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您好-寻找方向的大图片是这样的，使用一个平板电脑上的应用程序，我试图改变PIC16F866的占空比输出。我正在使用一个USB到RS232转换器电缆从平板电脑到PIC。我使用的TX/RX和GND从RS232连接器到RX/TX和GND的PIC。所有的应用程序都在向PIC发送数据流，这将改变占空比。应用程序并不期待回应。我已经在TX引脚使用了一个范围，看到什么看起来像一个好信号，所以我相信应用程序工作正常，但它似乎是在一个约6.5伏的水平。我的问题是……我需要用MX23芯片来帮助这个信号吗？我认为它被嵌入到串行转换器中。我知道一个简单的解决方案是升级到一个支持USB的芯片，但是我不能。我目前没有软件，但是如果它有用的话，我可以稍后再安装。任何建议都值得我们欣赏。
以上来自于百度翻译 以下为原文 Hello - Looking for direction The big picture is this, using an app on a tablet I am trying to change the duty cycle output on the PIC16F866. I am using a USB to RS232 converter cable from the tablet to the PIC. I am using the TX/RX and GND from the RS232 connector to the RX/TX and GND of the PIC. All the app is doing is sending a data stream to the pic that will change the duty cycle. The app does not expect a response. I have used a scope on the TX pin and seeing what looks like a good signal so I believe the app is working properly BUT it seems to be at a level of about 6.5 volts. My question is this....do I need the MAX232 chip to help level this signal? I thought it was embedded into the serial converter. I know an easy solution would be to upgrade to a chip that supported USB but I can't. I do not have the software at my current location but if it would be useful I can attach it later. Any suggestions would be appreciated. 
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11个回答
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如果是RS232到USB，是的，你需要一个从RS232到TTL UART的格言。
以上来自于百度翻译 以下为原文 If it is RS232 to USB, yes, you need a MAXim to get from RS232 to TTL-UART |
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是的，来自UB-RS232适配器的信号将从6到6到12／12（RS232电平）。它需要通过PIC UART的收发器（如MAX223）被带到PIC的电压电平来读取它。
以上来自于百度翻译 以下为原文 Yes, the signal coming out of a USB-RS232 adapter is going to be anywhere from 6/-6 to 12/-12 (RS232 Levels). It needs to be brought down to the voltage level of the PIC via a transceiver (like a MAX232) for the PIC UART to read it. |
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首先，这些USB到RS232转换器因低逻辑电平而臭名昭著。官方RS232 HI和Lo是-12V和+12V，但便宜的电缆将几乎不做+-9V。如果这是一个商业项目，你需要使用一个电平转换器来获得RS232电平信号下降到3.3V或5V CPU逻辑电平。如果这是一个家庭项目，请看FTI转换器电缆的Digi键。他们出售5V和3.3V版本，可以直接连接到CPU串行端口。
以上来自于百度翻译 以下为原文 First, these USB to RS232 converters are notorious for low logic levels. Officially RS232 Hi and Lo is -12v and +12v but a cheap cable will barely make +-9v. If this is a commercial project, you need to use a level converter to get the RS232 level signal down to the 3.3v or 5v CPU logic levels. If this is a home project, look on Digi Key for FTDI converter cables. They sell 5v and 3.3v versions that can be connected directly to the CPU serial port. |
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如果你的PIC不具有UART信号的反转，你必须在外部反转它们。MXXXX不仅将信号电平从TTL转换为RS232，而且根据PC RS232端口/USB通信适配器要求转换TX和RX信号。
以上来自于百度翻译 以下为原文 If your PIC doesn't feature the UART signals' inversion you have to invert them externally. The MAXxxx not only converts the signal levels from TTL to RS232 but inverts both TX and RX signals as required by the PC RS232 port/USB-COM adapter. |
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谢谢你的帮助，先生们。它是MAX223。准备好了！
以上来自于百度翻译 以下为原文 Thanks for the help gentlemen. MAX232 it is. All ready ordered one! |
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或者您可以使用AUSB到TTL串行有线电视发布两次。
以上来自于百度翻译 以下为原文 Sorry Posted twice. |
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串行转换器实际上包含两个阶段：第一个USB到TTL串行，然后它使用一个M232风格的缓冲器从TTL转换到RS232电平。这意味着你还需要一个M232风格的缓冲器来从RS232转换回TTL级别。现在你可以看到为什么你也可以选择只使用USB。TTL转换器，正如KATELA所提到的。实际上，USB在PIC端需要很多固件来实现。如果你不需要完整的USB功能，USB到串行转换器是一个更容易的选择。
以上来自于百度翻译 以下为原文 The serial converter actually contains two stages. First USB to TTL serial, then it uses a MAX232 style buffer to convert from TTL to RS232 levels. That means you ALSO need a MAX232 style buffer to convert from RS232 back to TTL levels. Now you can see why you also have the option of using just a USB to TTL converter instead, as mentioned by Katela. Actually no. USB takes a LOT of firmware on the PIC end to implement. If you don't need full USB functionality, a USB to serial converter is a much easier option. |
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HMM，在PICC16F866芯片上的最大VDD额定值为5.5V。TTL输入，65.V似乎是麻烦的。虽然I/O引脚是内部钳位，可能钳位RX和TX到PIC供应轨与信号二极管1N4148。电源电压VDD高于5.5V吗？可能想把它变成
以上来自于百度翻译 以下为原文 Hmmm, the max VDD rating on the PICc16F866 chip is 5.5V. With TTL inputs, 6.5V seems troublesome. Although the I/O pins are internally clamped, maybe clamp RX and TX to the PIC supply rail with signal diodes 1N4148. Is your supply voltage VDD above 5.5V? May want to bring that into spec. john |
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+65V可能不是一个问题，但-65V肯定会是个问题。它可以导致PIC闩锁。
以上来自于百度翻译 以下为原文 The +6.5V may not be an issue, but the -6.5V will certainly be a problem. It can cause the PIC To latch up. |
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你说的是RS232电压。它们不应该连接到PIC。你可以使用一个M232风格的缓冲器，它将RS232电压转换成TTL电压，或者首先使用USB到TTL转换器，在这种情况下，电压已经处于TTL电平。
以上来自于百度翻译 以下为原文 You're talking about the RS232 voltages. They should NOT be connected to the PIC. You either use a MAX232 style buffer, which transforms the RS232 voltages to TTL voltages, or you use a USB to TTL converter in the first place, in which case the voltages are already at TTL level. |
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