5 ms·

real quite high level sorry, most of your embedded projects going forward are MCU+fpga to do what? I thought a custom router but 284mbps isn't nearly fast for a

real quite high level sorry, most of your embedded projects going forward are MCU+fpga to do what? I thought a custom router but 284mbps isn't nearly fast for a network.

UncleOxidant 2y ago
It's a good question. A lot of FPGA projects I see (including some real life products I've looked into recently) don't really need an FPGA. One I was asked to evaluate recently could easily have been done with a microcontroller with PWM outputs. The frequencies involved were well under 40MHz. Yes, there were a couple of multiplications going on in the FPGA, but there those could've been easily handled by a micorcontroller. An RP2040 would've sufficed instead of what they had - a microcontroller + an FPGA.
- azonenberg 2y ago
  The projects in question include things like a 48 port gigabit Ethernet switch with packet datapath in the FPGA, and dual 10/25G SFP28 uplinks. You're not doing that on a MCU. Also higher end oscilloscope work (e.g. 10 Gsps 12-bit JESD204B) But a STM32 is more than sufficient for the management interface on both.
- rvense 2y ago
  I think a lot of people don't fully appreciate how fast a modern "microcontroller" is. That 'H735 is probably faster than every computer I had up to and including the iBook G4 I until early 2009.
  - buescher 2y ago
    I keep running into that also. It's like the common mental model of a microcontroller froze around Y2K as a sort of headless VIC-20. I had an FAE, and a good one, from a major supplier tell me "you can't implement a filter" on a low-end micro that was roughly as powerful as an early nineties DSP.
    - rvense 2y ago
      Cortex-Ms, man. A lot of 'em you just give 3.3V and a couple of bypass caps, and GCC will use the single-cycle hardware MAC (for M4 and above) if you just write the straight-forward C code and you can put it on there in 600ms with DFU. I'm a hobbyist, not an embedded wizard, but it really seems *pretty* good compared to what I understand about the old days. (Like I like retro stuff and during COVID I bought an old DSP56k dev board with a book about the assembly language but oh boy, oh dear)
      - buescher 2y ago
        They're amazing. And - you can run a PC emulator on an ESP32. Sure, you need the fancy ram. OK. And then people will tell me an ESP32 can't do things that people definitely were doing on bare-bones PCs in the eighties.
- 15155 2y ago
  Zynq 7010s are $2.50 and are a hell of a lot more chip than an RP2040. If you already have the design (or copy one of the 50 available), it's a good option when you don't want to fight the chip. PIO has extraordinarily sloppy timing (skew in all categories) compared to the cheapest and smallest FPGAs.
  - azonenberg 2y ago
    Where are you getting them for $2.50?? The XC7Z010-1CLG225C is $74.83 at Digikey in qty 1. Checking sketchier places Win-Source has the CLG400 package for $22.20 and even the cheapest aliexpress seller wants $4.84 for something marked as a 7Z010 that may or may not be legit. Also "fight the chip" is pretty much the definition of what I did last time I did a zynq project. Just give me a plain FPGA and MCU with no wizards or GUIs or automatic code generation.
    - 15155 2y ago
      https://www.aliexpress.us/item/3256803970893483.html https://www.aliexpress.us/item/3256803970893483.html I've ordered trays (and they send the OEM tray) - unique barcodes, legit. > Just give me a plain FPGA and MCU with no wizards or GUIs or automatic code generation. You can pretty much cut out all of their tools and get a pure Yocto/Vivado TCL build for the bitstream for the 7 series Zynqs. Very low touch. Their IO planner (in the Vivado IP integrator) is somewhat necessary for complex peripheral scenarios and is one of the few things I ever use Xilinx GUI applications for anymore.
      - anyfoo 2y ago
