I'm about to buy a huge amount of USB sticks in order to install a custom OS in them. Do they need a special hardware configuration to make the MBR section suitable for booting? or just by defining it is enough?
Any USB stick can be turned into a bootable USB. They don't need any special configuration. I use universal USB installer software to make a bootable pen drive. You can search on YouTube. It's a 5 minutes process.
Related
My STLINKV2 is not working anymore, not detected by Linux, it failed after the first successful flash. I ordered a new one but it will take 60+ days to arrive. Meanwhile I have heard on Youtube you can program Bluepills directly by connecting cut open USB cable to certain pins and then using a jumper. But I cannot get any precie information on this, is this really possible and how?
You should use the embedded bootloader. You can flash it through several interfaces. Look at AN2606, maybe you can find an already written flasher. Good luck STM32CubeProgrammer handle it.
If you intend to program it through usb, look also at AN3156 all protocols document are referred in chapter 2 of AN2606
THOSE AREN'T CUT OPEN USB CABLES they are USB to serial adapters for arduino's bootloader
They connect them like this:
The problem is that this requires the Arduino STM32 bootloader to be flashed in it.
Another option will be to use STM32CubeProg this program allows you to program your stm over
Serial
SPI
I2C
USB
You'll need to set the BOOT0 and BOOT1 pins to the correct value (HIGH slash LOW) to allow it to go in flash mode during boot.
Here is semi outdated tutorial which tells most of the steps to program a STM using serial. (the Flash Loader Demonstrator is outdated and you should use STM32CubeProg)
I have these related questions:
Does anybody know how an OS gets to know all hardware connected on the motherboard? (I guess this is called "Hardware Enumeration").
How does it determine what kind of hardware is residing at an specific IO address (i.e.: serial or parallel or whatever controller)?
How to code a system module which will do this job? (Assuming no OS loaded yet, just BIOS).
I know BIOS is just a validation and an user friendly interface to configure hardware at boot time with no real use after that for most modern OS's (win, Linux, etc). Besides I know that for the BIOS it should not be difficult to find all hardware because it is specifically tuned by the board manufacturer (who knows everything about it!). But for an OS or an application above BIOS that is a complete different story. Right?
Pre-PCI this was much more difficult, you needed a trick for each product, and even with that it was difficult to figure everything out. With usb and pci you can scan the busses to find a vendor and product id, from that you go into a product specific discovery (like the old days this can be difficult). Sometimes the details for that board are protected by NDA or worse you just dont get to know unless you work there on the right team.
The general approach is either based on detection (usb, pcie, etc vendor/product ids) you load a driver or write a driver for that family of product based on the documentation for that family of product. Since you mentioned BIOS, win, linux that implies X86 or a PC, and that pretty much covers the autodetectable. Beyond that you rely on the user who knows what hardware was installed in the system and a driver that came with it. or in some way you ask them what is installed (the specific printer at the end of a cable or out on the network if not auto detectable is an easy to understand example).
In short you take decades of experience in trying to succeed at this and apply it, and still fail from time to time since you are not in 100% control of all the hardware in the system, there are hundreds of vendors out there each doing their own thing.
BIOS enumerates the pci(e) for an x86 pc, for other platforms the OS might do it. The enumeration includes allocating address space for the device based on pci compliant rules. but within that address space you have to know how to program that specific board from vendor documentation if available.
Sorry my English is not very good.
Responding questions 1 and 2:
During the boot process, only the hardware modules strictly necessary to find and start the OS are loaded.
These hardware modules are: motherboard, hard drive, RAM, graphics card, keyboard, mouse, screen (that is detected by the graphics card), network card, CD / DVD, and a few extra peripherals such as USB units.
Each hardware module you connect to a computer has a controller that is like a small BIOS with all the information of the stored device: manufacturer, device type, protocols, etc
The detection process is very simple: the BIOS has hardcoded all the information about the motherboard, with all communication ports. At startup, the BIOS sends a signal to all system ports asking the questions "Who are you? What are you? How do you function?" and all attached devices answers by sending their information. In this way the computer knows how much RAM you have, if there is present a keyboard or a mouse, which storage devices are available, screen resolution, etc ...
Obviously, this process only works with the basic modules needed to boot the system, and does not work with complex peripherals that require specific drivers: printers, scanners, webcams ... all these complex peripherals are loaded by software once the OS has been charged.
