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 in one system.
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?