Compiler/STARTERWARE-SITARA: Runtime Read/ Write from BBB to USB/SD card using Ti-RTOS

Dear Frank,

Thanks a lot for your guidance. I highly appreciate your help.

My response to your comments below:

"I'm not clear on what you want to do. It appears you want to use the BBB as a USB Mass Storage Class device connected to a Host PC."
 
Let's say, instead of writing a value to DDR memory as indicated in the code below, I want to write the value of a register to the external drive (USB/ SD Card). 

@*****************************************************************************
@ This API writes to DDR memory
@*****************************************************************************
mem_pattern:
movs r3, r0 @offset memory
movs r0, #0x80000000 @ max address of memory
ldr r0, [r0] @
mov r1, #1 @
mov r2, #2 @
push {r1} @

loop:

@ "Move Not" should fill register with 1s
mvn r1, #0 @
push {r1} @
subs r3, #1 @
bne loop @

ret:
BX lr @ return to c_function

.end

Thanks for the suggestion of the documents to be reviewed. I will go through them asap.

I look forward to your reply.
 
Mahmud

Hi Mahmud,

Mahmud Reaz said:

Let's say, instead of writing a value to DDR memory as indicated in the code below, I want to write the value of a register to the external drive (USB/ SD Card). 

Ok, so you want the AM437x to act as a USB MSC Host?

Please look at the following docs: https://software-dl.ti.com/processor-sdk-rtos/esd/docs/06_03_00_106/AM437X/rtos/index_device_drv.html#driver-overview

Do the diagrams in the sections "USB device Mass Storage Class" or "USB host Mass Storage Class" represent what you want to accomplish?

Regards,
Frank

Hi Frank,

Thanks for helping me. I am sorry as it appears that I am unable to ask the right question to you and I appreciate your patience with me.

I am not familiar with AM437x evm. I am using Baglebone Black in my project and XDS 110 Debug probe.

Diagrams in the "USB Mass Storage Class" or  "USB host Storage Class" look different than the system I have in my mind. 

My desired chain of events is given below:

1. USB thumb drive will be physically connected to the BBB board.
2. The main program will run from CCS to BBB (A8 Core) using XDS 110 (JTAG connector). Only XDS 110 will be physically connected to my Laptop via USB A port, where CCS is running.
3. I want to open a file inside the USB thumb drive.
4. I will periodically write values from the main function to a file in the USB thumb drive.
5. Then, close and save the file in the USB thumb drive so that I can read it from my Laptop.

I look forward to your opinion on this. 

Also, I went through the example codes in MMCSD_bbbAM335x_DMA_armTestproject project. Although there are functions associated with initialization, read and write command I do not see a function that opens and close a file. 
I look forward to your guidance. Thanks for your time.

Hi Mahmud,

Mahmud Reaz said:

My desired chain of events is given below:

What you've described matches with diagram in "USB host Mass Storage Class", with the AM437x EVM replaced with the BBB. Please correct me if I'm mistaken.

"the USB instance will act as a USB host communicating with a USB device that supports Mass Storage Class function (USB thumb drive or a small USB hard drive)."

Mahmud Reaz said:

Then, close and save the file in the USB thumb drive so that I can read it from my Laptop.

In this case you'd disconnect the USB thumb drive from the EVM, and reconnect it to the PC?

Regards,
Frank

Hi Frank, Thanks for your reply.

(1)  Yes, it matches with USB host Mass Storage Class with AM437xEVM replaced by BBB.

(2)  Yes, in the end, I would disconnect the thumb drive from BBB and reconnect it to PC.

Do you have any example code I can append to my existing code to accomplish the task?

I look forward to your help.

Sincerely,

Mahmud Reaz