STM32F405 HSE timeout is too short to enter DFU mode

[blackberryer]

Recently, I encountered a tricky problem, I used STM32F405VGT6 this IC, but I found that it could not enter DFU mode normally, after repeated troubleshooting, I found that when the chip was USB probed, HSE was detected and did not vibrate, I also saw a similar article on the forum, I noticed that in the article, changing F405 to F429 can enter DFU mode normally.

Further investigation, comparing the difference between the two ICs, it was found that the HSE start-up timeout time of the F405 IC was too short, and the HSE timeout time of the F405 was found from AN2606, and the version of the v3 version was 0.79ms, and the version of the v9 was relatively normal with 96ms

I want a timeout of 0.79ms, how do I do that? Is there any way to start HSE within 0.79ms of bootloder version v3? I hope the official can give an answer, thank you very much

[FBL]

Hi @blackberryer 

Could you please clarify why you specifically need the HSE timeout to be 0.79 ms, knowing that this short timeout may cause failures? The STM32F405 devices with bootloader version 3 indeed have this limitation, but it is generally not recommended due to the risk of unstable startup.

Regarding your question about extending or configuring the HSE startup timeout on the STM32F405 bootloader v3 to improve DFU mode reliability ! This timeout is fixed within the internal bootloader firmware and is not accessible or configurable by users. Could you share more about your use case or why you need to know this detail?

[blackberryer]

I don't want the HSE timeout of 0.79 ms; it's because the chip I am currently using is the V3 version, and the timeout for the V3 version is 0.79 ms. This is too short. For this version, how can I reliably enter the bootloader? I am using the BOOT and RST buttons to enter the bootloader.

I tried adjusting the matching capacitors of the crystal and increasing the Q factor, which occasionally allowed me to enter the bootloader, but it was still not very stable. I want to ask, aside from version V3, you released newer versions because of the instability in entering the bootloader, right?