[OpenWrt-Devel] [PATCH v2 1/2] ramips: second spi device on rt5350

[jonsmirl at gmail.com]

How to use SPI bitbang on OpenWRT
http://randomcoderdude.wordpress.com/2013/08/15/spi-over-gpio-in-openwrt/


On Tue, Aug 19, 2014 at 4:03 PM, jonsmirl at gmail.com <jonsmirl at gmail.com>
wrote:

> This site has a write up on how SPI mode works.
> http://elm-chan.org/docs/mmc/mmc_e.html
>
>
>
>
> On Tue, Aug 19, 2014 at 3:59 PM, jonsmirl at gmail.com <jonsmirl at gmail.com>
> wrote:
>
>>
>>
>>
>> On Tue, Aug 19, 2014 at 3:48 PM, Álvaro Fernández Rojas <
>> noltari at gmail.com> wrote:
>>
>>> El 19/08/2014 21:43, jonsmirl at gmail.com escribió:
>>> > How is the clock speed wrong?
>>>
>>> The lowest speed the RT5350 SPI controller can achieve is System Clock /
>>> 128.
>>> System Clock = 120MHz
>>> Lowest SPI Clock = 120MHz / 128 = 937.5KHz
>>>
>>> However, the MMC/SD cards need to be initialized at 100-400KHz.
>>>
>>
>> This might work... Put the SPI pins into GPIO mode. Use the kernel
>> bit-bang support for SPI to initialize the card.  Then go back to high
>> speed mode.
>>
>> --
>> Jon Smirl
>> jonsmirl at gmail.com
>>
>
>
>
> --
> Jon Smirl
> jonsmirl at gmail.com
>



-- 
Jon Smirl
jonsmirl at gmail.com
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