Controlling sd card access between MSD driver and app

MIOS programming (C)
1

Hi,

I’m using the mass storage driver similar to the example msd example, so that files on the sd card may be accessed at any time simply by plugging in a computer host via usb.

Is it possible to (I assume a semiphore is required) simultaneously access files by my mios32 application? I’m about to experiment using FILE_ functions <file.h> for file i/o.

I thought I’d ask the question. I’m kind of thinking that the app will need a switch to control which part has sd card file access enabled external_host<->app.

It would be nice if they could both have access to files any time.

thx.

2

Unfortunately semaphores won’t work, as the MSD driver handles SD Card accesses from an interrupt service routine.

Semaphores can only be used for FreeRTOS tasks.

I don’t see a solution without overworking the USB and MSD driver.

Best Regards, Thorsten.

3

Thanks TK,

I’ll use a pushbutton toggle with LED to switch between MSD (when USB is connected to a host) and internal sd card usage.

4

Alternatively MSD mode could be enabled via the MIOS Terminal.

I’ve added a “msd on” command to all major applications meanwhile, see http://svnmios.midibox.org/filedetails.php?repname=svn.mios32&path=%2Ftrunk%2Fapps%2Fcontrollers%2Fmidio128_v3%2Fsrc%2Fterminal.c as an example (search for “msd”)

Best Regards, Thorsten.

5

Ive implemented this in my program from your code,TK.

The problem I’ve found with this, is when I type “msd on”, I can’t then type “msd off” (or anything) because the USB midi is off.

If I use MIOS Studio through GM5 on the PC ( and init with MIOS32_MIDI_DebugPortSet(UART0):wink: I have control as expected.

http://discourse.midibox.org/t/topic/16137

I think I heard that this is not a limitation with Mac (MIDI + COM +MSD at the same time)?

6

Ca. two years ago, where I tried to combine MIDI+COM, it worked under MacOS, but caused a blue screen under Windows.

Meanwhile this combination is not working under MacOS anymore, I’m not sure why but haven’t spent much debugging effort for this topic since this is a very exotic usecase anyhow.

I don’t think that a MIDI+MSD combination will work in parallel, especially because it seems that Windows can only assign a single driver to a USB port.

Best Regards, Thorsten.

7

I think the answer for me at least is to implement a “msd on nn” where nn is number of minutes after which the core reverts back to USB midi.

This way I can edit a config or transfer a file etc, but then regain control over the core via USB midi!