235 lines
9.3 KiB
Markdown
235 lines
9.3 KiB
Markdown
# RPi microcontroller
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This document describes the process of running Klipper on a RPi and
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use the same RPi as secondary mcu.
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## Why use RPi as a secondary MCU?
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Often the MCUs dedicated to controlling 3D printers have a limited and
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pre-configured number of exposed pins to manage the main printing
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functions (thermal resistors, extruders, steppers ...). Using the RPi
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where Klipper is installed as a secondary MCU gives the possibility to
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directly use the GPIOs and the buses (i2c, spi) of the RPi inside
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klipper without using Octoprint plugins (if used) or external programs
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giving the ability to control everything within the print GCODE.
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**Warning**: If your platform is a _Beaglebone_ and you have correctly
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followed the installation steps, the linux mcu is already installed
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and configured for your system.
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## Install the rc script
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If you want to use the host as a secondary MCU the klipper_mcu process
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must run before the klippy process.
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After installing Klipper, install the script. run:
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```
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cd ~/klipper/
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sudo cp ./scripts/klipper-mcu.service /etc/systemd/system/
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sudo systemctl enable klipper-mcu.service
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```
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## Building the micro-controller code
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To compile the Klipper micro-controller code, start by configuring it
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for the "Linux process":
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```
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cd ~/klipper/
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make menuconfig
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```
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In the menu, set "Microcontroller Architecture" to "Linux process,"
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then save and exit.
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To build and install the new micro-controller code, run:
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```
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sudo service klipper stop
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make flash
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sudo service klipper start
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```
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If klippy.log reports a "Permission denied" error when attempting to
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connect to `/tmp/klipper_host_mcu` then you need to add your user to
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the tty group. The following command will add the "pi" user to the
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tty group:
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```
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sudo usermod -a -G tty pi
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```
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## Remaining configuration
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Complete the installation by configuring Klipper secondary MCU
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following the instructions in
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[RaspberryPi sample config](../config/sample-raspberry-pi.cfg) and
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[Multi MCU sample config](../config/sample-multi-mcu.cfg).
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## Optional: Enabling SPI
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Make sure the Linux SPI driver is enabled by running
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`sudo raspi-config` and enabling SPI under the "Interfacing options"
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menu.
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## Optional: Enabling I2C
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Make sure the Linux I2C driver is enabled by running `sudo raspi-config`
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and enabling I2C under the "Interfacing options" menu.
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If planning to use I2C for the MPU accelerometer, it is also required
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to set the baud rate to 400000 by: adding/uncommenting
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`dtparam=i2c_arm=on,i2c_arm_baudrate=400000` in `/boot/config.txt`
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(or `/boot/firmware/config.txt` in some distros).
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## Optional: Identify the correct gpiochip
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On Raspberry Pi and on many clones the pins exposed on the GPIO belong
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to the first gpiochip. They can therefore be used on klipper simply by
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referring them with the name `gpio0..n`. However, there are cases in
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which the exposed pins belong to gpiochips other than the first. For
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example in the case of some OrangePi models or if a Port Expander is
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used. In these cases it is useful to use the commands to access the
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_Linux GPIO character device_ to verify the configuration.
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To install the _Linux GPIO character device - binary_ on a debian
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based distro like octopi run:
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```
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sudo apt-get install gpiod
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```
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To check available gpiochip run:
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```
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gpiodetect
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```
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To check the pin number and the pin availability tun:
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```
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gpioinfo
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```
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The chosen pin can thus be used within the configuration as
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`gpiochip<n>/gpio<o>` where **n** is the chip number as seen by the
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`gpiodetect` command and **o** is the line number seen by the`
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gpioinfo` command.
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***Warning:*** only gpio marked as `unused` can be used. It is not
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possible for a _line_ to be used by multiple processes simultaneously.
