Lena/Oct 2016: Difference between revisions

There are several main approaches we can use. The first approach is to have multiple FPGAs, each one controlling a set of four magnetometers. The cheapest NI FPGA (7851R) costs $2.8k, equating is $700/channel. The drawback is that the FPGA only has 8 analog inputs and 8 analog outputs, and there are no analog outputs free for the feedback signals. There are still free digital outputs that the FPGA can use to talk to an Arduino over SPI or something similar. Using FPGAs will result in the fastest feedback with proper timing. We don't have the requirements for the feedback to be fast (its band is DC-0.5 Hz as of now) With the signal normalization the FPGA is already close to its limit of slices.

 

 

The third approach would be to use a dedicated microcontroller for each channel. The downside of this approach is that it would take the most of the development time, although the parts would be the cheapest. The microcontroller would need to be chosen very carefully, as many of them don't have enough processing power to process the data (many are 8 bit and don't have a multiplier). Microcontrollers don't typically have high-resolution DACs and ADCs built-in. These would need to either come on a development board and connect to each other, or laid out on a separate board with the microcontroller. Task scheduling would need to be coded by hand, too.

| Controller || PXIe-8840 || - || - || - || -- || 4500

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