5 ms·

8 Boards? How about turn one FPGA board into a logic analyzer. For example, get the $25 MachXo3LF starter kit: http://www.latticesemi.com/Products/Developmen

8 Boards? How about turn one FPGA board into a logic analyzer. For example, get the $25 MachXo3LF starter kit: http://www.latticesemi.com/Products/DevelopmentBoardsAndKits/MachXO3LFStarterKit.aspx http://www.latticesemi.com/Products/DevelopmentBoardsAndKits... And that's pretty much it- Lattice includes "Reveal" a logic analyzer which can run on the FPGA in their tools. It's intended to debug designs, but there is nothing stopping you from capturing data from pins. Pretty sure it would capture signals up to ~200 MHz. http://media.latticesemi.com/~/media/LatticeSemi/Images/ProductImages/DesignSoftwareandIntellectualProperty/Diamond/featuresreveal.JPG?la=en&d=20140819T155508 http://media.latticesemi.com/~/media/LatticeSemi/Images/Prod... (it would be a lot better if it had a superspeed USB connection- they should make a version with Cypress FX3)

dragontamer 10y ago
And how much RAM does that FPGA hold? When your entire chip is programmable-logic, you don't have much room for RAM. The MachXo3LF-6900 has a grand total of 240 kBITs, or 30kBytes of storage. In contrast, the STM32F746G will get you 320kBYTES of storage, 10x the capacity. At 75MHz and 1-bit per cycle, that's still only 35ms of storage. Furthermore, it'd be a lot easier to program a Microcontroller to compress the data as its reading it, rather than use the FPGA. The Microcontroller will still get you the Ethernet and USB connections too. -------- I think this is a job for a microcontroller, not an FPGA. FPGAs are nice and flexible of course, but Microcontrollers offer you far more performance if you're going to use the specific features. The STM32F746G has GPIO -> DMA directly to its RAM, while the CPU can compress 1/2 of the signal and send it out while the GPIO pins are simultaneously working. That's... pretty good. I have doubts that a cheap FPGA can accomplish all that at the same speed.
- vvanders 10y ago
  > I have doubts that a cheap FPGA can accomplish all that at the same speed. A cheap FPGA can probably do that at 5x the speed. Parallel operations like these are specifically what they're build for.
  - dragontamer 10y ago
    Speed isn't the only consideration here. 5x the speed needs 5x the RAM to store it in. But FPGAs will NEVER have as much RAM as a dedicated microcontroller. Again, you're looking at ~320kBytes on the $25 STM32 microcontroller board, against ~30kBytes on the $25 FPGA board. With 1/10th the RAM, the FPGA will store far less useful data. The typical Oscilloscope is like 100MHz. Getting a cheap 75MHz logic analyzer is perfectly acceptable. Storing and processing all that data (ie: outputting it to an Ethernet port) start to become the main issues once the speed issue is solved. In my experience, those small FPGAs run out of room rather quickly too. Throw down something as simple as a Wallace tree multiplier and suddenly half your LUTs are eaten up.
    - revelation 10y ago
      What are you even talking about? FPGAs routinely interface with DDR3 and other "big buckets of memory" should you need them. Try that with your STM32.
      - dragontamer 10y ago
