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
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