Raspberry Pi 4 mmap

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10 Mar 2020 13:50 #159656 by COlger81
Replied by COlger81 on topic Raspberry Pi 4
No, i meant ethernet connection to 7i92m + 7i77.

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10 Mar 2020 13:52 #159657 by COlger81
Replied by COlger81 on topic Raspberry Pi 4
I was able to get it installed but latency on servo thread was 50,000,000 and GTK was not loading so i could not get gmoccapy to load.

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10 Mar 2020 13:56 #159658 by andypugh
Replied by andypugh on topic Raspberry Pi 4

I was able to get it installed but latency on servo thread was 50,000,000 and GTK was not loading so i could not get gmoccapy to load.


Which Raspbian image were you using?

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10 Mar 2020 14:08 - 10 Mar 2020 14:09 #159659 by PCW
Replied by PCW on topic Raspberry Pi 4

The limitation is at 96 I/O maximum it could be very low for some specific applications, maybe we could find a way to reach 128 or 256 user I/O using some new FPGA like ARTIX 35K or 100K, or creating 2x HM2 firmware in a single FPGA if there is enough cells. it could be very easy and with a double SPI communication (SPI0 and SPI1) 2x96 = 192 I/O


Current IDROM format limits I/O to 144 pins not 96, raising this to 1024 or so would really only mean increasing the IDROM size and changing a few constants. This is independent of FPGA type.
Last edit: 10 Mar 2020 14:09 by PCW.

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10 Mar 2020 15:34 #159662 by COlger81
Replied by COlger81 on topic Raspberry Pi 4
Buster with RT Preempt. Followed the gnipsel tutorial.

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10 Mar 2020 16:23 #159668 by PCW
Replied by PCW on topic Raspberry Pi 4
50 ms latency sounds like you are not actually running a real time kernel
what does:

uname -a

report?

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10 Mar 2020 17:04 #159672 by COlger81
Replied by COlger81 on topic Raspberry Pi 4
It reports the RT Preempt kernel...

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10 Mar 2020 17:09 #159673 by PCW
Replied by PCW on topic Raspberry Pi 4
Odd, I used the Gnipsel instructions and I get about 100 usec latency up to
maybe 200 if you run a browser/videos, How did you test latency?

I usually use
latency-histogram --nobase --sbinsize 1000

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10 Mar 2020 17:22 #159675 by COlger81
Replied by COlger81 on topic Raspberry Pi 4
I just run latency test. Base thread is good, around 50,000.

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10 Mar 2020 20:37 - 10 Mar 2020 20:39 #159696 by gtt38
Replied by gtt38 on topic Raspberry Pi 4

The limitation is at 96 I/O maximum it could be very low for some specific applications, maybe we could find a way to reach 128 or 256 user I/O using some new FPGA like ARTIX 35K or 100K, or creating 2x HM2 firmware in a single FPGA if there is enough cells. it could be very easy and with a double SPI communication (SPI0 and SPI1) 2x96 = 192 I/O


Current IDROM format limits I/O to 144 pins not 96, raising this to 1024 or so would really only mean increasing the IDROM size and changing a few constants. This is independent of FPGA type.

Thanks
The 3x20 has 144 I/O you're right. I have a XC6SLX25 with 189 user I/O, i should try a 144 I/O config and maybe try more...
I have few pb with IDROMconst, maybe you could help me. I added this line to this file with a random number, but it's not working, my board is unreconized :
constant BoardNameSLX25 : std_logic_vector(31 downto 0) := x"12384339";		-- Generic SLX25
github.com/youprint/Hostmot2SPI/blob/master/src/IDROMConst.vhd
i have to find the link into the linuxcnc source where the different boards are listed, maybe in rpspi.c
Last edit: 10 Mar 2020 20:39 by gtt38.

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