        I don’t even find Vivado that bad, but maybe I have Stockholm syndrome. Or maybe it’s because I’m forced to use Intel Quartus right now and wish it was Vivado every time.
      - scottapotamas 2y ago
        I was interested to see, or at least what state they're in so I grabbed a couple. Might try to compare them against some genuine ones with CT and destructive inspection. On the chance they're half reasonable, thanks for the link.
azonenberg 2y ago
The intent is for the high performance datapath to live entirely in FPGA (and the project you're probably thinking of is switching, not routing). The MCU is for control plane only. Several hundred Mbps between the control and data plane is more than enough for a SSH management CLI and poking registers on the FPGA to move a port to a different VLAN in response to a CLI command or add an ACL rule or something.
deleted 2y ago
[deleted]
dragontamer 2y ago
Embedded projects are never about doing things as fast as computers: we have full scale computers (and routers, and firewalls, and switches) for that. Embedded is about solving problems more physical in nature, as you are physically closer to reality in nearly all aspects. -------- An MCU + FPGA project could implement... say... the VFIR IrDA (Infrared) protocol at 16Mbit. Traditional IrDA is widely supported at SIR and MIR levels (upto 1.152MBit or so). Anything faster and the equipment has basically been lost to the 1990s (and never was very popular anyway). IrDA I'd explain as a remote-controller on steroids. Its infrared based (like TV Remote Controllers), so you need to line up both devices and have them looking at each other. Infrared can reliably travel about 3 meters over the open air in a variety of conditions. IrDA allows for bidirectional communications. Its a truly wireless protocol, albeit one that requires significant alignment to function correctly. But ~3 meters is good range and practical for many applications. Nominally, you could use an entire MCU to handle the encoding / decoding of these light-pulses. However, that's a bit redundant. Its far more cost efficient to dedicate a few LUTs in an FPGA to the task. Yes, the MCU is needed for the final application-level / OSI layer 4/5/6/7 aspects of IrDA protocol. But the lowest PHY and MAC levels of the protocol can and (probably) should be a small section of FPGA. Upgrading from standard MCU 1MBit to 16MBit would be a 1600% improvement to communications compared to what's readily available with commercial-off-the-shelf solutions. If you've determined that IR Communications is good for whatever purpose you're using, maybe the 1600% improvement is going to be useful. ------------ EDIT: The "physicality" of this is because photodiodes react very quickly to light pulses. And an expensive enough transistor can amplify that at the ~100MHz speeds needed to run VFIR (at least in theory. I've never done this). The FPGA (or MCU if you go that route...) just needs to clock at 100MHz or so, and interpret the start-of-frame and end-of-frame signals, while also interpreting a few other low-level details. Overall, this turns the sequence of light pulses into bits-and-bytes for higher-level processing (which code can and should handle).
- rkangel 2y ago
  > Embedded projects are never about doing things as fast as computers: we have full scale computers (and routers, and firewalls, and switches) for that. That's a bit of an overly broad statement. I have several times at work done projects that use FPGAs to do things faster than a computer can do, e.g. some specific processing of a full 10Gbps UDP stream, which is much easier to get 100% reliable without packet drop in digital logic than it is in software land. The FPGA+CPU combo allows you to do a LOT of things. I tend to use just a straight Zynq so I already have my memory buses wired up from processing system to digital logic, but this is an interesting architecture.

