Timer too close

Knowledge Base
1

Background

A “Timer too close” error occurs when the MCU attempts to schedule a timer for a target time that is in the past. It almost always occurs as a result of a message from the host requesting an action at a time that is now in the past.

It is important to understand that Klipper essentially knows which command was scheduled in the past, but not why it happened. For example, a message is delayed because the webcam is blocking the USB port: The message contains a command whose target time is now in the past, but the reason is beyond Klipper’s control.

Reasons

  • High system load of the host
  • High disk activity of the host
  • Swapping due to low free memory
  • Disk errors / dying SD card
  • Unstable voltage
  • Other hardware hogging the USB bus or other system resources
  • Running in a Virtual Machine
  • USB, UART or CANBUS wiring faults leading to extremely delayed messages
  • Electro-Magnetic Interference (EMI) affecting proper signal transmission or leading to high resend rates
  • Wrong Clock Reference used during building the board’s firmware (make menuconfig), confusing the timing between host and board
  • Bugs in slicers and/or macros can flood Klipper’s command queue with meaningless commands, e.g. dozens of fan speed changes per second.
  • Using unofficial “extra” modules or Klipper modifications outside the main line.

Potential solutions

  • Check for other resource-intensive processes running in parallel
  • Remove additional hardware, especially webcams and displays
  • Generally try to simplify your setup as much as possible
  • Check SD card for errors / replace SD card
  • Check for Under-voltage detected! errors / make sure to use a good and adequate power supply
  • Do not run data lines (USB, UART, CANBUS) close to or in parallel with high current lines such as heaters or steppers. Use high quality cables (shielded / ferrite core). Keep such cables as short as possible.
  • Ensure sufficient cooling of the host’s SBC to avoid CPU throttling due to overheating
  • Also see Advanced Trouble-Shooting / Graphing Klipper
  • Verify that the correct Clock Reference during building the board’s firmware is used. Mind that certain boards have various revisions / flavors that might require different clock settings
  • Identify and disable macros that continuously generate commands or data during printing, especially in response to frequently used commands.
  • Check the Gcode produced by the slicer for obvious, high frequency occurrences of certain commands, e.g. M106
  • Remove any Klipper modifications that are not part of the official Klipper repository
3 Likes