Hello everyone, sorry for the delay.

As I see, it seems to be a limitation of the firmware (maybe my use case is too marginal).

To prevent this, I perform a custom macro that probe the bed, just to give me the mesh of the buildplate, in order to calibrate very precisely the flatness in X and Y axis.

Since the final aim is to get a "good layer thickness", my calibration is 2 times more sharp than the minimum layer thickness, so, even if the firmware give me a little drift, it is under my quality target.

I was measuring the accuracy and repeatability of the X and Y axes on my machine (DUET 6HC firmware 3.4.0 card) when I noticed some strange behaviour on the Z axis.
Each time Home X or Home Y is made, the Z position increases by a small increment which is equal to the deviation given by the height map.
For example, after doing Height Map, I have my XYZ origin = (0;0;0) for my tool.
I move the tool to the point (150;0;0) with the command G90 G0 X150.
The height map shows a flatness error of 0.2 mm in Z at point XY (150;0).
The tool therefore physically moves to the point (150;0;0.2) on the machine, which is actually at the co-ordinates (150;0;0) according to the height map.
I ask the machine for a Home X using the G28 X command.
Here is the gcode contained in the homex.g file:

G91; relative positioning
G1 H1 X-650 F1000 ; move quickly to X axis endstop and stop there (first pass)
G1 H2 X5 F1000 ; go back a few mm
G1 H1 X-650 F160 ; move slowly to X axis endstop once more (second pass)
G90 ; absolute positioning

The tool moves along X then comes into contact with the limit switch.
The tool coordinates then become (0;0;0.2): the machine has taken into account the Z deviation of the Height Map.

I repeat the same operation, this time asking the tool to move to the coordinates (70;0;0) using the G90 G0 X70 command.
The height map shows a very small Z deviation at this co-ordinate (0.002 mm observed).
I again request a home X with the G28 command.
After returning to the origin, the tool's co-ordinates are still (0;0;0.2), unchanged from the previous test.

This can be repeated for homing on the X and Y axes.

I tried to 'force' the Height Map to be taken into account when homing in the homex.g file, but the observations remain unchanged:

G91; relative positioning
G29 S1
G1 H1 X-650 F1000 ; move quickly to X axis endstop and stop there (first pass)
G1 H2 X5 F1000 ; go back a few mm
G1 H1 X-650 F160 ; move slowly to X axis endstop once more (second pass)
G90 ; absolute positioning

Is anyone experiencing the same phenomenon on their machine? Is this due to a firmware limitation?

Hello,

It seems to be solved. I just tried to connect each pin of the duet marked "used" (with dupont connectors), according to the wiring scheme , to my Raspeberry and they communicate. So I freed the GPIO 3.

Thank you,

Nicolas

Hello Chrishamm,

Thanks for your answer, but on the website of Duet (https://duet3d.dozuki.com/Wiki/SBC_Setup_for_Duet_3), it is said that :

"Duet 3 and SBC not communicating :

• Use of Pi cases that extend the GPIO pins or use the pins for external buttons or powering PWM fans will not work with the Duet."

That's why I didn't look in this way. But I see that you're a admin of the forum, so maybe you have more information for this use case. To your point of view, could it work with tour solution?

More, I just saw that, according to the pin mapping of the SPI bus, the GPIO 3 of the Raspberry Pi seems to be unused by the DUET 6HC. I am correct? could i "cut the wire" and use it for a power button on the Raspberry Pi? (see : https://duet3d.dozuki.com/Wiki/Duet_3_Mainboard_6HC_Wiring_Diagram)

Hello DIY-O-Sphere,

I agree that the shutdown could be set on every GPIO (according to Raspberry datasheet), however, I also need to restart the Raspberry after the shutdown, by a button, and not by unpluging/pluging the power (My Raspberry Pi will be set in a closed box, after electrical transformer, so no access for no one in this box).

Best regards,

Nicolas

Hello,

I have a Raspberry Pi 4B+ and a Duet 6HC. I want to connect them together and, now, I use the ribbon which connect The GPIO of the Raspberry to the GPIO of the DUET 6HC.
However, I need to shut down and (re)start the Rapsberry using au power button/switch.
Regarding to the data on the Rapsberry, it seems that only the GPIO 3 of the Raspberry is able to do that. But this GPIO 3 is also used by the ribbon of the DUET 6HC.

So, my questions are :

• Is there an other way to connect the DUET 6HC and the Raspberry Pi 4B+ without loosing any functionnality?
• If i will loose some functionnality, which are they?
• If it is necessary to use the ribbon, what is the exact use of GPIO 3 on the Raspberry 4B+?
• If the GPIO 2 & 3 on the Raspberry 4B+ are used for I2C communication, may I used the GPIO 0 & 1 on the Raspberry 4B+ which can also provide an I2C communication?

Best regards,

Nicolas

Hello,

Il would supply my Duet 6HC board with a 24V supply Meanwell RSP 320 24 (you can find the reference here :
https://fr.rs-online.com/web/p/alimentations-a-decoupage/7772850?cm_mmc=FR-PPC-DS3A--google--3_FR_FR_Alimentations+%C3%A0+d%C3%A9coupage_Mean+Well_Exact--Mean+Well+-+Alimentations+%C3%A0+d%C3%A9coupage+-+7772850--rsp+320+24&matchtype=e&kwd-331701590081&gclid=Cj0KCQiAoab_BRCxARIsANMx4S6dTEFXwZbo5FwMIiOzZ5nidRdFkJQRAhv299X_sB0VI1j2N8-rGrMaAjrrEALw_wcB&gclsrc=aw.ds
).
May tou tell my if it is necessary to add a ferrite on the wires between the supply and the Duet board?

Best regards,

Nicolas