[SOLVED] Bytewise size flash download with JLinkGDBServer

fparent · Oct 29th 2015, 5:22am

Hello,

I have a board with a STM32F446 cpu and where VDD is 1.8V. The related datasheet says that when VDD is between 1.7V and 2.1V, the flash can only be programmed bytewise. I tried to download an image to flash inside gdb with the "load" command but it does not work, it seems that JLinkGDBServer is using a transfer size greater than a byte. Is there a way to configure GDBServer in order to get a bytewise transfer when I run the "load" command? If not is there another alternative to have bytewise flash downloading?

Thanks,

Best Regards,
Fabien

SEGGER - Niklas · Oct 29th 2015, 10:36am

Hi Fabien,

flash programming is not influenced by J-Link GDBServer, but is done by the J-Link DLL, which downloads a device/flash specific program to RAM, which then programs the flash.
I will check with my colleges if we have any special handling for the STM32F446 in case VDD is 1.7V - 2.1V.

Best regards,
Niklas

SEGGER - Erik · Oct 30th 2015, 9:12am

Hello Fabien,

The SEGGER flash algorithm for the ST STM32F4 series, already takes care of the target voltage. See code below:
if (VTarget > 2700) {
AccessWidth = 4;
} else if (VTarget > 2400) {
AccessWidth = 2;
} else {
AccessWidth = 1;
}
[...]
FLASH->CR = ((AccessWidth >> 1) << 8 );
[...]

No special setup needs to be performed on your side. If VTref is 1.8V, the algorithm will use the x8 transfer size.

Best regards
Erik

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