RS485 & RS232 Example

This example demonstrates RS-485/RS-232 interface communication between an external device and the FlexSense Device. This also demonstrates a basic modem application. Operates as follows:

1. The external device wakes up the module by setting the selected WakeupPin Low.
2. Waits for the "READY\n" string from the FlexSense Device.
3. Sends message string terminated by "\n".
4. Sets the selected WakeupPin High again.
5. The FlexSense Device acknowledges reception with string "\nOK\n".

 
#include <stdio.h>
#include <string.h>
#include "flex.h"
 
#define READY_STRING "READY\n"
#define RECEIVE_TIMEOUT_MS 2000
#define ACK_STRING "\nOK\n"
#define BAUDRATE 115200
 
// Note: Change this to set the desired External Digital IO Pin for Wakeup.
const FLEX_DigitalIOPin WakeupPin = FLEX_EXT_DIGITAL_IO_1;
 
#define USING_RS232 0
#define USING_RS485 1
#define RX_BUFFER_MAX 20
 
#if SERIAL_INTERFACE == USING_RS485
#define SERIAL_PROTOCOL FLEX_SERIAL_PROTOCOL_RS485
#define APPLICATION_NAME "RS485 Example"
 
#elif SERIAL_INTERFACE == USING_RS232
#define SERIAL_PROTOCOL FLEX_SERIAL_PROTOCOL_RS232
#define APPLICATION_NAME "RS232 Example"
 
#else
#error "Must supply a valid 'SERIAL_INTERFACE' to the build!"
#endif
 
// Read new line terminated string from the Serial interface with timeout
// Return number of bytes read or -1 on timeout or string is too long
int ReadStringWithTimeout(uint8_t *Rx, size_t MaxLength) {
  const uint32_t start = FLEX_TickGet();
  size_t count = 0;
  while (FLEX_TickGet() - start < RECEIVE_TIMEOUT_MS) {
    uint8_t ch;
    if (FLEX_SerialRead(&ch, 1) == 1) {
      if (ch == '\n')
        return count;
      Rx[count++] = ch;
      if (count == MaxLength)
        return -1;
    }
  }
  return -1;
}
 
static void Comm() {
  if (FLEX_SerialInit(SERIAL_PROTOCOL, BAUDRATE) != 0) {
    printf("Failed to initialise Serial interface\n");
    return;
  }
  FLEX_SerialWrite((uint8_t *)READY_STRING, strlen(READY_STRING));
 
  uint8_t Rx[RX_BUFFER_MAX] = {0};
  int len = ReadStringWithTimeout(Rx, RX_BUFFER_MAX);
  if (len <= 0) {
    printf("Failed to receive message\n");
  } else {
    FLEX_SerialWrite((uint8_t *)Rx, len);
    FLEX_SerialWrite((uint8_t *)ACK_STRING, strlen(ACK_STRING));
    printf("Received message: ");
    for (int i = 0; i < len; i++)
      printf("%02x", Rx[i]);
    printf("\n");
  }
 
  FLEX_SerialDeinit();
}
 
void FLEX_AppInit() {
  printf("%s\n", APPLICATION_NAME);
 
  // Enabling the Digital IO Wakeup
  FLEX_ExtDigitalIOWakeupModify(WakeupPin, FLEX_EXT_DIGITAL_IO_WAKEUP_ENABLE);
 
  // Registering the Wakeup handler
  FLEX_ExtDigitalIOWakeupHandlerModify(Comm, FLEX_HANDLER_MODIFY_ADD);
}