5 Replies Latest reply on Dec 23, 2015 3:02 AM by kadali.haneesh

    CY7C65213 D- voltage level reads 1V instead of 0V




      I am new to CY7C65213 USB-to-UART bridge controller chip.


      I am using it to program my NXP Microcontroller through PC's USB port.


      CY7C65213 connects to PC through USB connector.


      The output of CY7C65213 connects to UART of NXP Microcontroller.


      When using this setup, my Ubuntu OS was not able to detect the Cypress device as COM port, when checked using lsusb command.


      Earlier to this, I made sure the Driver is properly installed by connecting a working CY7C65213 module. Attached is the snapshot of proof that Driver is ok.


      The only difference between the working ckt and non-working ckt is - I have used different supply voltages for VCC and VCCIO pins.


      VCC is connected to VBUS of USB input.


      VCCIO is fed by 3.3V (generated using on-board LDO). The reason for this is, the MCU which is connected to the CYPRESS chip operates at 3.3V.


      I followed the application circuit given in "AN85514: Designing a USB-to-RS232 Solution Using Cypress's USB-to-UART LP Bridge Controller" - "Figure 5. Cypress's USB-to-UART Bridge Interface with MCU (Mixed-Powered Design)"


      When I measured the voltage levels at D+ and D-, I observed


      D+ = 3.3V


      D- = ~1V


      I know that in order for the communication to take place, the differential voltage between D+ and D- should be atleast 3V.


      In that case, D- should have been 0V or atleast close to 0V. But why it reads 1V ? Could this be the reason for the issue ?




      Note: In working module, I have connected both VCC and VCCIO to common 5V VBUS.


      Any help would be appreciated.




      Thanks and regards,