Benefit of TMC2208 vs TMC2130

g_pwn

Can anyone tell me if there are any benefits what so ever of running a TMC2208 instead of a TMC2130?
I know TMC2130 communicates over SPI whereas the TMC2208 communicates over UART. I know that SPI requires more pins when compared to UART (I think this is correct).

Additionally there are talks of sensorless homing. Can anyone explain to me the differences between sensorless homing and auto leveling?

Thanks for the info!!

Samuel Pinches

Hi @g_pwn! I'm no expert, but my understanding is that the core of TMC 2100, 2130 and 2208 are all the same (same max motor current etc), and it is just the external communication options that differ. I've only tried the 2100 and 2130 in their dumb modes, and using the solder bridges - I have not tried the SPI communication yet on the 2130.

Auto levelling and sensorless homing are different things, I'll try to break it down.

In order for the printer to know the position of any of the axis, the printer has reference points that it moves to, where a sensor tells the printer that it has reached that point. These points are known as "home" points, and they do NOT have to be located at the zero coordinate, they can be set to any coordinate and simply tell the printer that it has reached that point.

At those home locations, there are several types of sensors that can be used, most  commonly mechanical switches that are hit, or optical interrupt sensors. However, there are other kinds of sensors that can be used, such as inductive sensors, or optical IR reflective sensors.

Sensorless homing is simply having no physical sensors mounted on the printer. Instead, the TMC2130 can be used as a sensor. Each stepper driver constantly monitors the motor current that it is delivering to the motor, and this current changes dramatically when the load increases on the motor. In this way, the stepper driver can detect when this current changes, and hence make an assumption that is has hit the end of travel on an axis. The stepper driver can then output a signal that can be wired into the motherboard as an endstop.

Normally, the endstops are mounted to each axis. However, for auto bed levelling, the accuracy needed means that it is favourable to mount the sensor on the printing head. For auto bed levelling, this sensor detects the home position at many points across the bed, to create a mesh or grid of correction values. The firmware then uses these deviation measurement values of the printing surface, and compensate for them by making small z-movements as it prints the first few layers.

The printer can be configured to use a separate sensor for Z-min homing, and for Auto bed levelling, or, you can configure the printer to use the auto bed levelling probe for both auto bed levelling , and as a z-min home sensor.

It is likely that you could use sensorless homing for auto bed levelling. As the z axis is dropped, when the nozzle hits the printing surface, the motor current should increase, and this should be able to be used as a signal for autobed levelling. The only disadvantage of this is the risk of damaging the printing surface or the nozzle. However, I can't say how well the sensorless homing will work on the z-axis, as there are two motors connected to that stepper driver in parallel.

g_pwn

10/10, excellent explanation!
Thanks for taking the time to answer!

I plan on setting up SPI once my A5 gets in. I've purchased Waterott's TMC2130's and from Dai's video he explained these already have it enabled (I guess he means no need to solder the jumper to the actual stepper).

From there I think I will try that auto leveling mod Steve posted on thingiverse.

My hope is to get a real smoothe prints!

Thanks again for taking the time to explain!

Samuel Pinches

No worries - good luck! 😉

netzmark

I just have found really interesting thread about the difference and benefit of 2208 vs 2130. I recommend to read carefully also the comments on the first page, they are same valuable as an initial description of the author.
http://forum.raise3d.com/viewtopic.php?t=6013