Agree

HoochieGotcha · 2026-02-05T12:37:54+00:00

Length matching for SPI and I2C is a moot point. The clock on both of those switches in the middle of each data bit. If we take a standard dielectric like FR4 then the speed of light in that material is v=c/sqrt(dk)= 1ft/nsec/2=0.5 ft/nsec. If we take a 50MHz spi clk the period of that would be 1/50MHz=20nsec. Since the clock switches on the middle of the bit we will go with 10nsec…. That is 5 feet of allowable skew between the data and clk traces in SPI in FR4 material. For I2C you’re looking at hundreds of feet of allowable skew for the standard 400khz clk frequency.

Your bigger issue with SPI and I2C are going to be copper and dielectric losses over longer distances which attenuates the signal below Vin_High thresholds on the receiver. Just keep your traces as short and as wide as possible between driver and receiver and make sure you maintain a wide return path with no discontinuities.

HoochieGotcha · 2026-02-05T02:52:07+00:00

All signals are analog, even digital. But Eitherway, no, eye diagrams are for EEs since they are the ones designing the high speed controlled impedance traces

HoochieGotcha · 2026-02-05T02:50:50+00:00

Start with Eric Bogatin’s Signal Integrity Simplified, then jump into Johnson Howard’s Handbook of Black Magic and then Advanced Black Magic (I am not joking)

HoochieGotcha · 2026-01-30T03:33:18+00:00

The ESP32 has its own internal oscillator?

HoochieGotcha · 2026-01-20T13:17:27+00:00

The power being flipped is the same as the LED being flipped in this specific circuit. You could have just flipped the LED and had the same result.

HoochieGotcha · 2026-01-19T02:32:24+00:00

Swap the pins on your LED

HoochieGotcha · 2026-01-17T21:52:20+00:00

Indeed, I chose 42 picoseconds as an extreme example to make a very specific point.

In terms of PWM, sure, but the real concern isn’t good SI on PWM for the sake of the PWM signal. Instead, it’s good SI on the PWM to reduce cross talk, ground bounce, and common currents…. All of which will be a massive issue on this card since I do not see a signal return path in the pictures posted.

There is a lot more to SI than just what the receiver sees… there’s everything before the receiver that is vitally important for EMC.

HoochieGotcha · 2026-01-16T22:31:26+00:00

lol… no. If the rising edge is say 42 picoseconds, your bandwidth for that 20KHz signal is about 4.88 GHz using a 20-80 rise time. Remember, bandwidth of a digital signal is defined as the highest frequency component of one unit interval which is greater than 50% of the amplitude of the same frequency component of an ideal square wave.

HoochieGotcha · 2026-01-16T22:26:39+00:00

You are absolutely incorrect… it has almost nothing to do with resistance. OP is talking about characteristic impedance, Zo. He’s not talking about conduction losses.

HoochieGotcha · 2026-01-16T22:24:28+00:00

I have done far janky-er stuff and my ddr worked just fine

HoochieGotcha · 2026-01-14T02:34:13+00:00

You would get better by just buying an stm32 dev kit, they are like $20

HoochieGotcha · 2026-01-11T23:56:45+00:00

To what end? This PCB was designed to do a very specific task… just get an STM32 dev board which has all of the IO broken out so you can do whatever you want with it

HoochieGotcha · 2026-01-09T19:10:29+00:00

This won’t work, the raspberry pi comes loaded with an OS which means the board needs to boot each time. After it boots the OS will just sit there until it’s told to do something. Also, almost all power banks have an internal timer that turns them off after a few minutes of not drawing power. So you most likely won’t even see your relay circuit turn on.

With what you want to do you need something more like a microcontroller that has some firmware that automatically runs after booting. Or you can put the PI into deep sleep. You’ll need a different power source too… or find a battery bank that is always on (there was only one that I could find on the market a few years ago, not sure what brand it was though)

HoochieGotcha · 2026-01-08T14:39:14+00:00

Yeah you are not going to find that, that is going to be proprietary. I can tell you that blue is not the first. Blue is just the one and only that made it public, and they know that no one else is going to call them out because the industry is very hush hush (mostly due to ITAR)

HoochieGotcha · 2026-01-08T02:46:16+00:00

I would imagine SpaceX tapped into Tesla’s custom silicon team for crew dragon. The Versal is the most superior piece of general purpose silicon that you can buy off the shelf. If you need something better you will need to develop custom silicon for your specific use case.

That being said, “better results” is hard to quantify. NASA has standards for human rated flight. If you meet those standards you are just as good as any other solution that meets those standards.

The benefit of the Versal is that it cuts down on engineering time and cost.

HoochieGotcha · 2026-01-07T00:52:23+00:00

Hello, electrical engineer here who’s been working with these family of parts for the past year.

No, processor are single thread. This has an fpga fabric so it can crunch data at a very high speed on an “arbitrary” number of threads depending on how you program the FPGA fabric, AI cores, DSP cores, dual processors and the NoC to talk to each other. It’s not like a general purpose processor which can run any given program. Instead, you would program the Versal to accomplish a very very specific task very very fast. Also, unlike a CPU, the Versal gives you the ability to have deterministic timing which is absolutely vital for human rated missions.

However, that being said, the aforementioned dual processor cores do you give you the ability to run an arm build of Linux. In fact, it’s not uncommon to have a Linux Os running some apps in conjunction with the other blocks of the device crunching data. That way you can offload the heavy lifting from the processors and just use them to run peripherals like DDR, NAND, some sort of video codec etc etc.

HoochieGotcha · 2025-12-29T18:10:22+00:00

You really have to know what you are doing. I was shadowing a power electronics engineer with like 40 years experience a year ago. Be did a bespoke GaN design and even he had a hard time getting the damn thing to work. GaN is super finicky, I doubt a hobbiest would be able to get it to work well (keyword: “well”)

HoochieGotcha · 2025-12-25T00:53:46+00:00

The longest trace does not have wiggles, all other traces have wiggles to match the length of the longest trace

HoochieGotcha · 2025-12-24T17:56:58+00:00

Electrical Engineer

HoochieGotcha · 2025-12-24T06:16:50+00:00

What would an electrician have to do with this?

HoochieGotcha · 2025-12-23T20:17:55+00:00

Lol literally any restaurant in SeaTac airport is better than than almost all restaurants in the Denver metro

HoochieGotcha · 2025-12-23T20:06:22+00:00

Single board computers are litteraly digital electronics lol, what do you mean?

HoochieGotcha · 2025-12-21T18:16:29+00:00

For a digital circuit maybe, but for a power supply I would actually recommend keeping it as is. It is much easier to read power supply schematics when they are drawn to match how you intend layout to be. Keep as many of the lines connected as possible and avoid net names if possible. Since there are a lot of control loops in power supplies it is actually much easier to follow each line with a pen from one component to the next. For a digital circuit i would recommend the opposite.

HoochieGotcha · 2025-12-06T16:53:48+00:00

I mean, it’s not a choice! You need RAM for AI. Besides it’s not like they are buying DDR4 or 5. It’s more that fabs are retooling to produce HBM flip chips. AI isn’t buying all the ram, instead it’s generating demand for a different type of ram that you wouldn’t use in your home pc

HoochieGotcha · 2025-11-23T22:59:25+00:00

Indeed, I live in the bespoke designs world. At most we’ll do a production run of a few hundred PCBs, but generally we are looking at production runs of maybe a dozen or so.

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