Sense USB cable connected FRDM-K64F

[giacomopetrini]

Using KSDK 1.1, KDS 2.0

I'm developing a data-logger using the FRDM-K64F

Basically I want a "double" application:

- normal behavior: data logging

- alternate behaviour, when program starts with USB cable connected (to the K64F USB connetor): MSD (so I can read the files saved on the SD card when in data-logging mode)

The data logging works, and I tried the MSD example (and it works).

Now I'm trying to merge the two.

What I wish to do is choose between the two mode at startup: if the USB cable is not conneted -> datalogging, if the USB cable is connected (so the board is connected to a PC) -> MSD.

Some ideas how to do that?

Thanks Regards Giacomo

PS: what throughput I should expect tranfering data from the SD card to a PC (using USB-MSD)?

[ivadorazinova]

Hi giacomopetrini,

you may check power on usb (if is connected to computer or if you need power supply).

Look at the schematic FRDM-K64F http://cache.freescale.com/files/microcontrollers/hardware_tools/schematics/FRDM-K64F_SCH.pdf

Pin 10 on connector J3, page 4. Connect to any pin but through a voltage divider. And the voltage divider connect to any pin and check log 1 or log 0.

You need the voltage divider because the pins are not 5V tolerant and must be here 3.3V maximum.

And with your SD card - you can rewrite the SD - like USB Stack and with the second USB you can send the data away.

I hope it helps.

Iva

[giacomopetrini]

Hello,

thanks for the tip, butI can't use it because on top of the FRDM-K64F there is a "shield" that I designed and it would be difficult to access the P5V_USB pin.

On the other hand the board will be powered by a battery when "on the field": the shiled has a DCDC converter and I read the battery voltage, so I can just read the bat. voltage and if 0 just assume that I'm powering it through the USB cable and switch to MSD mode...

But I hoped that there was some sort of mechanism integrated in the USB module to automatically detect when the device is connected/disconnected to a host.

Regards Giacomo

[ivadorazinova]

Hi giacomopetrini,

voltage you may to read.

Please, which of these examples do you use? dev_msd_disk_frdmk64f_mqx, dev_msd_disk_frdmk64f_bm ?

Many thanks,

Iva

[giacomopetrini]

bare metal.

[ivadorazinova]

Hi,

if you go to disc.c,  you can add the printf if your device is e.g. Attached.

go to void USB_App_Device_Callback(uint8_t event_type, void* val,void* arg)

and add following line 

if(event_type == USB_DEV_EVENT_BUS_RESET)

    {

        g_disk.start_app=FALSE;

    }

    else if(event_type == USB_DEV_EVENT_ENUM_COMPLETE)

    {

        g_disk.start_app=TRUE;

        USB_PRINTF("\n\rAttached\r\n");

    }

and for rejected device (which you must eject by right click on the Removable Disc in Computer)

and add the following line:

switch(event_type)

    {

...

case USB_MSC_START_STOP_EJECT_MEDIA :

            /*  Code to be added by user for starting, stopping or

                ejecting the disk drive. e.g. starting/stopping the motor in

                case of CD/DVD*/

           USB_PRINTF("\n\rRejected\r\n");

            break;

}

now you have an information, when the device was attached and rejected so if you create global variable e.g. unit8_t usb_attached = 0;

and above mentioned fuctions you can change this global variable. In your your logger task you can compare this variable and enable/disable logging.

I hope it helps,

Iva

[giacomopetrini]

OK.

But what I want to do is sense if I need to go to USB mode or normal mode before starting the USB stuff.

I hoped that the USB module in the K60 had some hw flag that is set if a usb cable is connected and reset if the cable is disconneted.

Thanks anyway

Regards Giacomo

PS: it helps anyway, but not for the purpose of my question :smileywink: