A blast from the past for PCW

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10 May 2024 03:46 #300283 by PCW
Replied by PCW on topic A blast from the past for PCW
No, there is no SPI interface on the 8I20
There is access to the serial interface on the header

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10 May 2024 04:03 #300286 by blazini36
SPI interface coming off that PIC and some *special* firmware, I think it'd be a different beast....

.....just sayin lol

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10 May 2024 12:12 #300312 by PCW
Replied by PCW on topic A blast from the past for PCW
SPI is not a great off board interface to line operated power devices...

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10 May 2024 13:07 #300320 by tommylight

SPI is not a great off board interface to line operated power devices...

+1

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10 May 2024 23:47 #300360 by blazini36

SPI is not a great off board interface to line operated power devices...
 

What's the concern using SPI in a board to board configuration on something like an 8i20 that's powered off a DC bus of the user's making? the 8i20 isn't really scared of isolators so I'll get the obvious out of the way and I assume that motor driver doesn't spray too much EMI all over the transmission lines cuz it looks like a PIC sits right on top of it.

It's a hypothetical question anyway since it doesn't actually exist but what problem couldn't be overcome with a little consideration on either side?

Kind of a moot point but the STMBL has an SPI header on it, for whatever that's worth.
 

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11 May 2024 00:08 - 11 May 2024 00:14 #300362 by PCW
Replied by PCW on topic A blast from the past for PCW
On card with a ground plane SPI is fine. Between cards in a motor drive
with volts of ground bumping  and clock signals that are susceptible to 10 ns
spikes would likely require isolation. Isolation is a bit fussy for SPI because it needs
3 or 4 pins and skew is important (a good reason to use serial instead)
Its certainly possible but unless you had a good reason to do it, its probably not
worth the trouble.

 
Last edit: 11 May 2024 00:14 by PCW.

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11 May 2024 00:41 #300364 by blazini36

On card with a ground plane SPI is fine. Between cards in a motor drive
with volts of ground bumping  and clock signals that are susceptible to 10 ns
spikes would likely require isolation. Isolation is a bit fussy for SPI because it needs
3 or 4 pins and skew is important (a good reason to use serial instead)
Its certainly possible but unless you had a good reason to do it, its probably not
worth the trouble.


 

EtherCAT!!!!

Now that I think about it SPI wouldn't do any good anyway. I doubt you could have that PIC do the things it's currently doing and be the EtherCAT application processor as well. ESC would likely have to connect to a dedicated MCU on that PCB then yeah maybe that MCU could just interface the 8i20's PIC over serial.

I haven't put a ton of thought into it, I just saw my 8i20 and said "wow that's a cool idea". Does the current serial protocol/ firmware etc facilitate the purpose of the Unicorn board that may or may not have turned it into a velocity mode drive?

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11 May 2024 01:29 - 11 May 2024 01:41 #300365 by PCW
Replied by PCW on topic A blast from the past for PCW
Ethernet/Ethercat does not have sufficient isolation for line powered devices
so the original 8I20 architecture with serial interface to a torque mode drive
does make some sense.

Another way is to use isolated gate drivers and say a AMC130M02 for current sensing...
Last edit: 11 May 2024 01:41 by PCW.

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11 May 2024 02:17 #300367 by blazini36
is the serial pin header on the 8i20 isolated? Which header is it, the one on the right side of the PCB i assume?

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