Serial Downloader Mode - Detailed

[Lukas_Frank]

Hi,

Could you explain what does Serial Downloader mode exactly? Which Program Image exactly downloaded to on-chip RAM during Serial Downloader mode? What means ARM core is reset if no activity found on USB OTG? 

There are some informations in RM but I want to know above details.

Thanks and Regards.

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[EdwinHz]

Hi @Lukas_Frank,

In simple terms, Serial Downloader Mode is a mechanism that allows users to boot from a host rather than a flash or other type of program memory. This is a useful development feature, to override the program memory when it is corrupted or faulty, and or testing different software without going to the process of reprogramming the memory. It is often used as a means of regaining debug access as described here.

With respect to your specific inquiries:

1. The image that will be loaded into RAM will be of the host's choosing.
2. The RT will reset because of the watchdog timer when no activity is found on the USB or UART ports, since there is no connection from the host to program via Serial Downloader.

BR,
Edwin.

[Lukas_Frank]

Hi Dear @EdwinHz ,

How can we achieve the details of which boot files loaded by host into the EVK? What kind of content overriden to program memory by host?

I am curious about normally (in internal boot mode) we are programming the EVK or MCU by IDE with our binary or hex files. Then, what is the files loaded into EVK during the serial download mode? 

Thanks and Regards.

[EdwinHz]

Hi @Lukas_Frank,

Serial downloader mode uses the same binary image as internal boot. The main difference between internal boot mode and serial downloader mode is that in the first, the image is programmed into the memory device and executed from there, while in the latter, the image is obtained from a host. See section "Serial Boot (Serial Downloader)" for more information about serial downloader.

BR,
Edwin.

[Lukas_Frank]

Hi Dear @EdwinHz ,

I read the section before this post. But I can't catch the subtle difference and hot point. You said in serial downloader image is obtained from host. In here, host means our PC devices I think. Please correct me if I am wrong.

So, what changes when the image obtained from host? They both are the same image as a result. But we are able to recover card when we select the serial downloader.

Thanks and Regards.

[EdwinHz]

Hi @Lukas_Frank,

1. Yes, the Host is a PC. I apologize for the confusion.

2. The thing about serial download mode, is that it enables communication to the chip using the Serial Download Protocol (described on section "Serial Download Protocol (SDP) " of the RM and here). Like the post that I previously shared mentioned (link), the flashed code can sometimes cause the debugger to loose access to the RT, rendering it unresponsive and unprogrammable. When this is the case, serial downloader mode is used to regain debug access by allowing the RT to turn on and communicate with a host (PC), without executing any code already stored in flash. This allows the PC to erase the flash and therefore regain control of the RT device.

BR,
Edwin.

[Lukas_Frank]

Hi @EdwinHz ,

• Can we say that the Flash Memory is corrupting is such a way that avoids debugger access to the RT when the wrong/miss operational code loaded into Flash even for the once?
• Is there a strict definition of this Flash Memory corruption in technical level or is it a totally undefined action which can not be traced easily? If exist a strict definition of this error maybe I can avoid it in development process.

Thanks and Regards.

[EdwinHz · Accepted solution]

Hi @Lukas_Frank,

• Correct.
• It is usually a non traceable consequence, making it difficult to pinpoint in code. However, other times it can be avoidable with good coding practices.

BR,
Edwin.

[Lukas_Frank]

Dear @EdwinHz,

Thank you for support.

Best Wishes. 

[karltoo54]

gana gato@Serial Downloader Mode" could refer to different contexts, such as a feature or operation mode in various devices or software. Without specific details about the context, it's challenging to provide a detailed explanation. However, I'll cover a couple of possibilities where the term might be relevant:

1. Computer BIOS/UEFI Serial Downloader Mode: Some computers and motherboards have a feature called "Serial Downloader Mode" that allows firmware updates to be performed via a serial connection. This mode is typically used for recovering or updating the BIOS/UEFI firmware when traditional methods (like flashing from a USB drive) are not possible. This is usually an advanced procedure and requires specific tools and instructions from the motherboard manufacturer.