topic Re: IMX6SX USB: how to enable/disable internal 1.5K pullup for USB D+ line? in i.MX Processors https://community.nxp.com/t5/i-MX-Processors/IMX6SX-USB-how-to-enable-disable-internal-1-5K-pullup-for-USB-D/m-p/994847#M147635 <HTML><HEAD></HEAD><BODY><P><SPAN>According to the Reference Manual 67.2.5.4 Switchable 1.5K</SPAN>Ω<SPAN> USB_DP Pullup Resistor</SPAN></P><P><SPAN>This product contains a switchable 1.5 K</SPAN>Ω<SPAN> pullup resistor on the USB_n_DP signal. This resistor is switched on to indicate to the host/hub controller that a full-speed-capable device is on the USB cable, powered on, and ready. This resistor is switched off at power-on reset so the host does not recognize a USB device until the processor software enables the announcement of a full-speed device.</SPAN></P><P><SPAN>&nbsp;</SPAN></P><P><SPAN>&nbsp;</SPAN><span class="lia-inline-image-display-wrapper" image-alt="pastedImage_6.png"><img src="https://community.nxp.com/t5/image/serverpage/image-id/94354i3FF200437D67CF57/image-size/large?v=v2&amp;px=999" role="button" title="pastedImage_6.png" alt="pastedImage_6.png" /></span></P><P></P><P><span class="lia-inline-image-display-wrapper" image-alt="pastedImage_7.png"><img src="https://community.nxp.com/t5/image/serverpage/image-id/94386i1DCD70E63E57F957/image-size/large?v=v2&amp;px=999" role="button" title="pastedImage_7.png" alt="pastedImage_7.png" /></span></P><P></P><P style="text-indent: 21.0pt;"><SPAN>However, we do not recommend that you manually change this configuration, because the USB driver will control it.</SPAN></P></BODY></HTML> Sun, 17 Nov 2019 16:49:08 GMT jimmychan 2019-11-17T16:49:08Z IMX6SX USB: how to enable/disable internal 1.5K pullup for USB D+ line? https://community.nxp.com/t5/i-MX-Processors/IMX6SX-USB-how-to-enable-disable-internal-1-5K-pullup-for-USB-D/m-p/994846#M147634 <HTML><HEAD></HEAD><BODY><DIV>I'm using USBOTG2 in peripheral mode. After loading the USB gadget serial driver(g_serial.ko), the D+ line is automatically pulled HIGH, even though it is not connected to a host yet. However, I don't want the D+ line to be pulled up if it's not connected to the host. Is it possible to control this D+ line?</DIV><DIV>I found the following information online. Is this "<SPAN style="color: #ff0000;">firmware control</SPAN>" supported by IMX6SX? Thanks.</DIV><DIV></DIV><DIV><A href="https://www.beyondlogic.org/usbnutshell/usb2.shtml">https://www.beyondlogic.org/usbnutshell/usb2.shtml</A></DIV><DIV><SPAN style="font-size: 22px;"><STRONG>Speed Identification</STRONG></SPAN></DIV><DIV><SPAN style="display: inline !important; float: none; background-color: transparent; color: #333333; font-family: Arial,helvetica,sans-serif; font-size: 12.8px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; visibility: visible; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;">A USB device must indicate its speed by pulling either the D+ or D- line high to 3.3 volts. A full speed device, pictured below will use a pull up resistor attached to D+ to specify itself as a full speed device. These pull up resistors at the device end will also be used by the host or hub to detect the presence of a device connected to its port. Without a pull up resistor, USB assumes there is nothing connected to the bus. <SPAN style="color: #ff0000;">Some devices have this resistor built into its silicon, which can be turned on and off under firmware control</SPAN>, others require an external resistor. </SPAN></DIV></BODY></HTML> Fri, 15 Nov 2019 08:30:32 GMT https://community.nxp.com/t5/i-MX-Processors/IMX6SX-USB-how-to-enable-disable-internal-1-5K-pullup-for-USB-D/m-p/994846#M147634 liushuo 2019-11-15T08:30:32Z Re: IMX6SX USB: how to enable/disable internal 1.5K pullup for USB D+ line? https://community.nxp.com/t5/i-MX-Processors/IMX6SX-USB-how-to-enable-disable-internal-1-5K-pullup-for-USB-D/m-p/994847#M147635 <HTML><HEAD></HEAD><BODY><P><SPAN>According to the Reference Manual 67.2.5.4 Switchable 1.5K</SPAN>Ω<SPAN> USB_DP Pullup Resistor</SPAN></P><P><SPAN>This product contains a switchable 1.5 K</SPAN>Ω<SPAN> pullup resistor on the USB_n_DP signal. This resistor is switched on to indicate to the host/hub controller that a full-speed-capable device is on the USB cable, powered on, and ready. This resistor is switched off at power-on reset so the host does not recognize a USB device until the processor software enables the announcement of a full-speed device.</SPAN></P><P><SPAN>&nbsp;</SPAN></P><P><SPAN>&nbsp;</SPAN><span class="lia-inline-image-display-wrapper" image-alt="pastedImage_6.png"><img src="https://community.nxp.com/t5/image/serverpage/image-id/94354i3FF200437D67CF57/image-size/large?v=v2&amp;px=999" role="button" title="pastedImage_6.png" alt="pastedImage_6.png" /></span></P><P></P><P><span class="lia-inline-image-display-wrapper" image-alt="pastedImage_7.png"><img src="https://community.nxp.com/t5/image/serverpage/image-id/94386i1DCD70E63E57F957/image-size/large?v=v2&amp;px=999" role="button" title="pastedImage_7.png" alt="pastedImage_7.png" /></span></P><P></P><P style="text-indent: 21.0pt;"><SPAN>However, we do not recommend that you manually change this configuration, because the USB driver will control it.</SPAN></P></BODY></HTML> Sun, 17 Nov 2019 16:49:08 GMT https://community.nxp.com/t5/i-MX-Processors/IMX6SX-USB-how-to-enable-disable-internal-1-5K-pullup-for-USB-D/m-p/994847#M147635 jimmychan 2019-11-17T16:49:08Z Re: IMX6SX USB: how to enable/disable internal 1.5K pullup for USB D+ line? https://community.nxp.com/t5/i-MX-Processors/IMX6SX-USB-how-to-enable-disable-internal-1-5K-pullup-for-USB-D/m-p/994848#M147636 <HTML><HEAD></HEAD><BODY><P>Thanks for your answer!</P></BODY></HTML> Mon, 18 Nov 2019 02:07:24 GMT https://community.nxp.com/t5/i-MX-Processors/IMX6SX-USB-how-to-enable-disable-internal-1-5K-pullup-for-USB-D/m-p/994848#M147636 liushuo 2019-11-18T02:07:24Z