Making my first embedded Linux system

As mentioned by another comment, the flash chosen a 16 Mbit according to Avnet's listing. Storage during component selection is pretty much always in bits, whereas consumers like bytes. That being said, the board should be reworkable to swap the flash.

Other notes: 1. Differential routing was mentioned, but no mention of impedance. It's a short run so it's probably fine (I've run high speed over jumper wires before) but it should be noted. 2. There's merit to it being a very simple board, but an SD card connector may have saved the usability and likely really expanded what you can do with the system. 3. The workaround to load directly into DDR was good thinking. 4. Again understood for simplicity but LDO-ing almost 4V down for a core rail is unideal. I couldn't easily find specs on how much current will be taken on this (or any) rail, but just remember that every milliamp here is 4 milliwatts burned as heat. 5. Good to use a simple SoC like this. Integrating DDR and QFN show a real reverence for the challenges one can run into with modern LP5 and BGA parts. Really don't want that so early in the education.

Overall good article, and good work

Welcome to the world of embedded! :)

As for the SPI flash size: they are almost always given in Mbit, so 16Mbit is 2MB hence the confusion if I were to guess. You would be looking for a 128Mbit one to get 16MB.

Nice work and keep on tinkering!

Having used a ton of vendor Linux BSPs over the years, I can say that often they’re not trying to lock you in to a particular approach when they describe how to EG blink an led. Rather they’re demonstrating that it can be done somehow. Every vendor expects you to take their demo code, evaluate it, and make decisions on your own to get to a working system. I’ve seen a lot of employers get into trouble over the years by shipping the vendor’s code unmodified. Even for LED blinking I might use the vendor’s code as a jumping off point and use the LED subsystem to implement different blink rates. But if I’m using EG a TI AM3359 I might want to go the direct register route instead of the LED is used by the real time coprocessor instead in my application. Usually more hands-on distributors like Arrow have Application Support Engineers who can advise for a particular board so you’re not stuck crawling vendor message boards for advice.

For the curious - it looks like this uses the Allwinner F1C100S, which is a 533MHz single-core ARMv7 with 32MB of onboard DRAM.

What other parts are out there that are similar to this? It would be fun to play with one that has a little more RAM, and maybe a faster clock rate.

I think your PCB schematic looks great, especially for your first design! It is quite readable :)

I also started with easyEDA for my first few PCB's, it is very intuitive.

"If V = IR means nothing to you" Yes, U = IR means something to me. So I'm first going few steps back...