Prototype: LogiStart MegaWing

Jack Gassett

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Hey everyone, I've been working on a new MegaWing design that is meant as a low cost, open source MegaWing for people who want to experiment with digital logic. Mike Field wrote this great VHDL tutorial where he wants to use the Papilio, except for the Papilio doesn't have the things he needs like slide switches. This MegaWing gives these tutorials and anyone who wants to experiment with Digital logic a collection of hardware to play with.

This is my first attempt at the board and I'd appreciate any input from the community. I'm also tentatively calling it the LogiStart MegaWing but would appreciate feedback on the name too. :)

The board has the following hardware:

  • 8 channel 12-bit SPI ADC
  • 8-bit (3r, 3g, 2b) VGA.
  • Mono audio jack that feeds to left and right outputs.
  • 8 slide switches
  • 8 LED's
  • Micro Digital Joystick with 4 directions and select
  • 7 Segment display with control over A-G and DP segments.

The source code can be found on Github, and a pdf of the schematic can be found here.


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Looks great.

A question, on the audio part : why is the resistor *after* the cap ? Not being an expert (at all) in analog electronics, I would have put it between the digital output and the cap, to prevent the cap from drawing/sinking big currents on level changes.

For the name : Papiliogic ? (ok, that really sucks)

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dunno.  i kind of like 'LogicStart' as seems to imply that it is for newbies

to work with where as a lab is usually something with a bunch of stuff

that i probably know nothing about..

both are accurate i guess, but one makes me want to buy it,

while the other says, prepare to be overwhelmed.

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Just an idea, but I think a great getting started component that could go with this is an LCD screen, like on some of Digilent's fpga boards. It seems that the common things for getting started are slide switches, push buttons, LEDS, and LCD screens. If there was a way to fit one on this wing I think that would be cool.


edit: At first I was only looking at the layout in the post above, and not on github. I did not see the seven segment display at first. I guess it would only fit one or the other

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Hey John,

I actually did 4 different layouts to see how they came together with space/pin numbers/looks. The different approaches I took were:

  • A board that didn't have any display but left a 16-bit Wing slot open so either a LCD or 7segment display could be attached. Or any other Wing for that matter.1.PNG

  • Another board that used a LCD instead of 7 segment display:lcd.PNG

I liked the first design but I always worry that people won't want to hassle with Wings for something like this. The second design extended out past the Papilio One FPGA and just didn't look as nice and clean as using a 7 segment display did.

Any thoughts?


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  • 2 weeks later...
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Ha! That gave me a good chuckle. :)

With all the different hardware I've had Pacman running on I've gotten pretty good at it because I always get sucked into playing it for a while. I was trying to keep the video short so I was actually chasing the ghosts around trying to get killed and I sucked pretty bad at that. ;)

Thanks for the post and the razzing.



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  • 2 weeks later...

Hello Mike,

It is a ADC128S102 datasheet - 12-bit, 8 channel 1 Msps serial ADC. I was trying to read the part number off a SPI Wing last night and had the same problem.

It is based off the SPI Wing which has some more information here:


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  • 4 months later...

Hi Jack,

I like my pretty red shiny board...

I'm sure that the latest UCF file for Papilio One + LogiStart has errors in it. The switches and LEDs are the wrong way around.... The constraints below are working for me on a project (or is it just because I'm using a -250 board?)

# Wing2 Column C

NET "W2C<0>" LOC = "P91" ; # LogicStart Switch 7

NET "W2C<1>" LOC = "P92" ; # LogicStart Switch 6

NET "W2C<2>" LOC = "P94" ; # LogicStart Switch 5

NET "W2C<3>" LOC = "P95" ; # LogicStart Switch 4

NET "W2C<4>" LOC = "P98" ; # LogicStart Switch 3

NET "W2C<5>" LOC = "P2" ; # LogicStart Switch 2

NET "W2C<6>" LOC = "P3" ; # LogicStart Switch 1

NET "W2C<7>" LOC = "P4" ; # LogicStart Switch 0

NET "W2C<8>" LOC = "P5" ; # LogicStart LED 7

NET "W2C<9>" LOC = "P9" ; # LogicStart LED 6

NET "W2C<10>" LOC = "P10" ; # LogicStart LED 5

NET "W2C<11>" LOC = "P11" ; # LogicStart LED 4

NET "W2C<12>" LOC = "P12" ; # LogicStart LED 3

NET "W2C<13>" LOC = "P15" ; # LogicStart LED 2

NET "W2C<14>" LOC = "P16" ; # LogicStart LED 1

NET "W2C<15>" LOC = "P17" ; # LogicStart LED 0


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