4 Replies Latest reply on Mar 19, 2014 6:56 AM by user_14586677

    Problem setting up UART cable

    matthew.marron

       Hi,

      I'm trying to use an FTDI TTL-RS232-3v3 cable with a PSoC1 chip - CY8C27443.

      I'm having trouble defining the input and output pins for the cable. My board is set to be powered externally and regulated at 3.3V (using the Eval1 board). The cable says it is rated at 3.3V for all the signals (RTS/CTS/Tx/Rx). There is an extra pin on there for 5V output from the cable (coming from USB), I have left that disconnected.

      I have set RTS and Tx (which are the board's CTS and Rx respectively) to be HIgh Z pins. However, it seems as though when these pins are both connected to port 2, the board is being powered. When the cable is connected, measuring the board's Vcc to GND gives ~1.78V. The pins on the cable read ~2.57V (between either two of the input pins and ground).

      Why is this happening? Do I have to set up some BJTs or something and, instead, pull the cable's input pins to its ground pin (externally from the board)? I'm really confused..

         

       

         

      Thanks,
      Matt