[En-Nut-Discussion] SD card perf issues on EIR board

[Mathieu SOULARD]

Hi all,

I'm trying to know why I'm getting performances issues using SD card on my
EIR board.
(file read at about 10Ko/seconds, not enough to feed the audio codec)

Actually the SD card is driven through a bit banging SPI driver.
I read that the MMC cards can work in SPI mode, or in SD BUS mode, which
allow up to 4 data lines instead of only one in SPI mode.
In that mode, data transfert rate is x4 faster.

I checked the schematic of the EIR board and all MMC pins are connected to
GPIO. So I think it would be possible to use it in SD BUS mode with 4 data
lines.

The implementation of a bit banging SD BUS driver seems to be a big work,
and I have some doubts: even 4x faster, I'm afraid I won't reach enough data
rate to feed the codec.

Does someone know a bit banging SD BUS driver which would be portable in
Nut/Os?
Does someone already tried to implement it over Nut/Os?
Does someone already made modifications to improve data rate over SD card ?




Thanks
Regards


Mathieu