Changing an Isel FB2 to LinuxCNC?

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07 Feb 2022 19:58 - 07 Feb 2022 19:59 #234280 by andypugh

Since the 7c81 seems to come with matching firmware, this looks like the potentially easiest solution.

I wouldn't get too hung-up on the firmware, it's not generally too difficult to persuade PCW to make you one. 

Also, once you have the build environment set up to build the firmware, there is only one file to edit to build a custom one. Here is an example (that was made for me, hence the name) that contains both UART and smart-serial. The file declares what components are in the firmware, and which pins they use. [/quote]
Last edit: 07 Feb 2022 19:59 by andypugh.

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07 Feb 2022 20:33 #234287 by knipknap
I think a RS-232 to RS-485 adapter maybe would not work, because the (chain of) LS-173 uses full duplex (4 wire) RS-485, and I think RS-232 only does half duplex.

Sadly, that maybe also means that a Raspberry Hat would probably not work, because looking at the pinout of the Raspberry, it also has only two pins labels RX/TX, though I guess some IO pins may be re-purposed if the hat comes with a full duplex serial port driver.

So in summary, I still like the 7C81 option best, also because I like the form factor, I have several Raspberries lying around, and it is one of the few boards that are in stock in the EU...

Though I do like the simplicity of the HAL driver (.comp) for the serial port, this was easy to follow even for me, and I think I understand how HAL works now :-). My initial confusion came from thinking I would have to translate G commands into servo driver commands in the HAL driver, which I understand now is of course not needed.

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07 Feb 2022 21:07 #234289 by andypugh

I think a RS-232 to RS-485 adapter maybe would not work, because the (chain of) LS-173 uses full duplex (4 wire) RS-485, and I think RS-232 only does half duplex.


I am interpreting it as TX+ / TX- and RX+ / RX- differential pairs. I would expect a converter to do the TTL to differential conversion.

My initial confusion came from thinking I would have to translate G commands into servo driver commands in the HAL driver, which I understand now is of course not needed.


No, as you have probably realised, you just have to convert a velocity command that comes in on a HAL pin in to a formatted data packet. At least as a starting point. Handling the driver ID arbitration and setup will add incremental complexity, but that will come quite easily once the rest is there.

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07 Feb 2022 21:14 #234292 by knipknap

Ah, I see! That makes sense now. Then I'll try the serial option - that would seem to be both the easiest and cheapest approach.

Thanks for all the help!

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