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

SPI interface coming off that PIC and some *special* firmware, I think it'd be a different beast....

.....just sayin lol

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

PCW wrote:

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.
 

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.

 

PCW wrote:

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?

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...

is the serial pin header on the 8i20 isolated? Which header is it, the one on the right side of the PCB i assume?