c-Mikroe RS485点击Azure Sphere-使用RS485发送和接收字节数组

Question

我使用的是连接了RS485点击板的Avnet Azure球体板。在RS485点击中，GPIO PWM变高以从点击板发送RS485信号，而GPIO PWM则变低以接收RS485信号。这里的问题是发送请求至少需要2秒，但在我们将GPIO PWM切换回低电平进行接收之前，连接的传感器会在几毫秒内返回响应。因此，我的UART返回事件没有启动。如有任何帮助，我们将不胜感激。

我的发送UART消息功能

static void SendUartMessage(int uartFd, const char* dataToSend, size_t totalBytesToSend, bool ignoreRx)
{
size_t totalBytesSent = 0;
//size_t totalBytesToSend = strlen(dataToSend);
int sendIterations = 0;
close(r1PinFd);
r1PinFd = GPIO_OpenAsOutput(MIKROE_PWM, GPIO_OutputMode_PushPull, GPIO_Value_High);
while (totalBytesSent < totalBytesToSend) {
sendIterations++;
// Send as much of the remaining data as possible
size_t bytesLeftToSend = totalBytesToSend - totalBytesSent;
const char* remainingMessageToSend = dataToSend + totalBytesSent;
ssize_t bytesSent = write(uartFd, remainingMessageToSend, bytesLeftToSend);
if (bytesSent == -1) {
Log_Debug("ERROR: Could not write to UART: %s (%d).n", strerror(errno), errno);
exitCode = ExitCode_SendMessage_Write;
return;
}
totalBytesSent += (size_t)bytesSent;
}
int c, d;
delay_milliseconds(2000);
close(r1PinFd);
r1PinFd = GPIO_OpenAsOutput(MIKROE_PWM, GPIO_OutputMode_PushPull, GPIO_Value_Low);
Log_Debug("Sent %zu bytes over UART in %d calls.n", totalBytesSent, sendIterations);
}

我的RS485 UART返回事件

static void UartEventHandler(EventLoop* el, int fd, EventLoop_IoEvents events, void* context)
{
const size_t receiveBufferSize = 256;
uint8_t receiveBuffer[receiveBufferSize + 1]; // allow extra byte for string termination
ssize_t bytesRead;
// Read incoming UART data. It is expected behavior that messages may be received in multiple
// partial chunks.
bytesRead = read(uartFd, receiveBuffer, receiveBufferSize);
if (bytesRead == -1) {
Log_Debug("ERROR: Could not read UART: %s (%d).n", strerror(errno), errno);
exitCode = ExitCode_UartEvent_Read;
return;
}
if (bytesRead > 0) {
receiveBuffer[bytesRead] = 0;
Log_Debug("UART received %d bytes: '%s'.n", bytesRead);
char  data_hex_str[sizeof(receiveBuffer) / sizeof(receiveBuffer[0])];
get_hex(receiveBuffer, sizeof(receiveBuffer) / sizeof(receiveBuffer[0]), data_hex_str, sizeof(receiveBuffer) / sizeof(receiveBuffer[0]), 16);
strcat(returnDataUart, data_hex_str);
Log_Debug("s", returnDataUart);
}
char* pjsonBuffer = (char*)malloc(JSON_BUFFER_SIZE);
if (pjsonBuffer == NULL) {
Log_Debug("ERROR: not enough memory to send telemetry");
}
snprintf(pjsonBuffer, JSON_BUFFER_SIZE,
"{"gX":%.2lf, "gY":%.2lf, "gZ":%.2lf, "aX": %.2f, "aY": "
"%.2f, "aZ": %.2f, "pressure": %.2f, "light_intensity": %.2f, "
""altitude": %.2f, "temp": %.2f,  "rssi": %d, "RS485": %s}",
acceleration_g.x, acceleration_g.y, acceleration_g.z, angular_rate_dps.x,
angular_rate_dps.y, angular_rate_dps.z, pressure_kPa, light_sensor, altitude,
lsm6dso_temperature, network_data.rssi, returnDataUart);
Log_Debug("n[Info] Sending telemetry: %sn", pjsonBuffer);
SendTelemetry(pjsonBuffer, true);
free(pjsonBuffer);
}

Answer 1

RS485是半双工的，因此一次只能传输一个设备。因此，您必须在发送完数据后立即关闭变送器。理想情况下，您应该在硬件中执行此操作。在您的情况下，在关闭发射器之前，看起来您有一个delay_milliseconds(2000);。这会导致冲突，并且传输的任何数据都将丢失。