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

[brent239955_st]

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)  ?

[Tesla DeLorean]

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

[brent239955_st]

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]

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.

[raullette]

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?