How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers • Hacker News Board

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#21

Post by dragontamer » Thu, Mar 23, 2017, 7:18 PM UTC

zokier wrote: post #15

dragontamer wrote: post #13

Earlier quoted context omitted.

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-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 sound…

Here is just a random FPGA board with onboard 32MB SDRAM. All with whopping $17 BOM according to the author: > Earlier this year, I calculated the part cost of the CAT Board with an HX8K at $17 https://hackaday.io/project/7982-cat-board

SDRAM is a simpler kind of RAM and is likely what would be used in the project of the original post.

I seem to have gotten myself sidetracked by the DDR3 comment, but yeah, going to SDRAM is a practical solution

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#22

Post by jhallenworld » Thu, Mar 23, 2017, 7:19 PM UTC

dragontamer wrote: post #13

revelation wrote: post #12

Earlier quoted context omitted.

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.

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-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 sound…

For $90, get this board:

http://www.latticesemi.com/Products/DevelopmentBoardsAndKits...

Includes 45K LUT FPGA with 250KB on-die RAM, DDR3, controller license and PCIe.. Actually this is so cheap I wonder if they are about to discontinue it.

Anyway, I otherwise think the capture the data with the DMA trick is cool. There are a bunch of projects which do the reverse: generate video with SPI output with tricks to make jitter free sync signals.

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#23

Post by analognoise » Thu, Mar 23, 2017, 7:20 PM UTC

dragontamer wrote: post #13

revelation wrote: post #12

Earlier quoted context omitted.

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.

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-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 sound…

This is extremely outdated bad info.

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#24

Post by dragontamer » Thu, Mar 23, 2017, 7:24 PM UTC

revelation wrote: post #18

dragontamer wrote: post #17

Earlier quoted context omitted.

Erm, you just buy a microcontroller that supports DDR3 out of the box if you care about large amounts of RAM. There are literally thousands of microcontrollers out there, with a configuration for every single possible task imaginable. In contrast, you "contact the sales office" of an IP-block of Verilog and read through a ton of FPGA documentation. I mean, if you really want to just "buy one chip" and do everything w…

I don't think you quite realize what kind of microcontrollers would even come with a DDR3 interface. But if you want to waste away a > 500 MHz chip with sampling GPIO and DMAing that to memory (good luck hitting anything close to what an FPGA could do here, that kind of chip tends to come with multiple levels of caching, pinmuxing, ...) you must have a large BoM and power budget.

Point. I think most of the chips I was thinking about are simpler SDRAM controllers.

Nonetheless, I still think that you're grossly underestimating the needs of the FPGA / Logic Analyzer. The product communicates to the PC over USB for instance, performs RAM-level compression and seems to handle some logic-analyzing tasks as well (considering it natively supports I2C, UART, and the like).

EDIT: I think I see where you're coming from now. The next steps then would be licensing issues then. Like whether or not a company could effectively sell the IP-block of the memory-controller and distribute it over the internet (as what has happened in this project).

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#25

Post by anfractuosity » Thu, Mar 23, 2017, 7:35 PM UTC

dragontamer wrote: post #8

jhallenworld wrote: post #6

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... 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…

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 dat…

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-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).

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#26

Post by fnj » Thu, Mar 23, 2017, 7:51 PM UTC

dragontamer wrote: post #7

megous wrote: post #3

Earlier quoted context omitted.

Perhaps not on Linux. You don't need to run Linux on SBCs. At least not exclusively. Some SBCs also contain additional non-ARM processors on the SoC, which could be used for the purpose of data acquisition. For example Orange Pi has H3, which contains OpenRISC core that can run at 300MHz or so from code located in internal SRAM. I haven't tried yet, but I guess you can get pretty consistent results with this approach…

Well, I was talking about the Raspberry Pi Zero specifically, which doesn't have those RISC cores. One particularly cool Single-board Computer (SBC) is the Beaglebone Blue. The Beaglebone Blue came with "PRUs" (Programmable Realtime Units), which seem similar to the OpenRISC core you are talking about. Such "embedded microcontrollers" exist because the main computer. There are also a hell of a lot more GPIO pins, ADC…

With regard to the PRUs, I don't think the BB Blue has anything the BB, BB Black, and BB Green don't. They all have the PRUs. It's a function of the AM335x Cortex-A8 SoC.

At this point, you need a time machine to get a BB Blue, anyway.

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#27

Post by joezydeco » Thu, Mar 23, 2017, 8:34 PM UTC

vvanders wrote: post #9

jhallenworld wrote: post #6

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... 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…

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

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.

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#28

Post by sysprogs » Thu, Mar 23, 2017, 9:14 PM UTC

megous wrote: post #4

Anyway, excellent project. I hope to try it. :) Have you looked into using opensource protocol analyzers, or adding support for sigrok?

Oh yeah, we looked into the open-source ones. The main problems there were irregular sampling and software that will make you sweat before you get your first reliable measurement. So we wanted to create something that will be extremely easy to use and will reliably work out-of-the-box.

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#29

Post by sysprogs » Thu, Mar 23, 2017, 9:17 PM UTC

jhallenworld wrote: post #6

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... 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…

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.

Re: How We Turned 8 Popular STM32 Boards into Powerful Logic Analyzers

#30

Post by snovv_crash » Thu, Mar 23, 2017, 9:33 PM UTC

dragontamer wrote: post #20

patrickg_zill wrote: post #19

Earlier quoted context omitted.

If you ran a different OS on the Pi, would you get the consistency? For instance, FreeRTOS has been ported (unsure of quality) https://github.com/jameswalmsley/RaspberryPi-FreeRTOS .

You'd get more consistency for sure, but nothing that approaches the 75MHz (13 nanoseconds!!) needed to capture data from the GPIO pins. From my understanding of the Raspberry Pi, the GPIO pins simply weren't designed for that level of speed. Which is fine, the Raspberry Pi was designed for other stuff. Its all about tradeoffs.

Maybe not capture, but you can write to the pins at least that quickly. I've seen projects that use the gpio of a raspberry pi to drive an FM transmitter at 100MHz.