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How to manage 120*8*16 microcontrollers?
JohanHoltby:
Hi!
I'm designing a 40 ports Solid state relay switch and I need to monitor each port for voltage and current at about 1Ms/S. I would also like to store the streaming data in an SDRAM (3.3V compatible) for the last 8 seconds. So using a 128Mbit should do.
My initial idea is to use two 30-50 cent microcontrollers, one for current and one for voltage (one to high side and one to low side of the SSR driver) and then let them output 8bit each to the the memory pins and then have a third IC to control the Memory addressing. All this three would run in sync using some common clock source.
To add on this I will stack this boards. To about 8 boards in total and could probably have around 16 of this stacks.
So this would leave me with about 120 microcontrollers and that would give me three challenges:
Which bus should I use? I could decide to only communicate with the Memmory chip that would reduce it to 40.
Since I will run sensitive analog signals through this board will I have problems or will it be solvable with a multi layer board?
How do I program them? Is JTAG dasychain the only option other that some switching needle bed?
Is there a better way to do it?
MosherIV:
Hi. You are suggesting a 'polling' type scheme, where you store all the results in the RAM. This results in a bandwidth problem. Hence your questiin about whuch bus and protocol
Try changing the problem around. Instead of polling try a interrupt scheme.
In other words, only send information when there is a state change.
This should reduce the bandwidth if the state/current/voltage does not change often.
This will allow lower requirements for the bus and protocol.
OM222O:
128Mbit * 120 micros = 15360Mbit/s = 15Gbit/s
call me crazy but at a lot of places you can't get more than Gigabit internet ... your application requires 2 10Gbit connections. that's just to put things in perspective. why do you want to sample at such a high rate for 40 ports at the same time? even then, why would you want to share that data with another computer / MCU / etc. ?
the only thing I can think of would be an electronic fuse for over voltage / over current protection but that doesn't require sharing that info :-//
Siwastaja:
By solid state relay, you mean power line AC?
Are you really sure you want to sample at such rate? What information are you expecting to see at such high frequencies?
coromonadalix:
Im doing almost the same thing with 3x usb NiDac 16 input ports (each), i monitor rf output of the boards i test, they are medical grade/certified boards.
It consume lots of ressources to get the job going, i had to slower the sample rate, now at 1 measurment in 3 seconds interval each board, i was doing it a 1 sec intervals loll and save the log into a text file and a bitmap for ISO purposes ...
The only safety i use is: a countdown timer, it will cut off all the tests past the software programmed cycle, and for added protection, all the DC supplies line are short protected and fused in case of ...
I do this on a dual core pc 4gb ram with an oooold windows XP loll The software was custom made for us, but no updates since :(
And as other replied, why do you need to measure up to 1ms/sec ??? is it too critical ??
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