DLPC350: Enabling USB in firmware wih USB_EN pin floating

Hello Oliver,

Unfortunately we are unable to provide custom firmware. However, I don't know if that would help you or not. The USB_EN is a pin that enable or disables a buffer for USB input. It should be used to assist in enabling or disabling USB communication. See the reference schematic at www.ti.com/.../dlp4500-c350ref and look for the USB_ENZ signal coming from the SN74LVC1G125DBVR part.

If you still need assistance communicating over USB please provide your schematic so I can assist.

Thanks,
Kyle

Hi Kyle,

Thanks for your response. To clarify: in our design the USB_EN pin has been left floating. Should the USB connection still work even with USB_EN floating?

I am not sure if I can release the schematic but I can check.

Thanks,
Oliver.

Hi Oliver,
Yes, I believe that is the case. The enable pin was used to enable a buffer for the USB pin. If you didn't use a buffer you shouldn't need the pin (though you may run into some other issues). If you are unable to release your full schematic it may still help to see just the USB part if you are able.

Thanks,
Kyle

Hi Kyle,

The USB p/n lines from the dlpc350 are connected directly to a USB hub chip (which we know to be functional since it is being used for other things). There are no additional components between the dpc350 and the USB chip. Is there any reason why we would not see the chip over USB?
We have successfully uploaded the firmware provided by TI to the dlpc350 via JTAG and verified that the write was successful.

Cheers,
Oliver.

Hi Oliver,

I will let you know if I find out anything differently (I want to run an idea by a few coworkers) but I believe that is correct. There shouldn't need to be anything special. Have you been able to communicate over I2C or verify the chip has successfully booted in any other way?

Thanks,

Kyle

Hello Oliver,

Here is another simple test you can try. Can you boot up the DLP system with nothing plugged into the USB. Then once the system has fully booted up try plugging in and establishing the USB communication.

Let us know your results!

Best,
~Danny W

Hi Kyle,

Apologies, I thought I had replied to this but apparently not.  We also tried as you suggested but still the device was not recognised.  We have made a redesign with the USB_EN pin connected; i will let you know the results of this.

Thanks,

Oliver.

Hello Oliver,

No worries! Thanks for letting me know. It is important to make sure you have the appropriate pull-up devices as shown on the reference design for proper initialization.

Thanks,
Kyle