Waveshare Raspberry Pi CAN hat" has a soldered on resistor that
|
|
can not be easily removed). Some devices do not include a resistor at
|
|
all. Other devices have a mechanism to select the resistor (typically
|
|
by connecting a "pin jumper"). Be sure to check the schematics of all
|
|
devices on the CAN bus to verify that there are two and only two 120
|
|
Ohm resistors on the bus.
|
|
|
|
To test that the resistors are correct, one can remove power to the
|
|
printer and use a multi-meter to check the resistance between the CANH
|
|
and CANL wires - it should report ~60 ohms on a correctly wired CAN
|
|
bus.
|
|
|
|
## Finding the canbus_uuid for new micro-controllers
|
|
|
|
Each micro-controller on the CAN bus is assigned a unique id based on
|
|
the factory chip identifier encoded into each micro-controller. To
|
|
find each micro-controller device id, make sure the hardware is
|
|
powered and wired correctly, and then run:
|
|
```
|
|
~/klippy-env/bin/python ~/klipper/scripts/canbus_query.py can0
|
|
```
|
|
|
|
If uninitialized CAN devices are detected the above command will
|
|
report lines like the following:
|
|
```
|
|
Found canbus_uuid=11aa22bb33cc
|
|
```
|
|
|
|
Each device will have a unique identifier. In the above example,
|
|
`11aa22bb33cc` is the micro-controller's "canbus_uuid".
|
|
|
|
Note that the `canbus_query.py` tool will only report uninitialized
|
|
devices - if Klipper (or a similar tool) configures the device then it
|
|
will no longer appear in the list.
|
|
|
|
## Configuring Klipper
|
|
|
|
Update the Klipper [mcu configuration](Config_Reference.md#mcu) to use
|
|
the CAN bus to communicate with the device - for example:
|
|
```
|
|
[mcu my_can_mcu]
|
|
canbus_uuid: 11aa22bb33cc
|
|
```
|