4 ms·

I was feeling a bit like the Petunia and thought "Oh no, not again." :-) One of the annoyances of embedded programming can be having the wheel re-invented a zi

I was feeling a bit like the Petunia and thought "Oh no, not again." :-) One of the annoyances of embedded programming can be having the wheel re-invented a zillion times. I was pleased to see that the author was just describing good software architecture that creates portable code on top of an environment specific library. For doing 'bare metal' embedded work in C you need the crt0 which is the weirdly named C startup code that satisfies the assumption the C compiler made when it compiled your code. And a set of primitives to do what the i/o drivers of an operating system would have been doing for you. And voila, your C program runs on 'bare metal.' Another good topic associated with this is setting up hooks to make STDIN and STDOUT work for your particular setup, so that when you type printf() it just automagically works. This will also then introduce you to the concept of a basic input/output system or BIOS which exports those primitives. Then you can take that code in flash/eprom and load a binary compilation into memory and start it and now you've got a monitor or a primitive one application at a time OS like CP/M or DOS. Its a fun road for students who really want to understand computer systems to go down.

marssaxman 1y ago
This was my attempt at a minimal bare-metal C environment: https://github.com/marssaxman/startc https://github.com/marssaxman/startc
- ChuckMcM 1y ago
  That's awesome. Back in the day this was the strong point of eCOS which was a bare metal "platform" for running essentially one application on x86 hardware. The x86 ecosystem has gotten so complicated that being able to do this can get you better performance for an "embedded" app than running on top of Linux or another embedded OS. That translates into your appliance type device using lower cost chips which is a win. When I was playing around with eCos a lot of the digital signage market was using it.
  - guestbest 1y ago
    Does anyone still do it that way?
    - ChuckMcM 1y ago
      With AMD64 style chips? Probably not. Multi-core systems really need a scheduler to get the most out of them so perhaps there are some very specific applications where that would be a win but I cannot think of anything that isn't super specific. For ARM64 chips with a small number of cores, sure that is still a very viable too for appliance type (application specific) applications.
OnACoffeeBreak 1y ago
No BIOS necessary when we're talking about bare metal systems. printf() will just resolve to a low-level UART-based routine that writes to a FIFO to be played out to the UART when it's not busy. Hell, I've seen systems that forego the FIFO and just write to the UART blocking while writing.
- ChuckMcM 1y ago
  I hope nobody was confused into thinking I thought a BIOS was required, I was pointing out the evolution from this to a monitor. I've written some code[1] that runs on the STM32 series that uses the newlib printf(). I created the UART code [2] that is interrupt driven[3] which gives you the fun feature that you can hit ^C and have it reset the program. (useful when your code goes into an expected place :-)). [1] https://github.com/ChuckM/ https://github.com/ChuckM/ [2] https://github.com/ChuckM/nucleo/blob/master/f446re/uart/uart_example.c https://github.com/ChuckM/nucleo/blob/master/f446re/uart/uar... [3] https://github.com/ChuckM/nucleo/blob/master/f446re/common/uart.c https://github.com/ChuckM/nucleo/blob/master/f446re/common/u...
- nonrandomstring 1y ago
  Yup, I recall Atari ST (68000) and BBC Micro (6502) having unbuffered and interrupt access to 6402 UART - which I used to C/ASM to fire MIDI bytes to and from.
LelouBil 1y ago
At my school, we did the following project : https://github.com/lse/k https://github.com/lse/k It is a small kernel, from only a bootloader to running elf files. It has like 10 syscalls if I remember correctly. It is very fun, and really makes you understand the ton of legacy support still in modern x86_64 CPUs and what the os underneath is doing with privilege levels and task switching. I even implemented a small rom for it that has an interactive ocarina from Ocarina of Time.
- pyuser583 1y ago
  What is your school? I thought it was the London School of Economics, but it’s another LSE.
  - LelouBil 1y ago
    It's EPITA, in France. LSE is the System's laboratory of EPITA (https://www.lse.epita.fr/ https://www.lse.epita.fr/)
- ChuckMcM 1y ago
  This is really neat. So many engineers come out of school without ever having had this sort of 'start to finish' level of hands on experience. If you ever want to do systems or systems analysis this kind of thing will really, really help.
- LelouBil 1y ago
  Also, if anyone wants to try it, the whole course is available publicly here (in English) https://k.lse.epita.fr/ https://k.lse.epita.fr/
deleted 1y ago
[deleted]
dusanh 1y ago
This sounds fascinating and absolutely alien to me, a Python dev. Any good books or other sources to learn more you can recommend?
- genewitch 1y ago
  There's always the Minix book!
- pjmlp 1y ago
  You can start here, https://wiki.osdev.org/Expanded_Main_Page https://wiki.osdev.org/Expanded_Main_Page Also regardless of what others say, you can have a go trying to feel how it was to use BASIC in 8 bit computers to do everything their hardware exposed, or even 16 bit systems like MS-DOS, but with Python. Get a ESP32 board, and have a go at it with MicroPython or CircuitPython, https://docs.micropython.org/en/latest/esp32/quickref.html https://docs.micropython.org/en/latest/esp32/quickref.html https://learn.adafruit.com/circuitpython-with-esp32-quick-start/overview https://learn.adafruit.com/circuitpython-with-esp32-quick-st...

