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Intermittant uploads via Serial bootloader

Question asked by clark.roger on Nov 24, 2014
Latest reply on Nov 24, 2014 by clark.roger
First excuse this newbee post, as this question has probably been asked before, but I've not found an answer.

I'm evaluating a several STMF103 based minimum development boards from eBay, and I'm getting a lot of problems putting the boards into Serial Bootloader mode, connecting via STMs windows "demonstration" uploader.

I'm using an external USB to serial  (I've tried several different devices and none was better than the others).

The most problematic board I have uses a STM32F103RCT, and this only seems to enter bootloader mode immediately after power up. And even then only 50% of the time.

I've looked at all the connections and have hard wired Boot0 high and Boot1 low, and replaced the reset switch etc, to no avail.

Is there anything else that could cause the device to not enter serial bootloader mode?
From what I understand, in this mode, even the external clock crystal is not being used, but I'm not sure if my understanding of this is correct.

Is there anything else that causes these devices not to enter bootloader mode?
e.g. values on other pins, possibly clock problems, supply noise problems etc etc ????

Thanks again.

Roger Clark