英文:
Serial port - receive bytes count
问题
我从stm32传输了256字节，然后在Visual Studio中通过SerialPort接收。为什么我接收到了2次字节？首先是32，然后是224。
stm32 USART配置：
huart2.Instance = USART2;
huart2.Init.BaudRate = 9600;
huart2.Init.WordLength = UART_WORDLENGTH_8B;
huart2.Init.StopBits = UART_STOPBITS_1;
huart2.Init.Parity = UART_PARITY_NONE;
huart2.Init.Mode = UART_MODE_TX_RX;
huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart2.Init.OverSampling = UART_OVERSAMPLING_16;
huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart2.Init.ClockPrescaler = UART_PRESCALER_DIV1;
huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
uint8_t memory[256];
for (int i = 0; i < 256; i++)
memory[i] = 0xFF;
HAL_UART_Transmit(&huart2, memory, sizeof(memory), HAL_MAX_DELAY);
Visual Studio：
private void readerSerialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
if (!this.readerSerialPort.IsOpen) return;
int bytes = this.readerSerialPort.BytesToRead;
byte[] buffer = new byte[bytes];
this.readerSerialPort.Read(buffer, 0, bytes);
MessageBox.Show(buffer.Length.ToString());
}
为什么会发生这种情况？
英文:
I transmit 256 bytes from stm32 and receive it by SerialPort in Visual studio. Why i receive bytes 2 times? 32 and then 224.
stm32 USART configuration:
huart2.Instance = USART2;
huart2.Init.BaudRate = 9600;
huart2.Init.WordLength = UART_WORDLENGTH_8B;
huart2.Init.StopBits = UART_STOPBITS_1;
huart2.Init.Parity = UART_PARITY_NONE;
huart2.Init.Mode = UART_MODE_TX_RX;
huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart2.Init.OverSampling = UART_OVERSAMPLING_16;
huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart2.Init.ClockPrescaler = UART_PRESCALER_DIV1;
huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
uint8_t memory[256];
for (int i = 0; i < 256; i++)
memory[i] = 0xFF;
HAL_UART_Transmit(&huart2, memory, sizeof(memory), HAL_MAX_DELAY);
Visual studio:
private void readerSerialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
if (!this.readerSerialPort.IsOpen) return;
int bytes = this.readerSerialPort.BytesToRead;
byte[] buffer = new byte[bytes];
this.readerSerialPort.Read(buffer, 0, bytes);
MessageBox.Show(buffer.Length.ToString());
}
Why is this happening?
答案1
得分: 2
串行协议以及USB大容量端点，这些很可能在微控制器和您的计算机之间使用，都是流协议。它们假定字节的流是恒定的，不使用定界符来传输原始数据块的边界。
这与传输和保留独立数据块的面向消息的协议相对立。
因此，您用于提交数据的块的大小不会被保留。多个块可能会被合并成一个单一的块，一个单一的块也可能会被分割成多个块，就像您所经历的那样。
如果您需要面向消息的协议，您需要在流协议的基础上自行实现它。典型的方法包括：
- 定义一个带有消息长度的消息头的消息结构。
- 使用定界符（如果传输文本数据，最简单的情况下使用CR/LF）。
英文:
The serial protocol as well as USB bulk endpoints, which are likely used between the microcontroller and your PC are stream protocols. They assume a constant flow of bytes and do not use delimiters to transmit the boundaries of the original data chunks.
This is opposed to message-oriented protocol that transmit and retain distinct chunks of data.
As a consequence, the size of the chunks you used to submit the data are not retained. Multiple chunks might be joined into a single one, and a single chunk might be split into multiple ones as you have experienced.
If you require a message-oriented protocol, you need to implemented it yourself on top of the stream protocol. Typical approaches are:
- Define a message structure with a message header containing the message length.
- Use delimiters (CR/LF in the simplest case if text data is transmitted).
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