SKR v1.3 - Sending 5v to signal on endstop?

Hi, I've made a voltage divider for my inductive proximity sensor that will be used with an SKR v1.3

Now I'm plugging it in directly into the 12v output of the board, spliced in with wires from the case and hotend cooling fans. When something is detected, the Signal line receives 5v. When nothing is detected, the line outputs 0v (zero volts).

I couldn't find a conclusive answer, but can the Signal line of Z-min (probe) handle 5v? (see another topic here) Or should I make it so that the voltage is even lower? Through some googling I found out that the analog voltage is 3,3v and digital voltage is 5v. But it didn't give me a conclusive number and I am not willing to take any risk since the SKR board is needed in a project that I need to finish soon!

I have also used another inductive sensor on my other 3D printer, but that was one with the type ending on 'BX'. This sensor has 'BY' at the end of it's type, this means this is sensor cannot use the same voltage divider that I used in my other machine with a diode.

Edited 2 time(s). Last edit at 11/11/2019 05:27PM by Ohmarinus.

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http://www.marinusdebeer.nl/

Z- Is pin P1.25

In table 5 of the LPC1768 datasheet [www.nxp.com]
If you search for "P1[25]" you will find it listed in table 5, Pin description . Note It has a little [1] next to it.
If you click on the little [1] It takes you to a key where it lists what the little [1] is
"[1] 5 V tolerant pad providing digital I/O functions with TTL levels and hysteresis. This pin is pulled up to a voltage level of 2.3 V to 2.6 V."

So yes the pin is a 5 volt tolerant.

Edited 1 time(s). Last edit at 11/11/2019 05:56PM by Dust.

Quote
Dust
Z- Is pin P1.25

In table 5 of the LPC1768 datasheet [www.nxp.com]
If you search for "P1[25]" you will find it listed in table 5, Pin description . Note It has a little [1] next to it.
If you click on the little [1] It takes you to a key where it lists what the little [1] is
"[1] 5 V tolerant pad providing digital I/O functions with TTL levels and hysteresis. This pin is pulled up to a voltage level of 2.3 V to 2.6 V."

So yes the pin is a 5 volt tolerant.

Thanks a lot for your answer. I didn't know that this was the way to look up this info.. Very interesting to see the data sheet!

What I am wondering now. I have everything running, but the probe doesn't activate the Signal correctly. The probe sends 5.18V to the Signal of Z-min. Everything else works in this machine, but the probe doesn't seem to work. Is 5.18V maybe the wrong voltage? Would anyone know what would be the correct voltage? Am I working against some pull-up or pull-down resistor that is in the SKR 1.3 and how do I know how to counter that?

When I short the Signal pin to Ground, it does register as TRIGGERED when doing a M119. But 5V doesn't trigger.

Edit:
Could this be a fix?? >> here

Quote
Pippy
Try putting a low value pull-down resistor from the sense pin (on the 3-pin end stop connector) to GND, try say 330R resistor. That should overcome the SKR 10k pull-up resistor and provide a clean 0V/+5V to the sense pin as your probe is triggered/non-triggered.

I have tried this 'solution', but now the Z-min pin is always triggered no matter what. So the 330R resistor from signal to ground is causing it to be triggered. Inverting endstop logic didn't make a difference sadly.

I hope there is another solution.. Maybe changing the z-min pin to a pin that is not influenced by a 10k pull-up resistor? Or can it be that the other pins I'm defining cannot handle 5v?

The only fix seems to be to desolder the 10k pullup resistor from the board?

Edited 5 time(s). Last edit at 11/12/2019 06:06PM by Ohmarinus.

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http://www.marinusdebeer.nl/

5.18v is ok.. the absolute max is 5.5v over that it will damage the pin.

The endstops are setup so that 0v is a the trigger.
Yes there is a 10K pull up restor (R11) on the board, designed so that the input voltage is high unless it is pulled low
Normally you would invert the endstop in software and disable the internal pullup, but the external pull up resistor means this doesnt work.

To summarize... your probe pulles the pin high and the pullup resitor pulles the pin high.

Options:
remove R11 from the pcb. see [www.youtube.com]
Electriacly invert the signal from the probe so that it goes to 0v when triggered. (needs aditional electronics to invert the signal)
use a different pin.. You have to check on the datasheat to see if it can or can't tollerate 5v. There arent many free pin on the skr1.3. so it comes down to what arent you using? Ie what stepper drivers do you have (does it use the uart pins etc) , do you have a E1? (ie are E1 step, directioan and enable pins avalabe?)

I dont like the idea of adding a 330k as a pull down. It creates a 10k+330R path from +3.3v to gnd.

Edited 4 time(s). Last edit at 11/13/2019 01:53AM by Dust.

Looking at the data sheet you linked earlier I have chosen to remap the pin for Z_MIN to the Servo Pin 2_00. In the data sheet I have seen that Pins 2_XX tolerate 5v input. Will try out soon. Going to connect everything again now.

Yes, it works! Finally without soldering anything. Sadly the bilinear bed leveling doesn't work well so I'll have to open a new post for that issue.

Edited 1 time(s). Last edit at 11/13/2019 12:54PM by Ohmarinus.

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http://www.marinusdebeer.nl/