2018-03-13 02:00 AM
Hi,
I was wondering if SDMMC can drive more than 1 SD card at a time.
I understand that the cube or the SDMMC functions are not involved here.
I also noticed that FATFS_LinkDriver() use a variable called VOLUMES which is the number of logical drives that can be used.
So my questions are :
Do i have to simply change the variable VOLUMES from 1 to 2 ?Can i do such a thing? using two sd card on the same SDMMC wires ?
and before you ask, i have a working project using SDMMC 1 bit wide bus !
Thanks in advance for all your answers!2018-06-18 10:10 AM
The STM32F769I-EVAL and F779I-EVAL has two microSD sockets, and support two independent SDMMC peripherals.
This kind of adapter permits the use of two different kinds of cards, but only one at a time.
>>Do i have to simply change the variable VOLUMES from 1 to 2 ?
For FATFS to hold state for two cards you'd need to have settings, buffers and structures set up to accommodate that.
>>Can i do such a thing? using two sd card on the same SDMMC wires ?
It's complicated, you'd likely need buffer/transceivers on the socket side, and mutual exclusion and serialization on the software side.
The F76x and F77x parts do support two independent SDMMC peripherals. The H7 parts support a transceiver.
ST has this part
http://www.st.com/en/interfaces-and-transceivers/st6g3244me.html
You might be able to use one of the common TI 8-way automatic transceivers. Something like this might be viable, I'd have concerns about bandwidth and skewing.
http://www.ti.com/lit/ds/symlink/txb0108.pdf