PC 机 RS485 通讯波特率
我是串行编程的新手。我需要开发一个应用程序，其中设备以 250Kbps 的速度发送需要通过 PC 捕获的串行数据。我知道传统的RS232 COM端口的波特率限制为115Kbaud。
我可以使用RS485转USB转换器来实现这种通信吗？
如果你们中有人熟悉这个主题，还有一个附加问题。 当我使用 C# 获取串行数据时，使用传统的 COM 端口（甚至使用 RS232 到 USB 转换器），当我使用高于 115Kbaud 的值初始化波特率寄存器时，系统会生成异常。
请让我知道需要什么来解决我的高波特率应用。
I am a newbie to serial programming. I need to develop an application where a device send serial data at 250Kbps which needs to be captured through a PC. I know that the conventional RS232 COM ports have a baud rate restriction to 115Kbaud.
Can I use a RS485 to USB converter and achieve this communication?
And an additional questions if any of you guys are familiar with this topic.
When I used C# for acquiring the serial data, with a conventional COM port (or even with a RS232 to USB converter) the system generated exception when I initialized the baud rate register with a value higher than 115Kbaud.
Please let me know what do need to solve my high baud rate application.
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尽管这是一篇旧帖子，但这里有一个包含所有技术细节的答案：
Windows PC RS232 / RS485 应用程序可用的波特率取决于：
RS232/RS485 芯片组及其 Windows 的波特率范围设备驱动程序允许。对于较旧的/消费类设备，这很多时候只包括高达 115200 波特的标准波特率（请参见例如此 来自 NI 的信息）。在原来的帖子中，我认为问题确实是使用了这样一个“基本”RS232 设备，并且其 COM 端口驱动程序本身不接受高于 115200 位的设置。另请注意驱动程序接受的波特率（几乎可以是所有波特率）与 RS232 端的实际传输速率之间的差异。请参阅有关可实现波特率的 FTDI 芯片组知识库。
RS232/RS485接口电气设计的实际限制。知名供应商（MOXA、Lantronix、Digi Edgeport、VSCOM 等）拥有专为工业应用设计的特殊产品和高达 MBit 范围的高波特率。此外，FTDI 本身还提供适用于不同波特率的完整电缆套件。
电缆/连接的电气特性。这包括电缆长度、电缆屏蔽层，对于 RS485 等差分电压传输，还需要使用终端电阻器进行正确的端接（请参阅此 关于 RS485 的 TI 应用说明）。对于 250KBit，我当然建议在两端使用 120 欧姆终端电阻进行适当的端接。
最后 - 在开始自己的编程项目之前，我建议始终使用现有软件工具检查 COM 端口连接。任何免费软件（例如 RealTerm 或 YAT）或我们的 Docklight 评估版 都应该能够执行此操作。
even though this is an old post, here is an answer with all the technical details:
The baud rates available and usable for a Windows PC RS232 / RS485 application depend on:
The baud rate range the RS232/RS485 chipset and its Windows device driver permits. For older/consumer devices, this is many times only include standard baud rates up to 115200 baud (see e.g. this information from NI). In the original post I assume the problem was indeed that such a "basic" RS232 device was used and its COM port driver itself didn't accept a setting setting higher than 115200 bit. Note also the difference between the baud rate the driver accepts (which can be pretty much everything), and the actual transmission rate on the RS232 side. See the FTDI chipset knowledgebase on achievable baud rates.
The actual limits of the electrical design of the RS232/RS485 interface. The known suppliers (MOXA, Lantronix, Digi Edgeport, VSCOM, to name a few) have special products designed for industrial applications and high baud rates up to MBit range. Also FTDI itself offers complete cable sets for different baud rate rates.
The electrical characteristics of your cable / connection. This includes cable length, cable shield, and for differential voltage transmissions like RS485 also proper termination with termination resistors (see e.g. this TI application note on RS485). For 250KBit I'd certainly recommend proper termination with 120 ohms termination resistors on both ends.
Finally - before starting an own programming project, I suggest to always check the COM port connection with an existing software tool. Any freeware like RealTerm or YAT, or our Docklight evaluation should be able to do this.