2011-03-02 09:02:24     Query regd USB 5V EN line for BF527

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2011-03-02 09:02:24     Query regd USB 5V EN line for BF527

Ashish Gupta (INDIA)

Message: 98593   




I wanted a clarification on the behaviour of the USB 5V enable line when Blackfin is in HOST mode running uclinux with musb driver.


HW platform: TLL6527M


OS : 2010R1-RC5


On our HW platform, blackfin GPIO PG11 is connected the USB 5V enable line of our power subsystem (active high - switches on 5V on the USB_VBUS to power slave devices like USB pendrive when in host mode)


So I mapped the GPIO_PG11 to gpio_vrsel  in the platform file as below:


static struct musb_hdrc_config musb_config = {

.multipoint = 0,

.dyn_fifo = 0,

.soft_con = 1,

.dma  = 1,

.num_eps = 8,

.dma_channels = 8,

.gpio_vrsel = GPIO_PG11,

/* Some custom boards need to be active low, just set it to "0"

* if it is the case.


.gpio_vrsel_active = 1,

.clkin = 24, /* musb CLKIN in MHZ */




I selected the "USB HOST mode" in configuration file. Compilation went fine and then I check out the working by plugging in a USB pendrive. Next I monitored the PG11 line on scope and following is what I found:


Case 1->When connected to pen drive using usb mini type A cable, the PG11 went high, thus enabling the 5V power to the pendrive and I was able to mount the pendrive and access files. So this is good.


Case 2->When no cable connected or usb mini type B cable connected, the PG was low, thus keeping the 5V power switched off during no connection and when connected to a host using cable type B, so this is also good.


Case 3->But when only the cable (usb mini type A) is connected to the Blackfin USB OTG port and not device on the other end, I found a 1 sec pulse on the PG11 line which reapeats after every 3 sec. See attached scope screenshot.


I wanted to confirm if the Case 3 behaviour is "normal" or "acceptable" behaviour of the driver, as per the USB specs. Do the BF527 Ezkits behave the same?










2011-03-02 22:01:54     Re: Query regd USB 5V EN line for BF527

Mike Frysinger (UNITED STATES)

Message: 98610   


for pure hardware questions like this, you'll probably get better luck here:





2011-03-02 23:00:34     Re: Query regd USB 5V EN line for BF527

Sonic Zhang (CHINA)

Message: 98611   


MUSB driver use a timer to validate HOST mode of the USB device, because there is not a ID PIN interrupt available in MUSB IP.  If you insert only the cable, the timer repeats running till you either insert the USB device or remove the cable.