LinuxCNC configuration

Sample Configuration Files

Sample LinuxCNC configuration files can be found in the Remora/LinuxCNC/ConfigSamples directory. To copy all the samples into your LinuxCNC configuration for experimentation or customizing do the following on the rPi in a terminal window:

cp -a ~/linuxcnc/Remora/LinuxCNC/ConfigSamples/* ~/linuxcnc/configs

When you next start LinuxCNC you will find these items under the “My Configurations” node of the LinuxCNC Configuration Selector window.

Understanding the LinuxCNC configuration

The following sections give some further details regarding the purpose and function of the different portions of the configuration files.

Loading realtime components

Along with the standard realtime components (kinematics and motion module) the Remora component needs to be loaded. This will expose the pins and allow the Remora functions to be added to the servo thread.

# load the realtime components

    loadrt [KINS]KINEMATICS
    loadrt [EMCMOT]EMCMOT base_period_nsec=[EMCMOT]BASE_PERIOD servo_period_nsec=[EMCMOT]SERVO_PERIOD num_joints=[KINS]JOINTS

    # component selection is based on board/chip type. Uncomment based on your board
    # for STM32 based boards
    loadrt remora

    # for LPC17xx based boards
    #loadrt remora_lpc

Joint Control Type

Configuration the control mode for each individual joint. Options are Velocity or Position mode. Joints default to position mode.

loadrt remora ctrl_type=v,v,p

chip_type

Note: the chip_type option is depricated and replaced by seperate componsnets for each supported chip.
Option to configure for the chip type used on your controller board.
Options are LPC and STM
Default is LPC

loadrt remora chip_type=STM

SPI_clk_div

Option for setting the SPI clock divider
If you are unsure of this setting, you may omit it from your hal file.
Default is based on board type
Avaiable options are
128 = 3.125MHz on RPI3
64  = 6.250MHz on RPI3
32 =  12.5MHz on RPI3
16 = 25MHz on RPI3
Defaults are based on chip type.

loadrt remora chip_type=STM SPI_clk_div=32

PRU_base_freq

Option for setting the PRU frequency
This will be based on your specific chip type and the frequency it runs
Default is 40000 , but this needs to match your PRU_base_freq in firmware config
If you are unsure of your base thread frequency, it is displayed in serial terminal when the MCU is booted.

loadrt remora chip_type=STM SPI_clk_div=32 PRU_base_freq=40000

E-Stop Loop

To alert and stop LinuxCNC if SPI communication with the controller board cannot be estabilished, or if it is lost during operation, the Remora component is included as part of the LinuxCNC E-Stop loop. The HAL configuration is shown below.

# estop loopback, SPI comms enable and feedback

net user-enable-out     <= iocontrol.0.user-enable-out      => remora.SPI-enable
net user-request-enable <= iocontrol.0.user-request-enable  => remora.SPI-reset
net remora-status       <= remora.SPI-status                => iocontrol.0.emc-enable-in

Diagramatically this is shown in the following figure.

Adding functions to threads

The servo thread is used to communicate with the controller board and perform motion calculations. Functions are added in the order of execution. Firstly data is read from the controller board (remora.read), motion is then computed, stepper frequencies are calculated (remora.update-freq) and then the data is written to the controller board (remora.write).

# add the remora and motion functions to threads

    addf remora.read servo-thread
    addf motion-command-handler servo-thread
    addf motion-controller servo-thread
    addf remora.update-freq servo-thread
    addf remora.write servo-thread