:: anybody saw the FPGA kickstarter ? ::

anybody saw this? and is trying something printee on it lol?

[www.kickstarter.com]

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Its nice I think I want one. But I will wait till they get all the bugs worked out.

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I had a play with an Altera dev kit a while back. An FPGA would make a really nice stepper controller, able to handle precise, coordinated motion profiles.

Only thing is, FPGAs are not cheap. For the price of the Spartan 6 FPGA you can get a Cortex-M4 running at 150MHz with change, so if you were going to create a dedicated solution with an FPGA, it seems to be more useful and probably as effective to create one using an MCU instead.

I noticed that Trinamic do a 3-axis motion controller chip [www.trinamic.com], could be interesting.

In general though, for the type of control required for printing, a fast 32 bit MCU seems to be sufficient.

i guess if things get any more complicated ... most likely whoever that is going to implement it will be closed sourcing it ...

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__my mixed bag blog || aka --> [http] || ___ so 3D printing is everywhere ... dont worry, hospitals can now 3Dprint body parts, they will charge you $1million excluding surgical fees ... you will die paying your debts. thats their aim ___ if every patent expires tomorrow, everybody will surely get a 3dprinter and make EVERYTHING ! ____ there is a "DIY-DTG" t shirt printing forum, you can mod an EPSON printer to PRINT like a pro. ___ CNCzone? overly commercialized it seems ___ my country? they will be taxing you for every cm of road you use and track you to your grave using GPS and its government authorized, now they will fire all the traffic wardens instead.___ EEVBLOG? there is only 1 way to do things --> take it apart like a pro

It might be worth mentioning Smoothstepper, which is an FPGA based CNC controller, and you are right it is not open source.

One drawback to FPGA development is the lack of open source tools for them, they tend to be proprietary and manufacturer specific. I think there has been more interest in FPGA recently, maybe due to Bitcoin miners.

I draw comfort from Linux, it is a complex piece of software, and competes with billion dollar corps like Microsoft. In the case of Android, it beats Microsoft's offering and possibly Apple as well.

Cypress have some chips which combine ARM cpu with programmable logic blocks, also Microchip have some PICs with simple configurable logic cells. If these trends continue, we might see more CPUs with ability for programmable peripherals, and get the best of both worlds.

Just when I thought I was up to date.... I don't get it : )

I have done some FPGA projects and sometimes it would have been easier with an MCU. FPGA are great for doing things in true parallel
There are open source FPGA stepper motor projects. Open Cores has open FPGA projects to suite most tastes.
Here is a link to a stepper motor project: [opencores.org]
I see that they say it is a beginner project

Edited 1 time(s). Last edit at 04/09/2013 11:35AM by SouthT.

I cant beleive people budgeting this project lol.. similar things have been out there for a while O.o hes not offering -anything- new.

As for the FPGA, im actually working on something like this already.. basically for fun purposes only. if someone does feel like teaming up then let me know! but dont expect much from this.. i dont expect FPGA to be able to swap the MCU for this purpose - its too complex.

I agree.
I have an STM32F103 (Arm Cortex-M3) based board I built for 3D printing and it's pretty fast already. STM do a Cortex M4 that would do everything my one is, even faster and with time spare for other things. The chips in common use in the popular 3D printer PCBs these days already do much of the work my cortex chip is doing, I only needed a fast chip because I'm directly controlling the coil polarities and doing microcontroller controlled PWM. Oh.. and I modified it to do delta calculations too.

The cortex M4 is plenty fast enough...

Graham.

Open loop PWM is only accurate when the motor is moving slowly. You need to measure the coil currents like chopper drivers do to get accurate microstepping during motion when the generated BEMF and inductive BEMF have a large effect.

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nophead Wrote:
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> Open loop PWM is only accurate when the motor is
> moving slowly. You need to measure the coil
> currents like chopper drivers do to get accurate
> microstepping during motion when the generated
> BEMF and inductive BEMF have a large effect.

Good point but I noticed that at least one of the currently used firmwares only does partial intermediary position calculations and assumes that the motors will follow correct paths between calculated xyz coordinates. On a Delta this could give some odd build grain. Slicer configurations can generally compensate for lead/lag by creating gcode requests for slower motion in the build portions with high acceleration/deceleration forces. I expect a good test would be to compare parallel 45 deg lines drawn in opposite directions at fixed distances apart with the same mechanics but different hardware, i.e. chopper drivers vs open loop PWM drivers.