@asmi @zygot @JColvin
Thank you for your kind responses, appreciated :)
I am sorry for the lack of details. Let me start by answering the questions:
1. Data source - How are you going to do the capture? Is it going to be a crap ton of ADCs, or some fast multichannel ADCs, or maybe something else?
I am planning to use PDM MEMS microphones and group every 8 PDM signals into 1 TDM signal. I am not sure if there is one that can convert 16 PDM signals to 1 TDM signal, maybe I can tristate two TDM signals into one output stream.
2. Data input - Whatever you settle on in (1), how this data is going to be fed into FPGA? SPI, I2S, or some custom bus? This will help you determine which and how many pins will you require from FPGA, which can disqualify a lot of FPGA boards because they won't have suitable connectivity.
I think I2S interface would be a good for TDM signal. However, the number of I2S interfaces would be limited. If 128 sensor is too many, I guess I can lower the number to 64 sensors. I wish there is an alternative to follow. I am open for any suggestion.
3. Data processing - Once the question if bringing data into FPGA is resolved, what exactly are you going to do with that data inside FPGA? That has a major implications on a FPGA family and density that you require.
One reason to work with the FPGA is to bring large matrix calculations. The input data contains information of amplitude, time, and position. Therefore, it should be put in the shift registers and arranged in a matrix that represents spatial distribution. Then matrix multiplications are performed to fit the data into the model which is representated by multiple transfer function matrices.
4. Data output - And finally, once you've done all the processing inside FPGA, what are going to be your outputs? This again can disqualify some boards because they lack the output method of your choice.
I like to stream out the output to a MCU or GPU that further processes the output data and presents it as the final output format.
Here are my responses for the other comments
In general Digilent FPGA boards are designed to support their PMOD ecosystem, and are IO pin deficient. They do sell a couple of boards with 1 FMC connector but finding an off-the-shelf mezzanine card that supports 128 undefined sensors is going to be a problem. Even if you can list all of the exact sensors by part number an answer is not likely to be a simple one.
You are right, I do not think PMOD ecosystem is sufficient. I am actually considering the FMC connector because I found a commercial product (with xylinx FPGA board) that manages to handle +100 sensors with a couple of FMC connectors. But, I really want to avoid design complexity.
What do you think about SYZYGY connector?
Usually, for low Fs, multiple channel ADC applications, analog inputs to the sampler(s) are time mutiplexed. Are you prepared to do some digital and analog design and prototype construction?
I guess I could not avoid multiplexing and demultiplexing. I want to groups some sensors to simplify prototype structure; for that reason I choose PDM-based sensor and PDM to TDM signal converters.
@zzzhhh
Thank you for your recommendation. I will check the Arty A7-100T.