RTOS: Detecting EPI RAM Presence

Daniel Vamos

Tool/software: TI-RTOS

Hello,

I am looking for any solution to detect the presence of the EPI SDRAM. I put the following code to a device where the RAM is not present and I can not upload any new code into the target. When I hit the debug the CCS says: Error connecting to the target

    uint16_t * start = (uint16_t *)0x60000000;
    uint16_t startVal = start[SDRAM_START_ADDRESS];

EK-TM4C12EXL
TI 18.12.1.LTS
RTOS 2.16.0.08
XDC: 2.32.0.06

over 6 years ago

0 Bob Crosby over 6 years ago

TI__Guru 72500 points

Try initially doing an non-blocking read and use a software timeout loop to check for it to finish. That will prevent the CPU from hanging on a read to non-existent memory.

0 Daniel Vamos over 6 years ago in reply to Bob Crosby

Genius 3950 points

Can you please give me an example about a non blocking read / write? Or a link maybe? This topic is very new for me...

0 Bob Crosby over 6 years ago in reply to Daniel Vamos

TI__Guru 72500 points

There is information about non-blocking reads in section 11.3.2 of the datasheet. However, looking at the EPI drivers in TivaWare should make it even easier. After configuring the EPI, call:

EPINonBlockingReadConfigure();
EPINonBlockingReadStart();

then in a loop try calling EPINonBlockingReadAvail() until it returns a non-zero value. Depending on your interface, it should take very few loops if there is external memory attached. If the loop times out, call EPINonBlockingReadStop() to abort the non-blocking read.

0 Daniel Vamos over 6 years ago in reply to Bob Crosby

Genius 3950 points

Thank you very much for your help.

0 Bob Crosby over 6 years ago in reply to Daniel Vamos

TI__Guru 72500 points

No problem. Sorry I accidently hit the "TI Thinks Resolved" button when I was aiming for the "Reply" button. Let me know if you have any issues implementing this. Also, were you able to do the "Unlock" sequence and recover your part?

0 Daniel Vamos over 6 years ago in reply to Bob Crosby

Genius 3950 points

Not yet. I still dont know how to unlock the launchpad. Do you have any guide?

0 Daniel Vamos over 6 years ago in reply to Bob Crosby

Genius 3950 points

Not yet. I don't know how to unlock the Launchpad. Do you have any guide?

0 Bob Crosby over 6 years ago in reply to Daniel Vamos

TI__Guru 72500 points

See section 5.3 starting on page 20 of this document:
www.ti.com/.../spma075.pdf

0 Daniel Vamos over 6 years ago in reply to Bob Crosby

Genius 3950 points

Thank you very much again for your help!

0 Daniel Vamos over 6 years ago in reply to Bob Crosby

Genius 3950 points

Hello,

Here is my test code:

uint8_t isRAMPresent(){


	uint8_t hasRAM = 0;

    //
    // Ping Device
    //



    EPINonBlockingReadConfigure(EPI0_BASE, 0, EPI_NBCONFIG_SIZE_16, 0);
    EPINonBlockingReadStart(EPI0_BASE, 0, 10);


    uint8_t readAvail = 0;
    uint32_t trials = 4096;
    uint32_t noReads = 0;
    while(trials){


    	if(EPINonBlockingReadAvail(EPI0_BASE) > 0){
    		break;
    	}

    	trials--;
    }


    EPINonBlockingReadStop(EPI0_BASE, 0);

    return hasRAM;

}

There is no RAM peresent in the system and the loop break after the first call.

0 Bob Crosby over 6 years ago in reply to Daniel Vamos

TI__Guru 72500 points

Hi Daniel,
My suggestion was based on an assumption that originally your device was hanging on a read from the EPI. Depending on the configuration of the EPI and the state of the pins when no memory is attached, the read may stall or not. You might be able to make the operation more consistent by configuring the pulls on the appropriate EPI pins. Another approach might be to do a non-blocking write, followed by a non-blocking read to verify there really is SDRAM out there.

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RTOS: Detecting EPI RAM Presence