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For example on a RPi 3B+ where klipper use the GPIO20 for a switch:
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```
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$ gpiodetect
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gpiochip0 [pinctrl-bcm2835] (54 lines)
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gpiochip1 [raspberrypi-exp-gpio] (8 lines)
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$ gpioinfo
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gpiochip0 - 54 lines:
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line 0: unnamed unused input active-high
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line 1: unnamed unused input active-high
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line 2: unnamed unused input active-high
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line 3: unnamed unused input active-high
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line 4: unnamed unused input active-high
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line 5: unnamed unused input active-high
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line 6: unnamed unused input active-high
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line 7: unnamed unused input active-high
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line 8: unnamed unused input active-high
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line 9: unnamed unused input active-high
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line 10: unnamed unused input active-high
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line 11: unnamed unused input active-high
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line 12: unnamed unused input active-high
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line 13: unnamed unused input active-high
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line 14: unnamed unused input active-high
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line 15: unnamed unused input active-high
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line 16: unnamed unused input active-high
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line 17: unnamed unused input active-high
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line 18: unnamed unused input active-high
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line 19: unnamed unused input active-high
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line 20: unnamed "klipper" output active-high [used]
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line 21: unnamed unused input active-high
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line 22: unnamed unused input active-high
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line 23: unnamed unused input active-high
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line 24: unnamed unused input active-high
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line 25: unnamed unused input active-high
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line 26: unnamed unused input active-high
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line 27: unnamed unused input active-high
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line 28: unnamed unused input active-high
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line 29: unnamed "led0" output active-high [used]
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line 30: unnamed unused input active-high
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line 31: unnamed unused input active-high
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line 32: unnamed unused input active-high
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line 33: unnamed unused input active-high
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line 34: unnamed unused input active-high
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line 35: unnamed unused input active-high
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line 36: unnamed unused input active-high
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line 37: unnamed unused input active-high
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line 38: unnamed unused input active-high
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line 39: unnamed unused input active-high
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line 40: unnamed unused input active-high
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line 41: unnamed unused input active-high
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line 42: unnamed unused input active-high
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line 43: unnamed unused input active-high
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line 44: unnamed unused input active-high
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line 45: unnamed unused input active-high
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line 46: unnamed unused input active-high
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line 47: unnamed unused input active-high
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line 48: unnamed unused input active-high
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line 49: unnamed unused input active-high
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line 50: unnamed unused input active-high
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line 51: unnamed unused input active-high
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line 52: unnamed unused input active-high
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line 53: unnamed unused input active-high
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gpiochip1 - 8 lines:
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line 0: unnamed unused input active-high
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line 1: unnamed unused input active-high
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line 2: unnamed "led1" output active-low [used]
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line 3: unnamed unused input active-high
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line 4: unnamed unused input active-high
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line 5: unnamed unused input active-high
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line 6: unnamed unused input active-high
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line 7: unnamed unused input active-high
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```
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## Optional: Hardware PWM
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Raspberry Pi's have two PWM channels (PWM0 and PWM1) which are exposed
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on the header or if not, can be routed to existing gpio pins. The
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Linux mcu daemon uses the pwmchip sysfs interface to control hardware
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pwm devices on Linux hosts. The pwm sysfs interface is not exposed by
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default on a Raspberry and can be activated by adding a line to
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`/boot/config.txt`:
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```
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# Enable pwmchip sysfs interface
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dtoverlay=pwm,pin=12,func=4
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```
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This example enables only PWM0 and routes it to gpio12. If both PWM
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channels need to be enabled you can use `pwm-2chan`.
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The overlay does not expose the pwm line on sysfs on boot and needs to
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be exported by echo'ing the number of the pwm channel to
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`/sys/class/pwm/pwmchip0/export`:
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```
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echo 0 > /sys/class/pwm/pwmchip0/export
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```
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This will create device `/sys/class/pwm/pwmchip0/pwm0` in the
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filesystem. The easiest way to do this is by adding this to
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`/etc/rc.local` before the `exit 0` line.
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With the sysfs in place, you can now use either the pwm channel(s) by
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adding the following piece of configuration to your `printer.cfg`:
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```
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[output_pin caselight]
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pin: host:pwmchip0/pwm0
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pwm: True
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hardware_pwm: True
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cycle_time: 0.000001
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```
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This will add hardware pwm control to gpio12 on the Pi (because the
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overlay was configured to route pwm0 to pin=12).
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PWM0 can be routed to gpio12 and gpio18, PWM1 can be routed to gpio13
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and gpio19:
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| PWM | gpio PIN | Func |
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| --- | -------- | ---- |
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| 0 | 12 | 4 |
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| 0 | 18 | 2 |
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| 1 | 13 | 4 |
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| 1 | 19 | 2 |
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