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Testing a USB-Serial Bridge Controller Configured as USB-UART with Mac® OS – KBA92549 | Cypress Semiconductor

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Testing a USB-Serial Bridge Controller Configured as USB-UART with Mac® OS – KBA92549

Last Updated: July 04, 2014

How do you test a Cypress® USB-Serial Bridge Controller configured as USB-UART with Mac® OS?


A Cypress USB-Serial Bridge Controller configured as Communication Device Class (CDC) UART will automatically bind to the Apple USB CDC driver, which is the CDC driver in Mac OS X.

Follow these steps to test the CDC mode for the Cypress USB-UART LP Bridge on Mac OS:

  1. Connect the USB-Serial Bridge Controller to Mac. The Mac CDC driver (AppleUSBCDC) automatically binds to the device. After the driver successfully binds, a device node is created as /dev/tty.usbmodem.
  2. Install a standard terminal emulator, such as SerialTools, to test the UART functionality of the device. SerialTools is a free application available in the Apple App Store.
  3. Open the SerialTools application. In the Serial Port field, select the Cypress USB-Serial UART device node created in step 1, as shown in Figure 1.

    Figure 1: Connecting the USB-UART Bridge in SerialTools

    serial tools

  4. Configure the UART parameters, such as baud rate, stop bits, data width, and parity.
  5. For simple loopback tests, short the RXD and TXD pins of the USB-Serial device on the board.
  6. Click Connect to start communicating with the device.
  7. Type Cypress in the text field. Because the local echo is always enabled in the SerialTools application, the entered characters will be displayed twice.

    Figure 2: Serial Tools Application Loopback Test Output

    Test output

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