        What price point are we talking about here? Throw down a single DDR3 Memory chip, and you've already eaten up like half the $25 hardware budget. http://www.digikey.com/product-detail/en/micron-technology-inc/MT41K512M8DA-107-AIT-P/557-1762-ND/6036290 http://www.digikey.com/product-detail/en/micron-technology-i... The "embedded" solution is: buy embedded on-board SRAM when you need it, and if necessary, buy an embedded on-board SRAM memory controller if you need it. Building your own memory-controller out of an FPGA sounds like hell to layout. Anyway, if we're talking about cheap stuff, DDR3L isn't the technology of note. This is about simpler SDRAM-level stuff, maybe a few MB at a time is sufficient. ---- Furthermore: How many LUTs will your memory controller take up? http://www.latticesemi.com/en/Products/DesignSoftwareAndIP/IntellectualProperty/IPCore/IPCores01/DDR3SDRAMController.aspx#_D5983CCD053543DA9E0D5AC1F76E34D4 http://www.latticesemi.com/en/Products/DesignSoftwareAndIP/I... According to this, Lattice's DDR3L 16-bit memory controller is 2500 LUTs. The $25 FPGA only has 6300-LUTs, so you've already used up 40% of the chip on just memory-interfacing! Yeah, you can accomplish a lot with a $600 FPGA with a Million-bajillion-LUTs and embedded cores. But at the $25 price point, FPGAs often run out of room. You don't have many LUTs to work with. Dollar-for-dollar, a microcontroller will outperform an FPGA in most tasks. That's just the facts. ASIC-implemented memory-controllers and ASIC-implemented large banks of internal SRAM just work better for computer-like tasks. FPGAs should be used for custom logic that isn't typically handled by a microcontroller / microprocessor. Not memory-controllers and ALUs that already exist in an easily packaged form. There's a reason why high-level FPGAs have embedded ARM cores and embedded memory-controllers in them (alas: such technology is likely out of the reach of cheap $25 FPGAs)
- anfractuosity 10y ago
  Have a look at the Saleae logic analysers for example, they combine an FPGA with an EZ-USB FX3, in the case of the Logic Pro 8. http://www.eevblog.com/forum/testgear/saleae-logic-pro-8-quick-teardown/ http://www.eevblog.com/forum/testgear/saleae-logic-pro-8-qui... I believe the FPGA is often being used for converting fewer high speed inputs, to a greater number of lower speed outputs for the GPIO of the FX3, I think that's called SerDes (please correct me if I'm using that phrase incorrectly).
vvanders 10y ago
Yup, Saleae logic series also makes fantastic, if a little more expensive ones. The next step up starts getting into the $x,000 range.
- joezydeco 10y ago
  Saleae also has better ESD and voltage protection on their units than this EVB does. I'd be afraid to see what -15VDC does on some of these GPIO pins. Plus the newer units can also have 1 or more analog channels. While having a live view of the data would be nice, I've found that 99% of my work with the Logic doesn't really need it.
sysprogs 10y ago
Sure, an FPGA does the job faster, but how popular are the FPGA boards compared to something like STM32 Nucleo? What we are trying to achieve is make a software logic analyzer that will work on top of the hardware that everyone has for prototyping anyway. 8 boards is just the beginning... And yes, USB3.0 Cypress FX3 is in our short list.
grkvlt 10y ago
The logic analyser just uses a single board, but they support 8 different STM32 development kit boards.

