Raspberry Pi based 4 axis controller

Quote
Mato
Hi,
I want to take attention to our new product. It is Control System PiDiCNC build on Raspberry Pi 2 and LinuxCNC.
For now we have done with first board for stepper motors based on FPGA. It can drive 4 steppers motors by Pololu DRV8825 directly from
this board or by external stepper driver STEP/DIR type. Max speed is 750kHz. Other features are 5 binary inputs,
3 binary outputs (each can be configured as BIN/PWM/RC servo), 1 relay output, 1 analog output (0-10V, 12bit) and 12 leds. All functions
are available from LinuxCNC by our HAL components. In this moment we made only few boards for testing but commercial production comming soon.
Next boards what we are working on are Analog Board for servo motors, encoders and additional Analog and Binary IO board.

Few slides and video with additional information:

[www.youtube.com]

Nice. Love the modular aspect of it. For a medium sized CNC setup, it looks good although from what I can see, it doesn't really meet my criteria:

1. Size: It's big-ish. My aim is to keep the size down so that it can be used as a motor controller in a small robot as well.
2. Completeness: There are no high current outputs. An external relay will be needed, particularly to drive the heaters for a 3D printer.
3. Simple: The FPGA is at a pin density where it becomes difficult to hand solder unless you know what you are doing.
4. Available: speaking of which, most people don't have FPGA programming tools available.
5. Price: 120 - 150 euro is more than a bit on the high side. I'm aiming for a board that costs less than US$50. At the moment, I think I can do it for about $40, but that will probably change. A big part of that is using a double layer board instead of a 4 layer board.

That said, I'm coming to the conclusion that an SPI based solution is probably the way to go, although I don't want to use a dedicated processor unless I have to.

PiDiCNC [www.youtube.com]

1. The size of the module is determined by the dimensions Raspberry PI and especially suitable box which is part of the system.
2. The board pidi_3805:
- 4 x outputs for motors (DRV8825), for larger currents are necessary external converters type DIR / STEP.
- 5 x electrically isolated inputs 0-24 Volt.
- 3 x electrically isolated - open collector 0-24 Volt / 0.2A
- 1 x relay output 230Volt / 5,0 A.
The board pidi_3809:
- 16 x electrically isolated inputs 0-24 Volt.
- 16 x electrically isolated outputs of 0-24 Volt / 2.0A.
3.4. All components are mounted on boards and are programmed. It is not necessary to add nothing. Only connect the power (24V), motors, inputs and outputs, configure and run.
If you need more motors, inputs or outputs, add another board.

Edited 3 time(s). Last edit at 11/10/2015 07:09AM by Mato.

If your not set on the Raspberry Pi I would suggest looking at the BeagleBone Black, it has the PRUs that can do realtime work and a community of support in the MachneKit project (forked from Linux CNC) and Replcape with Redeem. What your attempting has already been done on the BBB. On the other hand I'm all for experimenting but like DC42 said above you probably should look at one of the solutions with the large CPU small CPU model so that you can use the small CPU for the stepping/end stop monitoring and the big CPU for web interfaces etc.