Home switch Debounce setup

Machine: Custom, external driver, nema 23

Board: C3d

Firmware: Smoothie

Just trying to figure out how to get the machine to jog off the home switches a set amount after homing so that they are not under load

Endstop Debounce count is still set to the factory 100 setting

I set the Alpha and Beta_Homing_Retract to 5mm. The machine homes, retracts off the endstop switches a bit, but then returns right back the same amount back onto the switches.

Am I missing a particular variable to get them to bounce off the endstops and STAY off them at a preset deistance?


alpha_fast_homing_rate_mm_s 100 # feedrates in mm/second
beta_fast_homing_rate_mm_s 100 # "
gamma_fast_homing_rate_mm_s 4 # "
alpha_slow_homing_rate_mm_s 5 # "
beta_slow_homing_rate_mm_s 5 # "
gamma_slow_homing_rate_mm_s 2 # "

alpha_homing_retract_mm 5 # distance in mm
beta_homing_retract_mm 5 # "
gamma_homing_retract_mm 0 # "

#endstop_debounce_count 100 # uncomment if you get noise on your endstops, default is 100

Debouncing is a software routine that filters noise from switches and isn’t directly related to retracting the carriage off the endstops. When mechanical switches transition from open to closed and vice versa it’s not a clean transition - if you look at it on a logic analyzer you’ll see the switch “bouncing” between the open and closed state for a very short period of time. Debouncing filters this phenomenon away. I’d only mess with this value if you’re having trouble with the machine inconsistently locating the X and/or Y endstops.

The homing retract values you set here affect how the homing cycle itself behaves. The machine will seek at the fast homing rate until it hits an endstop. It will then back off the endstop a certain amount (the “homing retract” value) to e.g. allow a switch to transition from on to off, then seek at the slow homing rate to more precisely determine where the endstop physically is. It will stop motion when the endstop is triggered and remain there in perpetuity until it’s commanded to move somewhere else. There is no option for the homing routine to move the head off the endstops after the homing cycle is complete. Fortunately, having the carriage rest on the endstops won’t damage them - all homing switches are designed to operate in either make or break manner and will work for their defined lifetime in either the closed or open position. Switch lifetime is typically measured in actuations, and for these small limit switches it’s in the hundreds of thousands.

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