dragontamer 10y ago

And how much RAM does that FPGA hold? When your entire chip is programmable-logic, you don't have much room for RAM. The MachXo3LF-6900 has a grand total of 240 kBITs, or 30kBytes of storage. In contrast, the STM32F746G will get you 320kBYTES of storage, 10x the capacity. At 75MHz and 1-bit per cycle, that's still only 35ms of storage. Furthermore, it'd be a lot easier to program a Microcontroller to compress the data as its reading it, rather than use the FPGA. The Microcontroller will still get you the Ethernet and USB connections too. -------- I think this is a job for a microcontroller, not an FPGA. FPGAs are nice and flexible of course, but Microcontrollers offer you far more performance if you're going to use the specific features. The STM32F746G has GPIO -> DMA directly to its RAM, while the CPU can compress 1/2 of the signal and send it out while the GPIO pins are simultaneously working. That's... pretty good. I have doubts that a cheap FPGA can accomplish all that at the same speed.

vvanders 10y ago
> I have doubts that a cheap FPGA can accomplish all that at the same speed. A cheap FPGA can probably do that at 5x the speed. Parallel operations like these are specifically what they're build for.
- dragontamer 10y ago
  Speed isn't the only consideration here. 5x the speed needs 5x the RAM to store it in. But FPGAs will NEVER have as much RAM as a dedicated microcontroller. Again, you're looking at ~320kBytes on the $25 STM32 microcontroller board, against ~30kBytes on the $25 FPGA board. With 1/10th the RAM, the FPGA will store far less useful data. The typical Oscilloscope is like 100MHz. Getting a cheap 75MHz logic analyzer is perfectly acceptable. Storing and processing all that data (ie: outputting it to an Ethernet port) start to become the main issues once the speed issue is solved. In my experience, those small FPGAs run out of room rather quickly too. Throw down something as simple as a Wallace tree multiplier and suddenly half your LUTs are eaten up.
  - revelation 10y ago
    What are you even talking about? FPGAs routinely interface with DDR3 and other "big buckets of memory" should you need them. Try that with your STM32.
    - dragontamer 10y ago
      What price point are we talking about here? Throw down a single DDR3 Memory chip, and you've already eaten up like half the $25 hardware budget. http://www.digikey.com/product-detail/en/micron-technology-inc/MT41K512M8DA-107-AIT-P/557-1762-ND/6036290 http://www.digikey.com/product-detail/en/micron-technology-i... The "embedded" solution is: buy embedded on-board SRAM when you need it, and if necessary, buy an embedded on-board SRAM memory controller if you need it. Building your own memory-controller out of an FPGA sounds like hell to layout. Anyway, if we're talking about cheap stuff, DDR3L isn't the technology of note. This is about simpler SDRAM-level stuff, maybe a few MB at a time is sufficient. ---- Furthermore: How many LUTs will your memory controller take up? http://www.latticesemi.com/en/Products/DesignSoftwareAndIP/IntellectualProperty/IPCore/IPCores01/DDR3SDRAMController.aspx#_D5983CCD053543DA9E0D5AC1F76E34D4 http://www.latticesemi.com/en/Products/DesignSoftwareAndIP/I... According to this, Lattice's DDR3L 16-bit memory controller is 2500 LUTs. The $25 FPGA only has 6300-LUTs, so you've already used up 40% of the chip on just memory-interfacing! Yeah, you can accomplish a lot with a $600 FPGA with a Million-bajillion-LUTs and embedded cores. But at the $25 price point, FPGAs often run out of room. You don't have many LUTs to work with. Dollar-for-dollar, a microcontroller will outperform an FPGA in most tasks. That's just the facts. ASIC-implemented memory-controllers and ASIC-implemented large banks of internal SRAM just work better for computer-like tasks. FPGAs should be used for custom logic that isn't typically handled by a microcontroller / microprocessor. Not memory-controllers and ALUs that already exist in an easily packaged form. There's a reason why high-level FPGAs have embedded ARM cores and embedded memory-controllers in them (alas: such technology is likely out of the reach of cheap $25 FPGAs)
anfractuosity 10y ago
Have a look at the Saleae logic analysers for example, they combine an FPGA with an EZ-USB FX3, in the case of the Logic Pro 8. http://www.eevblog.com/forum/testgear/saleae-logic-pro-8-quick-teardown/ http://www.eevblog.com/forum/testgear/saleae-logic-pro-8-qui... I believe the FPGA is often being used for converting fewer high speed inputs, to a greater number of lower speed outputs for the GPIO of the FX3, I think that's called SerDes (please correct me if I'm using that phrase incorrectly).

vvanders 10y ago

Yup, Saleae logic series also makes fantastic, if a little more expensive ones. The next step up starts getting into the $x,000 range.

joezydeco 10y ago
Saleae also has better ESD and voltage protection on their units than this EVB does. I'd be afraid to see what -15VDC does on some of these GPIO pins. Plus the newer units can also have 1 or more analog channels. While having a live view of the data would be nice, I've found that 99% of my work with the Logic doesn't really need it.

sysprogs 10y ago

Sure, an FPGA does the job faster, but how popular are the FPGA boards compared to something like STM32 Nucleo? What we are trying to achieve is make a software logic analyzer that will work on top of the hardware that everyone has for prototyping anyway. 8 boards is just the beginning... And yes, USB3.0 Cypress FX3 is in our short list.

grkvlt 10y ago

The logic analyser just uses a single board, but they support 8 different STM32 development kit boards.