设置UART电缆时出现问题该怎么解决？

嗨，我正在尝试使用一个PSTo1芯片-CY8C2643的FTDI TTL RS23 2-3V3电缆。我很难定义电缆的输入和输出引脚。我的板被设置为外部供电并在3.3V调节（使用EVAL1板）。电缆说，它被额定为3.3V的所有信号（RTS/CTS/TX/RX）。有一个额外的引脚上有5V输出从电缆（来自USB），我已经离开了断开。我已经设置RTS和Tx（这是董事会的CTS和RX分别）是高Z引脚。然而，似乎当这些引脚都连接到端口2时，板正在被供电。当电缆连接，测量板的VCC GND给~ 1.78v。电缆上读~ 2.57v引脚（输入引脚和接地两之间）。为什么会发生这种情况？我必须设置一些晶体管之类的东西，相反，拉电缆的输入引脚的接地引脚（外部董事）？我真的很困惑…
谢谢，Matt



     以下为原文
   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