Author Topic: MicroNova Mercury Board - Questions Before Purchase  (Read 829 times)

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Offline The_PCB_Guy

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MicroNova Mercury Board - Questions Before Purchase
« on: January 31, 2018, 07:04:50 pm »
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
« Last Edit: January 31, 2018, 07:32:58 pm by The_PCB_Guy »
The_PCB_Guy
 

Online blueskull

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Re: MicroNova Mercury Board - Questions Before Purchase
« Reply #1 on: January 31, 2018, 08:23:11 pm »
It has ~4k LEs, which by today's standard is very low end. Lattice has a lot of cheaper, smaller boards at this density.
If you are looking for the same price, then there are Digilent Artix 7 boards, you can get 9x the logic density for the same price.
 
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Offline The_PCB_Guy

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Re: MicroNova Mercury Board - Questions Before Purchase
« Reply #2 on: January 31, 2018, 08:43:12 pm »
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.
The_PCB_Guy
 

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Re: MicroNova Mercury Board - Questions Before Purchase
« Reply #3 on: January 31, 2018, 08:56:04 pm »
What kind of speed you are looking at? If you are not looking for very high logic speed, consider Lattice iCE40 and iCE5 product line. They have 4k/5k/8k logic density. Also, consider Lattice MachXO3 product line, they have 4k/7k/9k logic density, faster than iCE family, with higher static power consumption. Still way "greener" than Spartan 3.

All of those Lattice small density FPGAs have built in flash or nvcm, so you don't have to worry about people dumping your bitstream and make clones.

Recently, Altera/Intel has also jointed the low density arena, with their Max 10 and Cyclone 10 LP. Go check them out.

Some iCE40 and iCE5 are in QFN package. Some Altera parts are in QFP package. They all have original factory or third party gum stick boards for prototyping.

Disclaimer: I'm a happy Lattice user with occasional Altera usage.
 

Offline The_PCB_Guy

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Re: MicroNova Mercury Board - Questions Before Purchase
« Reply #4 on: January 31, 2018, 09:10:23 pm »
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.
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Offline accelc2018

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Re: MicroNova Mercury Board - Questions Before Purchase
« Reply #5 on: February 14, 2018, 04:05:21 am »
One potential candidate would be the Mimas 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.
« Last Edit: February 15, 2018, 03:11:58 am by accelc2018 »
 


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