On 12/23/2010 03:05 AM, Chris Albertson wrote:
I used a shared opto-isolated async bus. You need two optocouplers
per microcontroller, and one place you power the shared bus, and
you're all set.
I have yet to see an microcontroller without an async port.
Opto-isolater? Why not just use fiber cable between cards. I know
it sounds exotic but also seems to have half the parts count. those
s/pdif jacks are so cheap and I bet you can use them as pretty much
drop in replacements for opto-isolators. Would s/pdif jacks work as a
physical layer?
Really I just used I2C in my write-up as a place holder. I you say
nothing no one ever says a blank paper is wrong and suggests something
better.
Using a serial interface is nice, but I2C is not the one of my
choosings. I'd go for plain serial interface, RS-232 like, but not
necesserilly with RS-232 levels. Possibly using RS-485. A party line has
several issues with it, but reduces the cost. It's more suitable for
control than pumping data out of the device.
s optical isolation required when all the modules are sharing a common
power supply? Does this means all the coax connectors need to be
isolated. I guess some one better step up and propose a grounding
scheme. That's not going to be me.
Within such a situation, RF-chokes and transoformers would suffice for
isolation. Optical isolation using normal opto-couplers is cheap and
space-saving considering that for most uses there just isn't much of
data-speed except for a few things.
Cheers,
Magnus
On 12/23/2010 03:05 AM, Chris Albertson wrote:
> On Wed, Dec 22, 2010 at 3:32 PM, Poul-Henning Kamp<phk@phk.freebsd.dk> wrote:
>
>> I used a shared opto-isolated async bus. You need two optocouplers
>> per microcontroller, and one place you power the shared bus, and
>> you're all set.
>>
>> I have yet to see an microcontroller without an async port.
>
> Opto-isolater? Why not just use fiber cable between cards. I know
> it sounds exotic but also seems to have half the parts count. those
> s/pdif jacks are so cheap and I bet you can use them as pretty much
> drop in replacements for opto-isolators. Would s/pdif jacks work as a
> physical layer?
>
> Really I just used I2C in my write-up as a place holder. I you say
> nothing no one ever says a blank paper is wrong and suggests something
> better.
Using a serial interface is nice, but I2C is not the one of my
choosings. I'd go for plain serial interface, RS-232 like, but not
necesserilly with RS-232 levels. Possibly using RS-485. A party line has
several issues with it, but reduces the cost. It's more suitable for
control than pumping data out of the device.
> s optical isolation required when all the modules are sharing a common
> power supply? Does this means all the coax connectors need to be
> isolated. I guess some one better step up and propose a grounding
> scheme. That's not going to be me.
Within such a situation, RF-chokes and transoformers would suffice for
isolation. Optical isolation using normal opto-couplers is cheap and
space-saving considering that for most uses there just isn't much of
data-speed except for a few things.
Cheers,
Magnus
