DuetWifi 1.0.1 and BL Touch Smart 3.0 - how to force 3.3V logic?

Nuffe

I have 1.0.1 version of DuetWifi, so I should try to force BL Touch to use 3.3V logic. But Smart 3.0 does not have traces to cut. See picture.

The documentation speaks about "Logic Voltage Free: 3.3V / 5V logic voltage free(default)", but if I take 5V from expansion board pin (according to setup guides=, how does that work? Or should I connect red wire to Z-probe 3.3V PIN?

A Former User

It defaults to open drain, so there is no positive voltage from the sensor, it only pulls the output to ground when active. When inactive it is up to the host to provide a pull up resistor to the correct voltage level.

Phaedrux

My understanding (though extremely limited) is that they have made the new probes not care anymore if it's 3.3 or 5v.

Nuffe

Ok, thank you both. So I'll do nothing for that.
If anyone is following this thread, seems like then I'll need some help with my BL Touch.

When I boot up my printer, BL Touch goes to 50% duty cycle red blinking led. I am able to reset that with S160, after that blue led lights up. But any command after that (eg. S120 or S10) causes red led to blink again.

I thought maybe there is some interference in the wires, but it behaves the same even if I separated the wires and twisted all BL touch wires together.

I will test this new BLTouch with my other printer having fully functional BLTouch setup (marlin).

Phaedrux

Perhaps give this a look: https://forum.duet3d.com/topic/10023/bltouch-v3-0-information-setup-and-o-scope-pictures

Nuffe

@phaedrux Thanks. I though BLTouch problem was on version 3.1 and I purchased intentionally V3.0 ... so due board version 1.0.1 I'll need to have pull up resistor if I understood correctly. Between white signal & 3.3V? Can that 3.3V be from Z-probe VCC?

Phaedrux

I'm unsure if that is correct. When it starts getting into voltages and resistors and all that it all gets a bit fuzzy for me.

My understanding though was that the BLTouch V3 shouldn't require anything additional to "Just work".

A Former User

open drain needs a pull up to give a stable idle state, end stops have pull ups but as far as i can see the zprobe inputs does not (but i seem to recall dc42 saying the mcu has weak internal pullups, that may or may not be sufficient. can just measure the voltage at the input pin when nothing is connected?)

Nuffe

@bearer said in DuetWifi 1.0.1 and BL Touch Smart 3.0 - how to force 3.3V logic?:

can just measure the voltage at the input pin when nothing is connected?

It is 2.95V. I do not know whether that is too low or not.

A Former User

thats close enough to say it has some sort of pull up resistor and should work just fine.

A Former User

Maybe this illustrates the logic levels well https://learn.sparkfun.com/tutorials/logic-levels/all#33-v-cmos-logic-levels

Nuffe

Back to square one then

Maybe it is faulty BL Touch. I'll test it with another printer tomorrow then.

Phaedrux

Very often problems with the BLTouch come down to the wiring. Either wired incorrectly, or an incomplete connection due to either damaged wire or crimp. A continuity tester comes in handy.

Second to that is a configuration problem.

This may help: https://duet3d.dozuki.com/Wiki/BLTouch_Troubleshooting

Nuffe

I test every cable when I build those, and did that multiple times afterwards too.

Configuration has been checked multiple times. I went through the troubleshooting section in the wiki pages.

But in any case I think those are correct because I am able to send s160 command to bltouch successfully to clear the error situation.

A Former User

if the input pin stays above the threshold for a high signal with the BL touch connected then the signaling should be okay i recon, if it for some reason gets pulled lower you need to add a stronger pull up resistor.

jinx

Any luck with this issue I'm having the same problem went from a v2.2 to 3 and nothing works

dc42

@jinx said in DuetWifi 1.0.1 and BL Touch Smart 3.0 - how to force 3.3V logic?:

Any luck with this issue I'm having the same problem went from a v2.2 to 3 and nothing works

Which Duet are you using, what firmware version, and what M558 command do you have in config,g?

jaurand

I am having this exact same problem. I started another thread a week ago as I tore down my old BLTouch and code and redid it. Now only S160 will clear errors. I am running latest firmware on Duet 2 Wifi. My next stop is to clear out all firmware and start from complete scratch

aidar

@Nuffe said in DuetWifi 1.0.1 and BL Touch Smart 3.0 - how to force 3.3V logic?:

I though BLTouch problem was on version 3.1 and I purchased intentionally V3.0

Hmm, i lately, about 2-3 weeks ago installed two of 3.1-s. One with Wifi, other with Maestro. Both works perfectly so far.

jinx

@dc42 so after some basic test I have come to the same conclusion that you have all made here, bad wiring!! the bl touch I got brand new out of the box white wire had a short. after putting in the older bl touch wring harness if you can call it that everything works fine. should have taken the time and tested every wire.

but thank you for putting up with me