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, jonsm...@gmail.com <jonsm...@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, jonsm...@gmail.com <jonsm...@gmail.com> > wrote: > >> >> >> >> On Tue, Aug 19, 2014 at 3:48 PM, Álvaro Fernández Rojas < >> nolt...@gmail.com> wrote: >> >>> El 19/08/2014 21:43, jonsm...@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 >> jonsm...@gmail.com >> > > > > -- > Jon Smirl > jonsm...@gmail.com > -- Jon Smirl jonsm...@gmail.com
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