Replace the A4988 by TMC2208 on an A20T: the order of the pins are reversed !! ??

[Nanounq]

Hello Geeetech World,

I want to put TMC2208 V2 to replace the original A4988.

But I see the TMC2208 have the pins order reversed from the original A4988s. If I give a name from 1 to 8 to each pin, starting from the potentiometer of the A4988, , the corresponding pins of the TMC2208 should be named 9 to 1, sarting from the potentiometer.
(for exmple, "Step" and "DIr" pins are on the side of the potentiometer on the A4988, and at the other side on the 2208).

I read in a post somewhere that the order of the pins has priority on the color of the two rows under the chip.

Which way should I put these TMC2208?

[gopher]

Hi!
Just look at my post
On my picture you will see everything!

[Nanounq]

Thank you Gopher.

I put the TMC2208 "upside down", same pin label same place. My printer is still working !

Now I have to settle the vref...

[gopher]

Great!
You should find equation of the vref, it depends on the resistance of one resistor on your driver and find the max I of your stepper motor.

Or just measure current vref on the a4988 and set vref on tmc2208 just a little bit less.

[Nanounq]

Trop tard pour mesurer les vref des A4988, je n'ai pas le courage de les remettre.

J'ai réglé les extrudeurs et les axes X et Y à .8 et l'axe Z à 1.1. Je vais surveiller la température des steppers et vérifier les e-steps.

Quant aux équations, voici un extrait d'un post sur Facebook (https://www.facebook.com/groups/3675586 ... 648107980/) :

I can't even remember how many times I have told people the formula for calculating the Vref for TMC2xxx stepper drivers.
Vref=( Irms x 2.5) / 1.77
Usually I'm in a rush, and something always seemed a bit off, and today it dawned on me what was off.
take this example

You want to set the current to 1 amp.


So, first you must convert that 1 amp to rms for the above formula
1/1.41=0.709 amps rms

Then
0.709 x 2.5 =1.7725
1.7725 / 1.77 = 1.00v vref
1.00 ?

That's the motor current we started with !!!!

Then I reread the exact same formula I've seen a hundred times....
Vref = (Irms * 2.5V) / 1.77A = Irms * 1.41 = Imax

DUH !
It says right there in plain english ( well, plain MATH )
Vref =Imax
In other words the vref voltage equals the motor current
so if you want to set the current to 1.0 Amp
the vref = 1.00
If the max current for your motor is 1.68 amps, the max vref you can set is.......... 1.68 !
So simple, I ( and others), have been making it difficult!

[Kashban]

Thank you Gopher.

I put the TMC2208 "upside down", same pin label same place. My printer is still working !

Now I have to settle the vref...

That worked for me too, splendid .

VRefs for my A20t are 1.019-1.025 V for the XYZ motors and 0.824V for the extruder motors.

With respect to the stepper motors my A20t is now silent enough (didn't put any dampeners in like on my Ender 3), just the hotend fan needs an upgrade to become much less noisy. Probably by printing a new fan duct and replace the original fan by something bigger and slower.

[Kashban]

Double post because of SQL connection issues with the forum, please ignore.