Multichannel microphopne system  - Page 1
Forum section: electronics / projects

author: davidfj12
author_rank: Newbie
timestamp: February 24, 2016, 02:57:41 pm
content: Hello,This is my first postI am creating multi-channel microphone system that has USB interface. I will have 8-channel per board using Cirrus CS5368 ADC with TDM out. The idea is to use a CPLD/FPGA on each board as a FIFO and to make a 16 bit parallel data bus. This bus will be connected to other mic boards and to the GPIF II port on Cypress FX3 eval board which will read data from each board and stream through USB 3.0. I have thought about having a high speed serial bus but I am a little bit afraid of the design problems associated with the high serial clock rate needed and also the GPIF II port on FX3 is limited to 100 MHz clock speed. The end goal is to be able to stream 800-1000 Mbit of data but 50-60 Mbit is enough to start with. Can anybody tell me his opinion on this setup?

author: batteksystem
author_rank: Regular Contributor
timestamp: February 26, 2016, 01:47:28 pm
content: well without a block diagram it is really hard to imagine what's going on

author: Richard Crowley
author_rank: Super Contributor
timestamp: February 26, 2016, 02:00:25 pm
content: What sample rate are you anticipating?What sample size?How many of these 8-channel modules do you anticipate?What are the microphones supposed to be picking up?Are you anticipating having any kind of control of the mic preamp circuits?You talk about total bandwidth, but where are the calculations beginning at the bit-rate per channel?I don't know that there are ANY new designs that use parallel communication either internally or externally.Very high-speed serial technology is sufficient for doing high-definition video. It should be trivial to do audio.What about drivers and software on the other side of that USB3?The basic scheme seems incomplete.Perhaps you should start with a more modest project.

author: davidfj12
author_rank: Newbie
timestamp: February 26, 2016, 07:24:44 pm
content: Thank you for your reply. My description of the project was probably not complete. This is part of my final project in EE and I am not looking for specificsolutions but just some discussions about what I have been thinking about so far.Here are some more info about the project:Sample rate: 192 kHzSample size: 32 bits pr channel in TDM stream with MSB as zero, the actual sample is 24 bitThe goal is to be able to connect up to 16 modules in the future but 1-4 would be the goal to start with.The mic preamps will be on separate boards and I will have MCU and the necessary control lines if I want to be able to control them.The necessary bit rate for each board is 32*8*192kHz = 49.152 Mb/s.I intend to use Cypress FX3 board for USB3 comunication. They have drivers and good tools for making the USB3 communication possible without too much trouble.On the other side I will design software to read from the FX3 board using the drivers from Cypress.My main focus at the moment is to get the TDM data stream to the FX3 module. I totally agree with you about using serial instead of parallel but if I use the FX3 boardI am limited to a clock frequency of 100 MHz at the input port. That is one of the reason to use parallel. The parallel port would have to work at multitues of 3.1 MHz per board.I assumed that that it would be more easy to implement than a very high speed serial communication.But like I said I am just thinking of solutions and its sometimes good to have some input from others.

author: Cerebus
author_rank: Super Contributor
timestamp: February 27, 2016, 02:23:44 am
content: Quote from: davidfj12 on February 26, 2016, 07:24:44 pmGo and hunt down the AES (Audio Engineering Society) standards for transporting digital audio. They're freely downloadable. I'm not suggesting that the AES standards are what you should necessarily implement, but looking at how these problems have been solved before might give you something to think about. e.g. Synchronising multiple mic channels multiplexed onto a wire and then synchronising that with another bunch of mic channels multiplexed down another wire.

author: davidfj12
author_rank: Newbie
timestamp: February 27, 2016, 02:55:38 pm
content: Thank you for your suggestion. I will check out the AES standards to get some ideas.