Re: [libopenstm32-devel] usart_set_baudrate(...)

[Gareth M. <ga...@bl...>]

On Thu, Mar 10, 2011 at 2:34 AM, Nico von Geyso <Nic...@fu...> wrote:
> I had some problems with the usart_set_baudrate() function and so I took
> a deeper look how it works.
> The baud rade generation for stm32 is described in the section
> "Fractional baud rate generation" in RM0008 Reference manual, Page 747.

If I read it correctly, all the talk in the manual makes it sound fancy and
complicated, but the simple division calculates the correct value.

> For the stm-h107 development the current implementation works fine for
> usart 2,3 but not for usart1.
> Usart1 has a different clock source (PCLK2, 72Mhz) and so you have to
> divide the baud parameter (for usart_set_baudrate(...)) by two to get
> the correct values.
> As it is hard to get the current pclk1 or pclk2 values, wouldn't it be
> better if there is a function like the following:
>
>        void usart_set_baudrate(u32 clock, u32 usart, u32 baud); //set the
> clock manually

I think this is the most obvious way to do it.  I would swap the clock and usart
parameters though.

Regards,
Gareth

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