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Comment by TaylorAlexander | Hacker News Reader

Also it’s an Attiny which just isn’t a very good processor. It has 2k of ram. Compare that to my favorite microcontroller, the 32 bit RP2040, which has 264k of ram!

I used to use AVR and sometimes ATTiny processors (all 8 bit) but for the last ten years I’ve exclusively used 32 bit microcontrollers and lately it’s all the RP2040.

I think someone had some fun doing a small layout, but I’d really never recommend anyone use this thing. A Raspberry Pi Pico (which hosts the RP2040) is $5. That one still quite annoyingly uses Micro USB, but there’s plenty of clones that use USB-C which are also $5 each, such as this one: https://a.co/d/0d1foa5f

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>Attiny which just isn’t a very good processor. It has 2k of ram

2k RAM is huge for what most people need do with a microcontroller: read sensor, read push-button/potentiometer, turn on LED, spin motor/servo.

The 20 year old gas heater at my parents place is run by one of those and that has a button/LED user interface and runs PID controllers and safety features. All that in 2k RAM.

It's not enough to run Doom on it it stuff like that but the amount of consumer election with them out there is proof they're not underpowered in any way.

Your commercial heater has code written by a professional engineer who understands the limitations of that system. I’ve been writing embedded systems code for 25 years, and I’m well aware of what can be done by an informed engineer with a limited system.

But this isn’t about running doom. Any beginner that tries to use this system runs the risk of importing a library that carelessly consumes half their ram. If they want to use an I2C sensor with a specialized library, the random person on GitHub who wrote that library might not have optimized their code. If someone sees this board and wants to try it because it looks cute, it’s worth warning them that they’re buying a chip with a 20 year old architecture and extremely limited capabilities.

The flew astronauts to the moon on machines with hand wired magnetic RAM. But if you can get a modern architecture with 264k of RAM for $5, it’s worth warning people that they’re looking at something that is extremely limited compared to other options.

I also have some Twitter followers that seem to love micropython. You can’t even run micropython on attiny because of insufficient RAM. https://forum.micropython.org/viewtopic.php?t=9102

Or let’s say someone wants to run a rainbow pattern on an LED strip. Let’s say they’re using the SK6812 LEDs which are 21 bits per pixel. Let’s also say the rest of their code uses zero bytes of ram and the library is perfectly efficient. Well I hope they don’t try to control a light strip with more than 83 LEDs on it! That would consume all the RAM. If they get a high density LED strip with 244 LEDs per meter, then 83 LEDs represents a 34 centimeter long section of that strip. That’s 13 inches.

People do lots of things with microcontrollers these days, and RAM is cheap and plentiful on modern chips.

You’re not wrong, but the point of this exercise seems to be to produce an arduino uno clone in dip package the same size as the chip on the original arduino.

They aren’t trying to create something better or more capable, they are just making a riff/tribute of what is almost certainly the worlds most popular embedded learning tool.

> someone wants to run a rainbow pattern on an LED strip > I hope they don’t try to control a light strip with more than 83 LEDs on it! That would consume all the RAM

Why do you need to store the pattern in RAM at all?

I would compute the next RGB and shift it out one LED at a time. Maybe you were thinking of using DMA for some async work?

The way these things work(so far as I know) is that for the data to be passed along the chain the gap between transmissions can't be greater than 50 microseconds.

Of course a skilled engineer could write a tight output loop that computes and outputs every value on the fly with a guarantee that the time budget won't be exceeded, but your average Arduino user probably doesn't have the knowledge to do this. So all the control libraries that I know allocate a memory buffer for the whole output stream and let the user update it whenever they want.

That’s right. I’m really thinking of beginners, and as you say all the existing libraries I’m familiar with store the string state in RAM.

> Why do you need to store the pattern in RAM at all?

That’s how the popular libraries do it. Not strictly necessary but the whole point of my warning was to make sure any beginners who saw this understood that this board has serious limitations compared to other options.

Thank you for the clarification.

I don't get why you would need more RAM for more LEDs? Isn't the data shifted out one by one?

My word of warning was for beginners. All these seasoned experts are coming in here to explain to me how they would be perfectly capable of using 2k of ram effectively. But that’s not the case for beginners. The most popular libraries for driving all these LEDs store the state of the full chain on RAM. Not strictly required but it makes working with the LED strips much easier. And most devices have plenty of RAM to support this…

On an attiny14a, with 128B of RAM, I had no problem implementing a 433MHz radio remote decoder, controlling 13 LEDs (via a shift register), a digital pot, a rotary encoder, and one button. With the ability to clear and record new remotes in EPROM.

I definitely didn't use near the whole 128B of RAM. I don't remember how much, because it wasn't ever an issue.

The difficult part was actually the 1024 instructions limit on the FLASH storage. It was written in Rust, which wasn't good with AVR at the time (it got better since then).

Sure. And Pong was implemented in pure logic circuits with no CPU at all. Your comment takes up 530 bytes.

When tools like the RP2040 are available, using an ATTiny should be carefully considered. There’s many better options now, and I think this is worth pointing out to people who might not be aware of its limitations.

You can take a sailing ship across the ocean too but it’s cheaper and faster to fly.

Some people sail for fun. Same with circuit design.

Totally. I absolutely see that the person who designed this little board was having fun. I’m in no way criticizing them for doing that. Actually I think it’s a neat project. I just wanted to add a warning to this thread in case any beginners saw this who are used to working with other modern chips. It might not be obvious to beginners who might not think to check the CPU specs.

There is at least one area where ATtiny still outcompetes RP2040: low power consumption. Even in its lowest-power dormant state, 2040 still burns around 200uA, whereas the ATTiny can sleep on only a handful of uA or less. Even during active use, an ATtiny with low voltage supply and low frequency clock can often do what you need with an order of magnitude or two less power than a 2040. So for a hobbyist project to build a battery-powered device with long lifetime, it’s hard to beat the ATtiny. Otherwise I completely agree!

Yes that’s a good point! I’m designing some RP2040 based LED earrings and the static power consumption is significant for sure. I’ve designed them so that when you place them next to a magnet, an ultra low power consumption magnetic switch completely cuts off battery power, but when they are on and in use that static draw hurts.

264k of RAM is really a lot.

Many C64, ZX Spectrum, Coupé folks would dream of having such an amount of memory available to them, the best they ever got was 128KB.

I think many don't imagine what is possible with such microcontrollers nowadays, and we don't even have to write in Assembly all the time, like back then. These aren't Z80 and 6502 CPUs.

Yes! Modern systems are amazing. And with so much memory available on chips like the RP2040 and ESP32, people are writing their open source libraries to take advantage of that memory. I pity the poor newbie that wants to control a WS2812 LED string with this thing and finds out that just importing the library consumes all the ram (possibly) before the code has even done anything.

What are actually the use cases, is it for hobby or do you use in commercial work?

For the RP2040? It’s absolutely suitable for commercial work with the caveat that it lacks any security features to hide your code from users.

I’m using it on the brushless motor controllers and CAN BUS nodes on our open source farming robot. I’m also using it on some LED controllers for fun, and really anything I want to build. I’m learning about switching power supplies so I’m designing a bidirectional buck/boost controller with discrete components and software control using the RP2040 as the switching controller.

Here’s my motor controller: https://github.com/Twisted-Fields/rp2040-motor-controller

That is really cool! I love that people are actively working on these devices. It’s a field that doesn’t get that much attention.

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