XR21B1420

For some UARTs, Microsoft certified drivers are available for Windows Operating System and can be downloaded via Windows Update. These drivers and others, including for Linux and other Operating Systems can be found by visiting https://www.exar.com/design-tools/software-drivers Please note Software Driver Use Terms.

Find the product page of the part that you want to get an evaluation board for and click on Parts & Purchasing. Example:

 

Find the icons under Buy Now or Order Samples:

 

Click on the Buy Now icon and see who has stock and click on the Buy button:

 

 

 

If the icons are missing, then contact Customer Support.

USB peripheral devices may operate in bus or self-powered modes. In bus powered mode, the peripheral device is powered by the USB host 5V VBUS power either directly, or for example through a voltage regulator that might provide a regulated 3.3V to the device from the 5V VBUS input. In self-powered mode, power to the peripheral device comes from another source other than the USB host VBUS. For example, power might come from an AC to DC converter.

MaxLinear USB to serial / UART(s), USB hubs and USB to Ethernet devices all comply fully to USB standards and are fully USB compliance tested. One USB compliance test ensures that self-powered peripheral devices do not have “back voltage” when disconnected from the USB host, on either the USB data signals (USBD+ / USBD-) or the VBUS power itself.

All MaxLinear USB UARTs, hubs and USB to Ethernet devices are USB full speed or high-speed devices. As such, they have an internal pull-up on the USBD+ signal to “advertise” their speed rating. The VBUS_SENSE pin on these devices must be connected to VBUS from the host, or upstream device if that is not the host, such that the device “senses” the disconnection from the host or upstream device. The default power mode advertised to the USB host for all USB UARTs and USB to Ethernet devices is bus powered mode. Self-powered mode can be programmed in either the internal OTP memory or external EEPROM for self-powered mode. For MaxLinear hubs, an external pin controls the power mode advertised to the USB host, except the XR22417 which must always be operated in self-powered USB mode.

1. Native drivers: Native drivers may be found in all major OS such as Windows, Linux, and Max OSX. Typically these drivers will be automatically loaded. In some cases, these are basic drivers and may have limitations on advanced device functionality, however. USB HID, Hub and CDC-ACM drivers are examples of native drivers. The CDC-ACM driver be used with our CDC-ACM class USB UARTs, but has limited functionality.

2. MaxLinear custom drivers: MaxLinear custom drivers may be used to support additional functionality in MaxLinear devices. For example, the MaxLinear custom driver for USB UARTs overcomes the limitations of the native CDC-ACM driver. See https://www.exar.com/design-tools/software-drivers for a list of and access to the drivers that we currently have. In some cases, the MaxLinear driver can also be customized, or source code can be provided after executing a Software License Agreement.

Yes: Go to the product page (XR22804 example below), click on the documentation tab on left, click on “Sample USB UART GUI” under Software:

 

The following lines of code must be modified in the xr_usb_serial_hal.c file in the xr_usb_serial_set_flow_mode function at the end of the function:

Change from:

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_flow_addr, flow);

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_gpio_mode_addr, gpio_mode);

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_flow_addr, 0x0);

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_gpio_mode_addr, 0x3);

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_flow_addr, 0x0);

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_gpio_mode_addr, 0xB);

All of MaxLinear / Exar's USB UARTs are CDC class / CDC-ACM compliant, except for XR21B1421 which is an HID class device. This means they can use a native CDC driver. All major OS have native CDC drivers, except Windows prior to Windows 10.

None of the MaxLinear / Exar USB UARTs require their custom driver, however they will have certain limitations when not using it. The native CDC driver is not capable of accessing the internal memory map of any device. As a result, when using the native CDC driver, the device “defaults” to a particular configuration. The main implications of this default configuration are that hardware RTS/CTS flow control is enabled and that other settings / advance settings are not configurable. Some devices, for example the XR21B1411 which has an internal OTP memory, can be programmed to change this default configuration, but the configuration cannot be changed “on the fly”.