real quite high level sorry, most of your embedded projects going forward are MCU+fpga to do what? I thought a custom router but 284mbps isn't nearly fast for a network.

UncleOxidant 2y ago

It's a good question. A lot of FPGA projects I see (including some real life products I've looked into recently) don't really need an FPGA. One I was asked to evaluate recently could easily have been done with a microcontroller with PWM outputs. The frequencies involved were well under 40MHz. Yes, there were a couple of multiplications going on in the FPGA, but there those could've been easily handled by a micorcontroller. An RP2040 would've sufficed instead of what they had - a microcontroller + an FPGA.

azonenberg 2y ago
The projects in question include things like a 48 port gigabit Ethernet switch with packet datapath in the FPGA, and dual 10/25G SFP28 uplinks. You're not doing that on a MCU. Also higher end oscilloscope work (e.g. 10 Gsps 12-bit JESD204B) But a STM32 is more than sufficient for the management interface on both.
rvense 2y ago
I think a lot of people don't fully appreciate how fast a modern "microcontroller" is. That 'H735 is probably faster than every computer I had up to and including the iBook G4 I until early 2009.
- buescher 2y ago
  I keep running into that also. It's like the common mental model of a microcontroller froze around Y2K as a sort of headless VIC-20. I had an FAE, and a good one, from a major supplier tell me "you can't implement a filter" on a low-end micro that was roughly as powerful as an early nineties DSP.
  - rvense 2y ago
    Cortex-Ms, man. A lot of 'em you just give 3.3V and a couple of bypass caps, and GCC will use the single-cycle hardware MAC (for M4 and above) if you just write the straight-forward C code and you can put it on there in 600ms with DFU. I'm a hobbyist, not an embedded wizard, but it really seems *pretty* good compared to what I understand about the old days. (Like I like retro stuff and during COVID I bought an old DSP56k dev board with a book about the assembly language but oh boy, oh dear)
    - buescher 2y ago
      They're amazing. And - you can run a PC emulator on an ESP32. Sure, you need the fancy ram. OK. And then people will tell me an ESP32 can't do things that people definitely were doing on bare-bones PCs in the eighties.
15155 2y ago
Zynq 7010s are $2.50 and are a hell of a lot more chip than an RP2040. If you already have the design (or copy one of the 50 available), it's a good option when you don't want to fight the chip. PIO has extraordinarily sloppy timing (skew in all categories) compared to the cheapest and smallest FPGAs.
- azonenberg 2y ago
  Where are you getting them for $2.50?? The XC7Z010-1CLG225C is $74.83 at Digikey in qty 1. Checking sketchier places Win-Source has the CLG400 package for $22.20 and even the cheapest aliexpress seller wants $4.84 for something marked as a 7Z010 that may or may not be legit. Also "fight the chip" is pretty much the definition of what I did last time I did a zynq project. Just give me a plain FPGA and MCU with no wizards or GUIs or automatic code generation.
  - 15155 2y ago
    https://www.aliexpress.us/item/3256803970893483.html https://www.aliexpress.us/item/3256803970893483.html I've ordered trays (and they send the OEM tray) - unique barcodes, legit. > Just give me a plain FPGA and MCU with no wizards or GUIs or automatic code generation. You can pretty much cut out all of their tools and get a pure Yocto/Vivado TCL build for the bitstream for the 7 series Zynqs. Very low touch. Their IO planner (in the Vivado IP integrator) is somewhat necessary for complex peripheral scenarios and is one of the few things I ever use Xilinx GUI applications for anymore.
    - anyfoo 2y ago
      I don’t even find Vivado that bad, but maybe I have Stockholm syndrome. Or maybe it’s because I’m forced to use Intel Quartus right now and wish it was Vivado every time.
    - scottapotamas 2y ago
      I was interested to see, or at least what state they're in so I grabbed a couple. Might try to compare them against some genuine ones with CT and destructive inspection. On the chance they're half reasonable, thanks for the link.

azonenberg 2y ago

The intent is for the high performance datapath to live entirely in FPGA (and the project you're probably thinking of is switching, not routing). The MCU is for control plane only. Several hundred Mbps between the control and data plane is more than enough for a SSH management CLI and poking registers on the FPGA to move a port to a different VLAN in response to a CLI command or add an ACL rule or something.

deleted 2y ago

[deleted]

dragontamer 2y ago

Embedded projects are never about doing things as fast as computers: we have full scale computers (and routers, and firewalls, and switches) for that. Embedded is about solving problems more physical in nature, as you are physically closer to reality in nearly all aspects. -------- An MCU + FPGA project could implement... say... the VFIR IrDA (Infrared) protocol at 16Mbit. Traditional IrDA is widely supported at SIR and MIR levels (upto 1.152MBit or so). Anything faster and the equipment has basically been lost to the 1990s (and never was very popular anyway). IrDA I'd explain as a remote-controller on steroids. Its infrared based (like TV Remote Controllers), so you need to line up both devices and have them looking at each other. Infrared can reliably travel about 3 meters over the open air in a variety of conditions. IrDA allows for bidirectional communications. Its a truly wireless protocol, albeit one that requires significant alignment to function correctly. But ~3 meters is good range and practical for many applications. Nominally, you could use an entire MCU to handle the encoding / decoding of these light-pulses. However, that's a bit redundant. Its far more cost efficient to dedicate a few LUTs in an FPGA to the task. Yes, the MCU is needed for the final application-level / OSI layer 4/5/6/7 aspects of IrDA protocol. But the lowest PHY and MAC levels of the protocol can and (probably) should be a small section of FPGA. Upgrading from standard MCU 1MBit to 16MBit would be a 1600% improvement to communications compared to what's readily available with commercial-off-the-shelf solutions. If you've determined that IR Communications is good for whatever purpose you're using, maybe the 1600% improvement is going to be useful. ------------ EDIT: The "physicality" of this is because photodiodes react very quickly to light pulses. And an expensive enough transistor can amplify that at the ~100MHz speeds needed to run VFIR (at least in theory. I've never done this). The FPGA (or MCU if you go that route...) just needs to clock at 100MHz or so, and interpret the start-of-frame and end-of-frame signals, while also interpreting a few other low-level details. Overall, this turns the sequence of light pulses into bits-and-bytes for higher-level processing (which code can and should handle).

rkangel 2y ago
> Embedded projects are never about doing things as fast as computers: we have full scale computers (and routers, and firewalls, and switches) for that. That's a bit of an overly broad statement. I have several times at work done projects that use FPGAs to do things faster than a computer can do, e.g. some specific processing of a full 10Gbps UDP stream, which is much easier to get 100% reliable without packet drop in digital logic than it is in software land. The FPGA+CPU combo allows you to do a LOT of things. I tend to use just a straight Zynq so I already have my memory buses wired up from processing system to digital logic, but this is an interesting architecture.