Usefulness of a bootloader

matic · ‎2016-09-06

Posted on September 06, 2016 at 19:35

Hi.

I would really like to understand why bootloader is useful for? I read the document below, but still didn't get the point.

http://www.st.com/content/ccc/resource/technical/document/application_note/b9/9b/16/3a/12/1e/40/0c/CD00167594.pdf/files/CD00167594.pdf/jcr:content/translations/en.CD00167594.pdf

Could anyone please explain in which cases bootloader is useful and briefly describe how to use it. I would be very grateful...

Matic

matic · ‎2016-09-08

Posted on September 08, 2016 at 16:48

Thank you Jack for that extensive explanation.

I don't need bootloader for downloading or updating the firmware.

We lock flash to all of our products (Level 1). Now, I would like to implement a feature, which would write some application statuses, CPU statuses and things like program counter, etc. to flash in case of a hard fault. Despite this probably won't be needed almost never, it would be much easier to find a problem with this information, if we get back this part.

What I am looking for is, how to read flash with protection level 1 in the easiest way. Our part acts like a slave device. Communication protocol to its master depends on a master itself (SPI, BiSS, SSI, UART, PWM). So, it would be convinient, if there would be common way of reading protected flash for all types of slave.

waclawek.jan · ‎2016-09-08

Posted on September 08, 2016 at 16:56

I read

When the read protection Level 1 is set:

â€“ No access (read, erase, program) to Flash memory or backup SRAM can beperformed [...] while booting from [...] system memory bootloader.

as ''you can't read FLASH through bootloader''.

Where's the backdoor, then?

JW

jpeacock23 · ‎2016-09-08

Posted on September 08, 2016 at 19:43

If I understand this, you want to protect flash against readout but allow flash to be read out......

Seems like the simple solution would be to set read protection to level 0.

Jack Peacock

matic · ‎2016-09-08

Posted on September 08, 2016 at 21:53

I would like to protect a program code, but leave the possibility just to read a certain flash page.