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Unable to enter boot loader mode on STM32F103C8T6: Transmit pin remains as input

Question asked by Jim Seymour on Aug 23, 2017
Latest reply on Aug 28, 2017 by Jim Seymour

We're trying to activate boot loader mode on an STM32F103C8T6.We have an outside device drive the BOOT0 pin HIGH before we apply power.  Then, we send the initial 0x7F byte to the STM at 115200 bps, 8 data bits, even parity.


However, the transmit pin from the STM seems to remain as an input.


Can someone confirm that the TXD1 pin from the STM normally goes high when the boot loader is activated?  And if so, at what point in the sequence? (at power up when it sees BOOT0 high? or only after it receives the 0x7F?)