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Right size FPGA

mconners

Hi everyone,

 

I had a looked at schematic calling for discrete components to allow a RasPi to interface to a SainSmart 3.2 LCD.

 

The design consisted of 3 74HCT4094's, and 1 74HCT404 counter.

 

Schematic here : http://i0.wp.com/ozzmaker.com/wp-content/uploads/2013/10/sainsmartschematicV2.png

 

I didn't have the discrete's laying around, but I did have one of these: http://www.amazon.com/EP2C5T144-Altera-Cyclone-Development-Board/dp/B007YDTTEY/ref=sr_1_1?ie=UTF8&qid=1399140473&sr=8-1&keywords=altera+cyclone+ii

 

I had been wanting to bone up on FPGA design/implementation as the last time I messed with programmable logic was in the early 90's using ABEL on some small cypress(I think) chips. I had brief exposure to XILINX parts, they were fairly new at the time, and before long I moved off to do software full time and left my hardware days in the dust. Until recently. But now it's a hobby.

 

I basically created 2 components in verilog, a 5 bit up counter, and a 24 bit serial shift buffer, wired up the internal gozintas to gozoutas. My design works, I tested it with an O'scope and logic analyzer. Given specific inputs, I get the ouputs I want. I know you can do some of that in simulation, but I didn't bother for right now.

 

Anyway, my question is, this FPGA is obviously way more than I need for this design.

 

The Quartus compiler output is as follows:

 

Family                             ; Cyclone II                               ;

; Device                             ; EP2C5T144C8                              ;

; Timing Models                      ; Final                                    ;

; Total logic elements               ; 59 / 4,608 ( 1 % )                       ;

;     Total combinational functions  ; 11 / 4,608 ( < 1 % )                     ;

;     Dedicated logic registers      ; 54 / 4,608 ( 1 % )                       ;

; Total registers                    ; 54                                       ;

; Total pins                         ; 28 / 89 ( 31 % )                         ;

; Total virtual pins                 ; 0                                        ;

; Total memory bits                  ; 0 / 119,808 ( 0 % )                      ;

; Embedded Multiplier 9-bit elements ; 0 / 26 ( 0 % )                           ;

; Total PLLs                         ; 0 / 2 ( 0 % )   

 

Does anyone know if there is a utility in Quartus, or anywhere else for that matter,  that can look at my design an suggest a proper sized part? I'm not beholden to Altera or Quartus, but at the moment it is what I have the most recent experience with. I'd consider other tools.

 

I can build this with cheap discretes, but if there is a single chip programmable solution that is inexpensive, I could save board real estate, reduce external complexity, yadda, yadda, yadda...

 

The only thing on this chip that I am making any significant use of is pin count, and I could reduce that to about 25 if necessary.

 

I appreciate your consideration,

 

Mike

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  • 0

    Hi Mike,

     

    Most of my experience is with Xilinx.  On their tools, you can select a part family rather than a specific part, and I think it it will automatically choose the one that fits.  I do FPGA design professionally, so I've developed a decent amount of experience for getting a ball-park figure of which part will fit.  Then I design the logic, synthesize it, and make sure it fits with plenty of room for changes.  I also try to select several parts with the same package and pinout so that if the design needs a lot more logic we can switch to the larger part without PCB changes.

     

    For a small amount of logic, I'd suggest looking at the Guzunty Pi board, which uses a 72-macrocell Xilinx XC9572XL.  This CPLD has been around a long time but IMO is still a nice, cheap part for small amounts of logic.  The 9572XL and its smaller brother the 9536XL are the only CPLDs I know of that you can still get in a PLCC package (50 mil pin pitch).  They are really easy to solder, and you can get sockets with 0.1" pin spacing, and even use wire-wrap image.  The Guzunty Pi is actually available in kit form, with all through-hole parts.  It plugs into a Raspberry Pi.

     

    For a little larger, the Silicon Blue parts from Lattice are pretty attractive: iCE40 series.  I haven't tried them myself, but they look like a great part for small-to-medium amounts of logic with built-in configuration memory.

     

    For even larger, the Xilinx Spartan-3E and Spartan-3A are quite nice.  I just acquired a Papilio One board for US$38 with Xilinx XC3S250E, equivalent to an ASIC with approx 250K gates.  It's probably around the same capabilities as your Cyclone II part.

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  • 0

    Hi Mike,

     

    Most of my experience is with Xilinx.  On their tools, you can select a part family rather than a specific part, and I think it it will automatically choose the one that fits.  I do FPGA design professionally, so I've developed a decent amount of experience for getting a ball-park figure of which part will fit.  Then I design the logic, synthesize it, and make sure it fits with plenty of room for changes.  I also try to select several parts with the same package and pinout so that if the design needs a lot more logic we can switch to the larger part without PCB changes.

     

    For a small amount of logic, I'd suggest looking at the Guzunty Pi board, which uses a 72-macrocell Xilinx XC9572XL.  This CPLD has been around a long time but IMO is still a nice, cheap part for small amounts of logic.  The 9572XL and its smaller brother the 9536XL are the only CPLDs I know of that you can still get in a PLCC package (50 mil pin pitch).  They are really easy to solder, and you can get sockets with 0.1" pin spacing, and even use wire-wrap image.  The Guzunty Pi is actually available in kit form, with all through-hole parts.  It plugs into a Raspberry Pi.

     

    For a little larger, the Silicon Blue parts from Lattice are pretty attractive: iCE40 series.  I haven't tried them myself, but they look like a great part for small-to-medium amounts of logic with built-in configuration memory.

     

    For even larger, the Xilinx Spartan-3E and Spartan-3A are quite nice.  I just acquired a Papilio One board for US$38 with Xilinx XC3S250E, equivalent to an ASIC with approx 250K gates.  It's probably around the same capabilities as your Cyclone II part.

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