BLTouch on fan or heater pins on Duet Wifi

Googliola

I read the fantastic instructions on https://betrue3d.dk/bltouch-on-duet-wifi-configuratio-and-usage/#wiring
but I want to use just Duex5 for my 5 drivers & heaters for the extruders and cannot use the expansion header either. That's why I am looking for potential (PWM capable) alternative heater and fan pins on the Duet board. Here's where I'm stuck:

How would I setup the wiring (3 bltouch vs 2 board pins)?
What are the right pins for using a fan for PWM? P20 or P22 returns an error.
(I know I need to disable the heater pins first. No idea if/how to disable fan pins though..)

dc42

https://duet3d.dozuki.com/Wiki/Using_servos_and_controlling_unused_IO_pins covers how to disable fans to make their pins available.

Googliola

Thx @dc42 .
And how can I wire the bltouch to 2pins? Ground I get, but are the other pins polarity neutral?
Are there any other pins than the ones listed PWM capable?

dc42

You would need to connect the FAN- pin to the bltouch control wire and also connect a pull-up resistor between that wire and +5V. It will need to be a fan connector on the Duet, not on the DueX5. Don't connect to the V_FAN pin of the fan connector.

Are you really using all 8 heater outputs?

Googliola

@dc42 said in BLTouch on fan or heater pins on Duet Wifi:

Are you really using all 8 heater outputs?

No, I am not using all 8 heater outputs. But for the sake of a cleaner setup (all 5 extruders on duex), I opted to go this path.

The gcode I found here does not work as you cannot use M106 to control a servo (anymore)

Edit: I finally found a way to use BLTouch on a fan output.
Just to have it documented for others:
I am using Fan2 on Duet Wifi to control BLTouch. Follow the excellent instructions on https://betrue3d.dk/bltouch-on-duet-wifi-configuratio-and-usage

There are 2 differences in my setup:
In config.g replace
M307 H7 A-1 C-1 D-1 ;Disable the 7th Heater to free up PWM channel 5 on the Duex board.
with
M106 P2 I-1 ; Disable fan 2 for BLTouch PWM

In deployprobe.g use
M280 P22 I1 S10 ; use this when connected to fan 2

retractprobe.g use
M280 P22 I1 S90 ; use this when connected to fan 2

If you choose another fan, for example fan 0, change config.g such as
M106 P0 I-1 ; Disable fan 0 for BLTouch PWM

and in deploy and retract scripts
M280 P20 I1 S10 ; where Pn corresponds to PIN number, not fan number as outlined here

Here is a picture of my wiring:
IMPORTANT: connecting the PWM Fan2 wire to the V_FAN pin (marked with an X) will most likely fry your BLTouch!!!

0_1538310614231_63b74d40-51e7-48c7-ac80-ebef80b4e99b-image.png

For the 5V connection, I recommend using at least a 23 or even better a 25 connector for better reliability and to prevent wrong polarisation.

dc42

Do you have it working now?

Googliola

@dc42 Yes!
Struggling with tool-changing macros now... Don't seem to call any of them in 2.02RC2...

dc42

Did you home the printer first? Tool change macros are not called if axes are flagged as not homed.

FallenHorseman

Hi, I'm trying to copy your work into my project.
Unfortunately I've to deal with 8 Heaters: 4 Beds and 4 Extruders.
I'm having the 'new' version of BL Touch

I tried to use the FAN2 as it seems promissing.
The probe is doing it's self-test but doesn't react to any retract, deploy messages.
Even when I just try to send the M280 P22 I1 S10 ; M280 P22 I1 S90; manually.

As the Heater pins are working, I guess I missed something else...
Right now I don't have access to my scope, so I'd like to avoid any risky actions..
My first guess:
May it be possible that I have to put a pull-up resistor between 5V and the PWM of the FAN?

Note to all guys: Yeah 4k7Ohm Pullup to 5V is resolving that issues

Sorry for bothering you, next time I'll considering checking the Circuit before asking.
BTW: Thanks for the idea with the Fan PWM Googliola
Cheers,
Roland

dc42

@fallenhorseman said in BLTouch on fan or heater pins on Duet Wifi:

Hi, I'm trying to copy your work into my project.
Unfortunately I've to deal with 8 Heaters: 4 Beds and 4 Extruders.
I'm having the 'new' version of BL Touch

I tried to use the FAN2 as it seems promissing.
The probe is doing it's self-test but doesn't react to any retract, deploy messages.
Even when I just try to send the M280 P22 I1 S10 ; M280 P22 I1 S90; manually.

As the Heater pins are working, I guess I missed something else...
Right now I don't have access to my scope, so I'd like to avoid any risky actions..
My first guess:
May it be possible that I have to put a pull-up resistor between 5V and the PWM of the FAN?

Note to all guys: Yeah 4k7Ohm Pullup to 5V is resolving that issues

Sorry for bothering you, next time I'll considering checking the Circuit before asking.
BTW: Thanks for the idea with the Fan PWM Googliola
Cheers,
Roland

That's right, the fan outputs are open-drain so to use them as servo outputs you need a pullup resistor to +5V.

Googliola

@fallenhorseman Glad I could help.

Note to all guys: Yeah 4k7Ohm Pullup to 5V is resolving that issues

Funnily, I dont need a pullup between 5V and the PWM of the FAN, but I need one between GND and Z-Probe (as you can barely see in my picture . I use the 'old' version of BLTouch which is not 3.3V 'tolerant'. Am I missing something or is that a typo on your side?