Right size FPGA

Question

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

johnbeetem · Accepted Answer

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 . 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.

shabaz · Answer

Hi Mike,

Yes, ISE is the correct software package. By the way, there is the 'coolrunner-II' family too, which is surface-mount only, but has the benefit of handling level conversion too, e.g. 5V<->3.3V (don't know if the other CPLD families do that). They are about the same price I think.

Right size FPGA

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