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brent239955_st
brent239955_st
Associate
August 10, 2016
Question

What USARTs can be used for boot on 64-pin STM32F401RCT6 / STM32F401xB(C)

  • August 10, 2016
  • 4 replies
  • 2467 views
Posted on August 10, 2016 at 16:51

On the 64-pin STM32F401RCT6 there are two USARTs:

  • USART1 on ports PA9 and PA10, pins 42 and 43
  • USART2 on ports PA2 and PA3, pins 16 and 17
I would think that either of these could be used by the bootloader, since the bootloader generally talks about USART1 and USART2.

However, AN2606 specifies that USART2 is on PD5/PD6 (correct for 100-pin package, there is no port D on 64-pin package).

So can USART2 be used for the serial bootloader in a 64-pin STM32F401RCT6 / STM32F401xB(C)  ?

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    4 replies

    Tesla DeLorean
    Tesla DeLorean
    Guru
    August 10, 2016
    Posted on August 10, 2016 at 17:48

    I'd assume only USART1 PA9/PA10 would be viable, and design accordingly.

    You can use whatever USART and pins for your own application implementation

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    brent239955_st
    brent239955_stAuthor
    Associate
    August 10, 2016
    Posted on August 10, 2016 at 19:37

    Thanks for the reply.

    Yes, we have planned for that. It just seemed more likely to me that it was a failure to update documentation from the 100 pin package to the 64 pin package rather than an obtuse decision to limit the number of boot options in the 64-pin package.

    Maybe we will build with some test points to verify that USART is truly not available for serial boot loader.
    Tesla DeLorean
    Tesla DeLorean
    Guru
    August 10, 2016
    Posted on August 10, 2016 at 21:28

    I think it is more a function of having one ROM Boot loader for the die regardless of what package it ends up in. You pick a lower pin count package, your escape options diminish.

    I'd go with the premise that it functions as documented, and PA2/PA3 isn't an option.

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    raullette
    raullette
    Associate
    February 17, 2017
    Posted on February 17, 2017 at 09:41

    Hi,

    Can somebody explain what this line means?

    ''The USART2 uses its remapped pins.''

    I'm using STM32L151CCU6 which doesn't have PD6/7. The bootloader isn't ack'ing when PA2/PA3 is used. Shouldn't the PA2/PA3 be the ''remapped pins'' for this case?

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