UART数据逻辑电平不正确

嘿，大家好。我一直在用UART来处理我的LCD屏幕，在把它添加到我的现场PIC18F4680之前我在台上测试设置。这一切都在工作台上正常工作，我可以使用9600k波特率通过UART传输Tx和Rx数据。我现在已经用UART设置和编码更新了我的实时PIC18F4680，它看起来Rx正确，但是不能传输Tx。我用一个范围检查逻辑级别，我发现了一些非常奇怪的东西。在Tx线上，逻辑电平从5V变为4V。Rx线从3V变为0V，我推测开关电平在2.4V左右，这就是为什么Rx线工作而Tx线不工作。有人知道我会有什么问题吗？只是为了记录它（因为有些人会抱怨）使用；PIC18F4680 C18编译器MPLAB 8.63



      以下为原文

    Hey All.

I have been messing with UART for my LCD Screen and been testing the set-up on the bench before adding it to my live PIC18F4680.  It all worked onbench correctly and I could Tx and Rx data over UART using 9600k Baud Rate.

I have now updated my live PIC18F4680 with the UART set-up and Code and it seem to Rx Corrrectly but couldn't Tx.  I check the logic level using an scope and I have noticed something very strange.  On the Tx Line the logic level is going from 5V and only switching to 4V.  the Rx Line is going from 3V and switching down to 0V and i presume the switch level is around 2.4V and thats why the Rx Line is working and Tx Line isn't.

Does anyone know what I could have this issue?

Just to document it (because some people would moan)
Using;
    PIC18F4680
    C18 Compiler
    MPLAB 8.63
         (Yes I know this is an older version but not updated yet - will be as soon as this project has ended)

Jason