[PATCH] bsp/lm4f120: new BSP to support TI LM4F120 XL LaunchPad board

[Karel Gardas]

On 08/29/13 12:01 AM, Eugeniy Meshcheryakov wrote:
> Hello,
>
> 26 серпня 2013 о 19:05 +0200 Karel Gardas написав(-ла):
>>>> +  lm3s69xx_syscon_delay_3x_clocks(524288);
>>> What is this large delay for? Where the number came from?
>>
>> This comes from TI's StellarisWare SysCtlClockSet function. I've
>> used that value since I've thought TI knows what they do (and what
>> they don't correctly describe in spec.) and that's it's probably
>> there for compatibility reason. The comment to this value claims
>> that you need to give used oscillator a time to stabilize and more
>> time is used for faster clock source. Anyway, the value is not
>> needed for my board so if you don't like it I'm free to remove it.
>>
> Well, at that place main oscillator is powered off. And internal
> osicallator will not be used once PLL is running. I think this delay can
> be removed.

OK, will remove it then.

>>> You do the same with SYSCONRCC2_OSCSRC2_MSK. Oring with
>>> SYSCONRCC2_OSCSRC2_MSK cannot be possibly correct, you should use some
>>> constant similar to SYSCONRCC_OSCSRC_IOSC. SYSCONRCC2_OSCSRC2_MSK = 7 in
>>> this field corresponds to 32 kHz oscillator that I dont have available
>>> on my board.
>>
>> Indeed, that's a bug, but on the other hand coincidentally works.
>> Anyway what I'd like to use is:
>>
>>    rcc2 = (rcc2&  ~(SYSCONRCC2_PWRDN2 | SYSCONRCC2_OSCSRC2_MSK))
>>        | SYSCONRCC2_USERCC2 | SYSCONRCC2_OSCSRC2(0x0);
>>
>> as I'd like to use main oscillator. Are you OK with that?
> Yes, that fixes my board.

Cool!

>>
>> BTW, although you claim 32 kHz oscillaros is not available on your
>> board, I've looked into both lm3s6965 and lm3s3749 and both provides
>> 0x7 value for 32.768 kHz external oscillator -- perhaps you've been
>> looking in RCC paragraph instead of RCC2?
> No, all those MCUs support 32kHz oscillators, but to use them one need
> to have external components, that my board does not have.

ACK, so I'll amend the previous patch and resubmit again for your review.

Thanks a lot for your time!
Karel