[HN Gopher] Making my first embedded Linux system
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       Making my first embedded Linux system
        
       Author : sam_bristow
       Score  : 128 points
       Date   : 2024-06-16 06:51 UTC (16 hours ago)
        
 (HTM) web link (popovicu.com)
 (TXT) w3m dump (popovicu.com)
        
       | dimman wrote:
       | 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!
        
       | Neywiny wrote:
       | 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
        
       | lemonlime0x3C33 wrote:
       | 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.
        
       | throwaway173738 wrote:
       | 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.
        
       | nrclark wrote:
       | 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.
        
         | not_the_fda wrote:
         | The F1C200s has 64MB of RAM, but usually these class of
         | processors move to external RAM.
         | 
         | If you are willing to move to external RAM the iMX6 line is a
         | great processor. Up to 1Ghz, eMMC, some have a GPU. Really
         | great Linux support and documentation.
        
         | dragontamer wrote:
         | Microchips SAM9x60D1G is 128MByte / 1Gbit of onboard DRAM on
         | package.
         | 
         | Single core lol ARMv5 because I assume someone out there still
         | wants Jazelle or something? Updated to 600MHz.
         | 
         | More recent SAM9x75 is 800MHz but still ARMv5. So Microchip
         | coming in with all the ARMv5 that the market wants today!
        
         | megous wrote:
         | Rockchip RV1103 1.1GHz/64MiB ram -
         | https://www.aliexpress.com/item/1005006175964407.html
        
       | misiek08 wrote:
       | "If V = IR means nothing to you" Yes, U = IR means something to
       | me. So I'm first going few steps back...
        
         | flumpcakes wrote:
         | What do you mean by this comment?
        
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