Servo on a Duet 2 Wifi + Duex5

Fabio 0 · 30 Jun 2021, 09:40

Hello,
I am trying to use a little servo (SG90) on my Duet2 WiFi (RRF 3.2).
I have it connected to the PWM servo port 3 (PWM3) on the Duex - as it is the only unused heater I have.

Configuring it with

M950 S0 C"!duex.pwm3"

Then trying to make it move:

M280 P0 S100

Of course I tried all the other definitions for that header (exp.heater5, exp.18, !duex.e4heat), and different values for S, to no avail.

The servo works (I tried it connected to a PI). The wiring is signal on leftmost header pin, 5V center and GND on the rightmost.

Any ideas? THanks!

DIY-O-Sphere · 30 Jun 2021, 12:54

@fabio-0
~~https://forum.duet3d.com/topic/13016/rrf3-and-servo/9?_=1621456861076~~

~~You need a pull up resistor~~

Edit:
Incorrect link replaced
False statement deleted

Duex should already have high level on the servo connector

Fabio 0 · 30 Jun 2021, 13:59

@diy-o-sphere said in Servo on a Duet 2 Wifi + Duex5:

https://forum.duet3d.com/compose?tid=13016&title=RRF3 and servo

Using the "^" to enable the pullup resistor change nothing... I have no movement whatsoever.

Phaedrux · 1 Jul 2021, 02:16

Can you test with one of the other PWM capable pins on the Duex?

Can you send M950 S0 by itself and see what it reports back?

Do you also happen to be using a Bltouch?

Please share your config.g and the results of M122 and M98 P"config.g".

I also notice you're using fw 3.2, might want to update to 3.3.

https://github.com/Duet3D/RepRapFirmware/releases/download/3.3/Duet2and3Firmware-3.3.zip

Upload that zip file in the system tab in DWC.

Fabio 0 · 7 Jan 2021, 02:22

@phaedrux
I do not use a BlTouch.
I have updated to RRF 3.3, now I have connected the power of the servo to a buck converter for the 5v, with just the signal wire to the PWM pin of the header. The servo seems to move, but I cannot really control the range of movement. Not sure whether is a frequency issue.

The other PWM servo ports are unavailable as I am using the corresponding heater ports on the Duex5.
I have tried connecting the signal to the Fan- pin on one of the Fan PWM headers (still giving power through the buck converter) and defining it as a fan, but did not work.

M950 S0:

GPIO/servo port 0 pin (exp.heater5,exp.18) frequency 700Hz

m122.txt

config.g

EDIT: For some reason M42 works whereas M280 doesn't.
So, not sure whether I had a voltage issue on that particular PWM servo header... using the buck converter for the power seems to be working, though.
Thanks for the help.

Phaedrux · 1 Jul 2021, 02:22

@fabio-0 said in Servo on a Duet 2 Wifi + Duex5:

I do not use a BlTouch.

Reason I asked is because it uses a servo pin as well and that's usually servo 0, so you would have to use the next available servo index, 1. But not the case here.

@fabio-0 said in Servo on a Duet 2 Wifi + Duex5:

The other PWM servo ports are unavailable

Yes, I know, but temporarily testing the servo with one could tell us if it's the servo having the problem or the port.

@fabio-0 said in Servo on a Duet 2 Wifi + Duex5:

frequency 700Hz

You could experiment with different frequencies with M950 Q

Phaedrux · 1 Jul 2021, 02:23

@fabio-0 said in Servo on a Duet 2 Wifi + Duex5:

EDIT: For some reason M42 works whereas M280 doesn't.

Ah, well at least it's working. Still don't understand why though.

Fabio 0 · 7 Jan 2021, 02:26

@phaedrux
Gotcha.
by the way, I had to use exp.heater5, as !duex.pwm did not work.
I will play with the frequency, but now at 700 and with M42 it seems to finally respond as it should.
Also, theoretically it should work also on one of the PWM fan ports, but it doesn't.

Phaedrux · 1 Jul 2021, 02:26

@fabio-0 said in Servo on a Duet 2 Wifi + Duex5:

!duex.pwm did not work.

I wonder if removing the inversion (!) would have helped...

Fabio 0 · 1 Jul 2021, 02:27

@phaedrux
I had tried that, no dice.

dc42 · 1 Jul 2021, 09:41

@fabio-0 you definitely should not have the inversion when using a PWM connector on a Due X. But also you should not use a frequency as high as 700Hz.

This should work:

M950 S0 C"duex.pwm3"
M280 P0 S100

If you test the pin using M42, then M42 P0 S1 should make the control output go to +5V, and M42 P0 S0 should make it go to 0V.

DIY-O-Sphere · 1 Jul 2021, 23:25

@fabio-0 said in Servo on a Duet 2 Wifi + Duex5:

PWM fan ports

Here you definitely need a pullup resistor

Fabio 0 · 18 Jul 2021, 01:22

@dc42 said in Servo on a Duet 2 Wifi + Duex5:

280 P0 S100

Ok, sorry to come back to this post so late but I had other issues and I could not test further...

Now I managed to free other 3 heater ports on the Duex, so I got rid of the buck converter as I could connect all 4 servos to 4 pwm ports on the Duet.
Nothing works anymore.

I tried also this configuration but nothing... The only visible thing that happens when I invoke a M42 or M280 command is that the corresponding heater led lights up (and remains up). So, it could be that the ports do not deliver the 5v? Before, using only the signal pin they worked with an external 5v supply...