将收到的 usart uint8_t* 数据与常量字符串进行比较

Question

我正在研究Arduino Due，尝试使用DMA函数，因为我正在处理一个速度至关重要的项目。我发现以下函数可以通过串行接收：

uint8_t DmaSerial::get(uint8_t* bytes, uint8_t length) { 
// Disable receive PDC
uart->UART_PTCR = UART_PTCR_RXTDIS;
// Wait for PDC disable to take effect
while (uart->UART_PTSR & UART_PTSR_RXTEN);
// Modulus needed if RNCR is zero and RPR counts to end of buffer
rx_tail = (uart->UART_RPR - (uint32_t)rx_buffer) % DMA_SERIAL_RX_BUFFER_LENGTH;
// Make sure RPR follows (actually only needed if RRP is counted to the end of buffer and RNCR is zero)
uart->UART_RPR = (uint32_t)rx_buffer + rx_tail;
// Update fill counter
rx_count = DMA_SERIAL_RX_BUFFER_LENGTH - uart->UART_RCR - uart->UART_RNCR;
// No bytes in buffer to retrieve
if (rx_count == 0) { uart->UART_PTCR = UART_PTCR_RXTEN; return 0; } 
uint8_t i = 0;
while (length--) {
bytes[i++] = rx_buffer[rx_head];
// If buffer is wrapped, increment RNCR, else just increment the RCR
if (rx_tail > rx_head) { uart->UART_RNCR++; } else { uart->UART_RCR++; }    
// Increment head and account for wrap around
rx_head = (rx_head + 1) % DMA_SERIAL_RX_BUFFER_LENGTH;
// Decrement counter keeping track of amount data in buffer
rx_count--;
// Buffer is empty
if (rx_count == 0) { break; }
}
// Turn on receiver
uart->UART_PTCR = UART_PTCR_RXTEN;
return i; 
}

因此，据我了解，该函数将接收的内容写入变量字节作为指针，只要不超过长度。所以我这样称呼它：

dma_serial1.get(data, 8);

无需将其返回值分配给变量。我认为收到的值已存储到uint8_t* data但我可能是错的。

最后，我想做的是检查接收到的数据是否是某个字符来做出决定，如下所示：

if (data == "t"){
//do something//}

我怎样才能做到这一点？

Answer 1

为了比较if (data == "t")想要的字符串，你需要一个字符串比较函数，例如strcmp.为此，必须确保参数实际上是(以 0 结尾的(C 字符串：

uint8_t data[9];
uint8_t size = dma_serial1.get(data, 8);
data[size]='';
if (strcmp(data,"t")==0) {
...
}

如果环境中的默认字符类型为signed char，若要将data直接传递给字符串函数，则需要从无符号转换为有符号：

if (strcmp(reinterpret_cast<const char*>(data),"t")==0) {
...
}

因此，完整的MVCE可能如下所示：

int get(uint8_t *data, int size) {
data[0] = 't';
return 1;
}
int main()
{
uint8_t data[9];
uint8_t size = get(data, 8);
data[size]='';
if (strcmp(reinterpret_cast<const char*>(data),"t")==0) {
cout << "found 't'" << endl;
}
}

输出：

found 't'