Responding question 3:
If you wants to load a specific module during the boot, you must:
- Create a controller for this module.
- If the peripheral is too complex to load everything from the controller, you must to write all the proccess to control that module directly in the BIOS module, or reprogram the IPL to manage that specific module.
I hope I've helped
Actually, when you turn on your system, the BIOS starts the IPL (Initial program load) from ROM. For check the all connected devices are working good and also check the mandatory devices such as keyboard, CMOS, Hard disk and so on. If it is not success, it gives an error flag to the BIOS. The BIOS shows us the error through video devices.
If it is success, the control of boot is transferred to BIOS for further process.
The above all process are called POST (Power On Self Test).
Now the BIOS have the control. It checks all secondary memory devices for boot loader of the OS. If it hit, the bootloader's memory address is transferred to RAM.
The Ram started to execute the bootloader. Here only the os starts to run.
If the bootloader not hit, the bios shows us the boot failure error.
I hope your doubt clarified...
Articles on this topic from 2012 for earlier RPi hardware extolling the virtues of using an external USB flash drive are now dated.
In 2015, using Raspberry Pi 2 hardware, is there still any advantage to moving the root file system and booting from an external USB flash drive instead of just using the default microSD card?
I'm not sure if the raspberry pi bootloader is even capable of booting from USB, but I could be mistaken (there might be a way to set up an SD card to act as an intermediate step in mounting the OS from USB).
Aside from that, I can't imagine you'll notice much of a speed difference between the micro sd and a USB 2 flash drive (as far as I'm aware, the rpi doesn't have usb 3 hardware). Both will have similar life span.
Other considerations: power consumption (I believe SD has an advantage here, especially since a card will have to be used anyway to boot), quality of either device (you can buy really bad SD cards and USB flash drives alike)
I would be interested in seeing some bench marks if you decide to run any tests to see if there's a difference.
My DriveSpeed benchmark measures speed of large and small file writes and reads, plus random writing and reading. RPi 2 results for SD and USB drives are here.
http://www.roylongbottom.org.uk/Raspberry%20Pi%20Benchmarks.htm#anchor21
For booting, you need to establish which performance feature is more important and it is not just large file data transfer speed. Anyway, it mainly depends on the drive hardware performance characteristics. My system SD card can be out performed by SD cards in a USB card reader.
I was just wondering how the mouse, keyboard works during the boot process. Let us say that I have a USB mouse and a USB keyboard. When I switch on my computer, POST is done just to check whether all the hardware connected to my system are working. But to get a USB hardware working, we need to have a USB driver which ultimately is a process. But if OS is not loaded yet(I mean init and swapper processes), how this process comes into existence? One thing striking my mind is BIOS. But I think, BIOS can't identify the different drivers needed to detect different mouse, keyboards. Please help.
The BIOS is able to enumerate and control a certain subset of USB devices. In particular, mice and keyboards belong to a common class of devices (Human Interface Devices, HID) that are have a common, defined interface and which is fairly to drive. So, the BIOS just has drivers for that class of devices baked in.
Modern BIOSes emulate the PS/2 ports 0x60 and 0x64 using SMM/SMI with a feature often called "USB Legacy Support" (see the EHCI specification for more info.)
When the OS itself loads and initializes the USB controller there is a controller ownership transition from BIOS-owned to OS-owned.
I was wondering if it's possible for the MBR to read data from the USB port?
I'm wanting it to load windows or linux depending on the value it's read from the usb port
You should start with / customise GRUB. As it stands, in the MBR you have very little device support so you'll either have to code your own or try and build on your BIOS's USB device support if that's exposed as an API.
GRUB has built-in OHCI and UHCI USB drivers http://grub.enbug.org/USBSupport . I doubt it'll do exactly what you want out-of-the-box but it'll be easier to customise that rather than start from scratch.
It's highly doubtful that you can fit it into the 512-byte MBR itself, but there's no technical reason it can't be done otherwise - you just need to bootstrap a mini-OS which can read the value, and then act as a chain loader to start the boot loader of the right OS: both GRUB and the Vista bootloader is capable of chain loading to the other, so there's no reason you couldn't do the same.
Having said that, writing said mini-OS could very well prove to be more trouble than it's worth. Customizing an existing bootloader like GRUB is probably your best bet.