Alternative to Raspberry PI

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13 Sep 2012 19:45 #24246 by Wyliest
The Raspberry Pi is a great board it has good GPIO and with a lot of the buses broken out this makes for easy to add things like ADC's and DAC's, small size, hardware LCD and touch screen controllers, and the price point doesn't hurt ether. But for some things it could be done better then using GPIO of the processor on the board: because LinuxCNC is not a true RTOS, real time performance is not 100%. Even if it was a true RTOS I think there are better ways to do some times. This is one of the virtues of a mesa card is a the FPGA can handle some of the really high speed and real time stuff like pulse generations, reading encoders, and so on. This is why you need a mesa card build right into the Raspberry PI. Maybe some thing like this.

www.armadeus.com/english/products-processor_boards-apf51.html

This has a ARM running at 800MHz with FPU, and more. It also has a 6A spartan FPGA just like a mesa card. This does not have the cost factor of the Raspberry PI, but size and GPIO and the fact of having a large FPGA it has it beat out.
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13 Sep 2012 22:59 #24251 by wizard69
How much in single lot quanities?

Beyond that LinuxCNC is an app running in conjunction with a realtime OS. Like all realtime OS's they are only useful if the processor is fast enough to keep up with the I/O involved.

They other problem here is FPGA Are great devices but you still need to program and debug them. In the case of step and direction controls they are a bit of an overkill as we can buy computer hardware capable of driving the machines without hardware support. It might be a different discussion if the hardware is cheap and development tools accessible and also cheap but experience tells me these boards aren't cheap.

Wyliest wrote:

The Raspberry Pi is a great board it has good GPIO and with a lot of the buses broken out this makes for easy to add things like ADC's and DAC's, small size, hardware LCD and touch screen controllers, and the price point doesn't hurt ether. But for some things it could be done better then using GPIO of the processor on the board: because LinuxCNC is not a true RTOS, real time performance is not 100%. Even if it was a true RTOS I think there are better ways to do some times. This is one of the virtues of a mesa card is a the FPGA can handle some of the really high speed and real time stuff like pulse generations, reading encoders, and so on. This is why you need a mesa card build right into the Raspberry PI. Maybe some thing like this.

www.armadeus.com/english/products-processor_boards-apf51.html

This has a ARM running at 800MHz with FPU, and more. It also has a 6A spartan FPGA just like a mesa card. This does not have the cost factor of the Raspberry PI, but size and GPIO and the fact of having a large FPGA it has it beat out.


Tell us the price. Further do they have a real time kernel running on the hardware. How about open FPGA code for I/O of servo control signals.
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14 Sep 2012 08:39 #24262 by ArcEye

Tell us the price.

Following the links to buy online gets 230 Euros for the APF51, whatever that is in real money.
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16 Sep 2012 09:15 - 16 Sep 2012 09:35 #24299 by Wyliest
Programming the FPGA is no problem, Meas Electronics provides the VHDL for the card and only some modification would be needed. As for kernel I am not sure. I am a embedded electronics guy so its not like I don't like that Idea of going to a small low power setup but I am not sure why not to just use a old computer and a mesa card in the end its about the same cost and much more functional. Although maybe some thing to also look at is some thing like the Olimex Linux computer. The micro is smaller and cheaper and has more GPIO.

www.olimex.com/Products/OLinuXino/iMX233/
Last Edit: 16 Sep 2012 09:35 by Wyliest.
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