marssaxman 1y ago

This was my attempt at a minimal bare-metal C environment: https://github.com/marssaxman/startc https://github.com/marssaxman/startc

ChuckMcM 1y ago
That's awesome. Back in the day this was the strong point of eCOS which was a bare metal "platform" for running essentially one application on x86 hardware. The x86 ecosystem has gotten so complicated that being able to do this can get you better performance for an "embedded" app than running on top of Linux or another embedded OS. That translates into your appliance type device using lower cost chips which is a win. When I was playing around with eCos a lot of the digital signage market was using it.
- guestbest 1y ago
  Does anyone still do it that way?
  - ChuckMcM 1y ago
    With AMD64 style chips? Probably not. Multi-core systems really need a scheduler to get the most out of them so perhaps there are some very specific applications where that would be a win but I cannot think of anything that isn't super specific. For ARM64 chips with a small number of cores, sure that is still a very viable too for appliance type (application specific) applications.

OnACoffeeBreak 1y ago

No BIOS necessary when we're talking about bare metal systems. printf() will just resolve to a low-level UART-based routine that writes to a FIFO to be played out to the UART when it's not busy. Hell, I've seen systems that forego the FIFO and just write to the UART blocking while writing.

ChuckMcM 1y ago
I hope nobody was confused into thinking I thought a BIOS was required, I was pointing out the evolution from this to a monitor. I've written some code[1] that runs on the STM32 series that uses the newlib printf(). I created the UART code [2] that is interrupt driven[3] which gives you the fun feature that you can hit ^C and have it reset the program. (useful when your code goes into an expected place :-)). [1] https://github.com/ChuckM/ https://github.com/ChuckM/ [2] https://github.com/ChuckM/nucleo/blob/master/f446re/uart/uart_example.c https://github.com/ChuckM/nucleo/blob/master/f446re/uart/uar... [3] https://github.com/ChuckM/nucleo/blob/master/f446re/common/uart.c https://github.com/ChuckM/nucleo/blob/master/f446re/common/u...
nonrandomstring 1y ago
Yup, I recall Atari ST (68000) and BBC Micro (6502) having unbuffered and interrupt access to 6402 UART - which I used to C/ASM to fire MIDI bytes to and from.

LelouBil 1y ago

At my school, we did the following project : https://github.com/lse/k https://github.com/lse/k It is a small kernel, from only a bootloader to running elf files. It has like 10 syscalls if I remember correctly. It is very fun, and really makes you understand the ton of legacy support still in modern x86_64 CPUs and what the os underneath is doing with privilege levels and task switching. I even implemented a small rom for it that has an interactive ocarina from Ocarina of Time.

pyuser583 1y ago
What is your school? I thought it was the London School of Economics, but it’s another LSE.
- LelouBil 1y ago
  It's EPITA, in France. LSE is the System's laboratory of EPITA (https://www.lse.epita.fr/ https://www.lse.epita.fr/)
ChuckMcM 1y ago
This is really neat. So many engineers come out of school without ever having had this sort of 'start to finish' level of hands on experience. If you ever want to do systems or systems analysis this kind of thing will really, really help.
LelouBil 1y ago
Also, if anyone wants to try it, the whole course is available publicly here (in English) https://k.lse.epita.fr/ https://k.lse.epita.fr/

deleted 1y ago

[deleted]

dusanh 1y ago

This sounds fascinating and absolutely alien to me, a Python dev. Any good books or other sources to learn more you can recommend?

genewitch 1y ago
There's always the Minix book!
pjmlp 1y ago
You can start here, https://wiki.osdev.org/Expanded_Main_Page https://wiki.osdev.org/Expanded_Main_Page Also regardless of what others say, you can have a go trying to feel how it was to use BASIC in 8 bit computers to do everything their hardware exposed, or even 16 bit systems like MS-DOS, but with Python. Get a ESP32 board, and have a go at it with MicroPython or CircuitPython, https://docs.micropython.org/en/latest/esp32/quickref.html https://docs.micropython.org/en/latest/esp32/quickref.html https://learn.adafruit.com/circuitpython-with-esp32-quick-start/overview https://learn.adafruit.com/circuitpython-with-esp32-quick-st...