MicroNova Mercury Board - Questions Before Purchase - Page 1
Forum section: electronics / general

author: The_PCB_Guy
author_rank: Regular Contributor
timestamp: January 31, 2018, 07:04:50 pm
content: Regarding the device discussed here:https://www.eevblog.com/forum/buysellwanted/fs-mercury-dip-fpga-module/@mark2112 I am considering purchasing this board but after reviewing the schematic I have a couple of questions:Is there a complete BOM publicly-available, or is that proprietary?For the analog-to-digital conversion I see you use an MCP3008, which is a 5V 8-channel device with an SPI output. Is the FPGA tolerant of the higher voltage output from this ADC (ADC_SCK, ADC_MOSI, ADC_CSN)? I see what appears to be half of a level-shifter for each of these lines (Q2-Q4 with R13-R15) but I do not see any other resistors that I would expect in a standard logic-level translation circuit. Additionally the gate of the NFETs are connected to the HV side, not the LV side as I would have expected. What am I missing?I'm not sure if mark2112 is even still active here but thought I'd give it a go.Thank you,Matt

author: The_PCB_Guy
author_rank: Regular Contributor
timestamp: January 31, 2018, 08:43:12 pm
content: Many thanks for the suggestion. I had actually looked at the Cmod A7-35T board (comparable in physical size and shape to the Mercury) during my search. The only concern is that I plan to design a board around an FPGA and I would like it to have the footprints for the FPGA on-board, but also have the DIP headers to allow the module to be plugged into it. Once the design is complete and functioning I will populate the FPGA circuitry on my board and remove the module. Therefore, I must be able to duplicate much of the circuitry from the module on my motherboard. Unfortunately it appears the Xilinx XC7A35T only comes in BGA packages, which I currently do not have the technology to populate. It's a pretty dumb reason, I know, but for my project this is more important than the number of logic elements. I do not anticipate my program will be all that large, so the Mercury board should be sufficient. I also have experience with the Spartan series of FPGAs, so the Mercury was an obvious choice to begin with. Additionally I really need the 8 ADC channels that are built-in, whereas the Cmod board only has two. I know I could probably put in an external ADC but why bother if there's a board with it already built in that would still suit my needs?I am not set on the Mercury, per se, but it seems to be the best choice for my project at this point.Also, to mark2112, ignore the second question. I figured out the level shifting.

author: The_PCB_Guy
author_rank: Regular Contributor
timestamp: January 31, 2018, 09:10:23 pm
content: All of my development has been based around a 50MHz clock, if that's what you're asking. Once again I have experience with the Spartan, so that is my preferred series at this point.This is a personal project, not a professional one, so I'm not concerned about cloning. In fact it will probably be open source eventually.

author: accelc2018
author_rank: Newbie
timestamp: February 14, 2018, 04:05:21 am
content: One potential candidate would be theMimas Spartan 6 FPGA board. It has FPGA in SMD package, not BGA. Nots sure about running 50MHz signal over the headers though. I guess it could fit your use case.