Seeeduino XIAO - Arduino Microcontroller - SAMD21 Cortex M0+

Very satisfied with the purchase, all 3 SAMD21 board tested and confirmed working. I will be able to prototype easily with these spare boards

I bought 3 of these a couple years ago to play around with. At the time, it was just because they were cheap and quick to get on Amazon. I quickly fell in love. Though they aren't perfect. Pros: Size. They're tiny. Even 2 years on, most microcontrollers are *at least* 2 to 4 times the size. The small size makes them easy to fit into almost any project. They're literally the size of a postage stamp. I can cover one with my finger. Which brings me to the next pro: I/O. Even at this tiny size, you still have tons of I/O, with support for hardware interrupts, UART, I2C, SPI, and true analog pins with DAC. The big one for me, though, is HID support through the USB type C port. That's a much less common feature than you'd think. If you want to make devices that can talk to other devices as an input device, you need this. Speed. You don't really think that a simple Arduino device needs to be fast, but having a 48mhz processor and 32mb of SRAM to work with open up a LOT of possibilities. Take, for example, my most recent project. I wanted to make a vintage laptop keyboard work with a modern laptop motherboard. But I wanted to do so without damaging the original keyboard. So to interface the two, I needed the Xiao to be able to read the PS/2 protocol that the keyboard was talking in, and give USB HID protocol commands to the computer. Reading the PS/2 protocol takes very precise timing. Your code has to execute within a certain number of microseconds, otherwise the command will fail. Because of the speed of the processor, I could have more code executing in the interrupts while still staying under the threshold. Cons: Storage. While I've never run up against the limit, the Xiao has 256 kB of flash memory. That's not the smallest, but it's certainly not the biggest I've seen on a microcontroller. So I do get a little nervous when I start importing a bunch of libraries. So far, my most involved project, the keyboard that I talked about earlier, only uses about 25% of that storage. And that's importing two different libraries plus my custom code. But if you have a large project that takes many libraries or a whole lot of code, you might run into problems with storage. Bootloader Corruption. I've only had it happen once and it was after hundreds upon hundreds of code uploads. These guys saying they're bricking after 50 uploads have to be doing something wrong. Or maybe it's because they're on Mac hardware, I don't know. But I've had to upload 50 times pretty much everyday I've worked on this project and so far it's not been a problem. But like I said, I did have one of my original three stop responding to USB. So the problem does exist. The device itself still does what the last upload of code told it to do, but I can no longer get it to talk with the Arduino software. And resetting the unit didn't resolve it. So you're mileage may vary.

Very good Stamp sized controller. Best in the series, the ESP32S3 chip is one of the best performers. My application involved an I2S interface to a microphone and four RMT interface outputs to SM2812B leds. Issue #1: The 3.3v regulator on this board has fluctuating output and I need to run my microphone on a separate regulator or I can 'hear' the CPU processing as noise in the microphone. Other arduino boards do not have this issue. The oscilloscope revealed that this chip makes it's power rails rather noisy! Issue #2: Pin 7 (GPIO43) has a part on it that makes the bandwidth poor. This pin isn't usable for high bandwidth control. It's a design choice on their part. Darn good board. Five stars.

I love these little things. Perfect microcontrollers for small spaces. The user should be aware it works 3.3v and not 5v. It also has a USB Type C connection which is different from many microcontrollers like the Arduino Nano. Since it is small, pins are labeled on the underside of the board. I was disappointed that mine did not come with the stickers for the top side marking of the pins. Wish I had the stickers rather than having to refer to a printout to figure out pins.

Absolutely a great value. Not a shill here, but I'm happy to say these are by far some of the best value micro controllers you can be get. I mean, 32 bit and you get 3 for $20 (I'm a prime member and you get them for $19.79 for the 3 pack), what a deal. Now, granted you don't get as many I/O pins, but if you're interested in a controller that truly is tiny and reliable, this is your board. They're also Arduino compatible. You will have to download a new library, but it's not that hard. Go to the Seeeduino website and scroll down really far and it'll show exactly what you need to do to get them working with the Arduino IDE. Some of the instructions may be a little out of date, but they're still useful. In Arduino go to preferences and then boards. You'll need to paste a.link to have the boards added to the IDE. Then search for the "Seeeduino" library. It should say something like Seeeduino boards or something like that. They recently consolidated the library into one. If it's taking long to download, that's the one, you're not doing anything wrong. Then, just plug it in (did I mention it's USB C! yay! Buy a cable or 3 if you don't have one, they're cheap), click verify and upload, it should pop up like a USB stick, do some stuff and then it'll disappear. It'll seem like something went wrong, but it should work. If not, try loading a different example sketch or change a value like making the led flash faster. The default/preloaded code is the blink sketch so change the 1000 to say 100 so you'll be able to tell if it worked. Happy coding!