New project, litehm2: a hostmot2 port to linsn rv901t

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22 Dec 2022 17:21 #260084 by sensille
While another thread explores the possibility to build an FPGA firmware + host driver from scratch, I went down a different road. I took the original Mesa code and ported it to the LiteX environment, starting with the linsn rv901t LED receiver board. This gives me the opportunity to have all modules from hostmot2 immediately available and access to the full ecosystem that already exists. Only minimal patches to LinuxCNC are needed.
The project is fully working and stable (so far) on my 6040. The Documentation is not finished yet, especially the part about customizing your configuration.

I included a bitstream that is ready to flash.

Any feedback is more than welcome.

github.com/sensille/litehm2
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26 Dec 2022 11:43 #260314 by tommylight
Thank you.
Did you check what step rates can it output?
Not that i am using it, but from what i read on this forum, that is the often asked question. :)
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26 Dec 2022 18:27 #260335 by sensille
To be honest I don't know that part of the hostmot2-stack that well, it's basically the same as for the mesa cards. The core runs with 100MHz, so I assume several MHz are easily possible. The limit could be dictated by the 74hc245 output drivers.
The stepper drivers i have require a minium pulse width and spacing of 1usec each, so the max rate they can handle is 500kHz, and the card very easily delivers that.
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26 Dec 2022 19:24 #260341 by tommylight
That is way more than what they are getting, i think. :)

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26 Dec 2022 22:05 #260352 by PCW
The Hostmot2 stepgen is limited by various pipeline delays to about 1/8 of its clock frequency. (so about 12.5 MHz at the normal 100 MHz clocklow)
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25 Apr 2023 08:43 #269828 by kubabuda
Hi, I see you rewrote Smartserial (SSLBP) master in C.
If I would translate it further into HAL comp, reading/writing from linux serial port (skipping FPGA), do you think this could work?
It would be way to use one or two remote Mesa cards over USB with UART adapter (+ RS 422 transceiver + RJ45 jack).
Obviously it would be limited by serial drivers and USB, so not real time. For human interfacing I/O like pendant, buttons this could be good enough.
Maybe has anyone did it already?

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27 Apr 2023 07:51 #270042 by sensille
I do not know much about Smartserial. I rewrote the LPB-code that runs on the mesa ethernet cards in C. Isn't there already code in the hostmod driver that talks LPB over serial?

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01 May 2023 02:42 #270372 by gulang123333
Hi,sensille,I am not an electrical engineer.
I saw the link github.com/sensille/litehm2 & github.com/q3k/chubby75/issues/85.
If I without any modifications to the RV901T, I will 24 output& 64 input ?
(Buffers
All I/O Buffers are powered by the 3.3V to 5.5V power supply.

Buffers U600 to U607 have a direction pin at F13. )
Can any one tell me where is F13?
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02 May 2023 05:51 #270448 by sensille
Regarding issue 85: To be honest I haven't thought about if it might be a problem to run the ports as inputs. I just assumed it works because the board is designed that way. It still works without problems.

24 Input/ 64 Output: Yes, although I'm not sure that really all I/O is available on the 2 large headers.

F13 is an FPGA pin. My firmware currently switches it to input, but that is easily changed.
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02 May 2023 15:46 #270488 by gulang123333
Thanks for your help,sensille。
About one and half moons ago, I got a emddebed board(rockchip rk3399)& make preempt_rt kernel (debian/ ubuntu),latency tset about 40-80 us。And then, I found your about rv901t github link .I found your plan better than collorlight.So, I bought a rv901t. I want to use your plan .Can you write in more detail about readme.txt? It's best to step by step.because now it's to hard for anyone except electrical engineer.

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