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UMO (1.5.7 PCB) & Marlin Endstop Interrupts?

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Posted (edited) · UMO (1.5.7 PCB) & Marlin Endstop Interrupts?

I'm running Marlin 1.1.8 on my UMO with its original 1.5.7 electronics and an Ulticontroller. I've been building a new version of Marlin 1.1.8 for my Bltouch sensor, which I'm about to hook-up and start testing. The Marlin source code says:

// Enable this feature if all enabled endstop pins are interrupt-capable.
// This will remove the need to poll the interrupt pins, saving many CPU cycles.

and the Antclabs Bltouch instructions say this feature is optional.

Does the 1.5.7 board have at least three interrupt-capable inputs? I only need three inputs because the Bltouch will use one input and provide a Z homing signal so that means I need only two more endstop interrupts for X and Y. Software limits works fine so I don't need MAX_PIN inputs as defined in the pins.ULTIMAKER.h file defaults here:

// Limit Switches
#define X_MIN_PIN          22
#define X_MAX_PIN          24
#define Y_MIN_PIN          26
#define Y_MAX_PIN          28
#define Z_MIN_PIN          30
#define Z_MAX_PIN          32

Even though it would be inconvenient to adapt the endstop switch connectors, they could perhaps be connected to pins 11, 12, 13 or maybe even pins 34 and 36, which are labeled "SERVOS" on the PCB silkscreen. I plan to connect my Bltouch control (servo) pin to pin 13 and it seems that pins 11, 12, and 13 are usually used for such things. Also from pins.ULTIMAKER.h:

// Servos
#define SERVO0_PIN         13 // untested


Does anyone here have experience with this? Did using interrupts work well (better than the default CPU polling)?


Once I get it up and running and tested, I'll fork the Marlin 1.1.8 source (or maybe I'll spin-up 1.1.9, which is the last 1.x.x Marlin, except for bug fixes) to my github account so others can give it a whirl.


BTW, this Bltouch V.2 mount looks pretty good to me. There's not all that much info on the Internet about this UMO mod or endstop interrupts.

Bltouch Mount

Same as above but with Google Translate to English







Edited by calinb

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Posted · UMO (1.5.7 PCB) & Marlin Endstop Interrupts?

What about using the x and y max pins? I never use mine and they seem completely redundant on the machine.


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Posted (edited) · UMO (1.5.7 PCB) & Marlin Endstop Interrupts?

I'd prefer to continue to use all the endstop switches, because they seem redundant until software doesn't behave as you might expect and then your stepper motors and drive mechanism crashes against the frame!🤮 It's the same with CNC machine tools. Endstop switches are safety switches.


I've already had a crash happen after configuring some Marlin features used with touch sensors. It is tricky and Marlin now has many features that are easy to mis-program and not catch the error until there's a crash. A full set of operating endstop switches protects the hardware.

Edited by calinb

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