drivers: UART based drivers could now use uart_flush_input() to discard junk bytes on input.

libnfc/buses/uart.h

@@ -42,6 +42,7 @@ typedef void *serial_port;
 
 serial_port uart_open (const char *pcPortName);
 void    uart_close (const serial_port sp);
+void    uart_flush_input (const serial_port sp);
 
 void    uart_set_speed (serial_port sp, const uint32_t uiPortSpeed);
 uint32_t uart_get_speed (const serial_port sp);

libnfc/buses/uart_posix.c

@@ -100,9 +100,6 @@ uart_open (const char *pcPortName)
   sp->tiNew.c_cc[VMIN] = 0;     // block until n bytes are received
   sp->tiNew.c_cc[VTIME] = 0;    // block until a timer expires (n * 100 mSec.)
 
-  // This line seems to produce absolutely no effect on my system (GNU/Linux 2.6.35)
-  tcflush (sp->fd, TCIFLUSH);
-
   if (tcsetattr (sp->fd, TCSANOW, &sp->tiNew) == -1) {
     uart_close (sp);
     return INVALID_SERIAL_PORT;
@@ -110,6 +107,29 @@ uart_open (const char *pcPortName)
   return sp;
 }
 
+void
+uart_flush_input (serial_port sp)
+{
+  // This line seems to produce absolutely no effect on my system (GNU/Linux 2.6.35)
+  tcflush (((serial_port_unix *) sp)->fd, TCIFLUSH);
+  // So, I wrote this byte-eater
+  // Retrieve the count of the incoming bytes
+  int available_bytes_count = 0;
+  int res;
+  res = ioctl (((serial_port_unix *) sp)->fd, FIONREAD, &available_bytes_count);
+  if (res != 0) {
+    return;
+  }
+  if (available_bytes_count == 0) {
+    return;
+  }
+  char* rx = malloc (available_bytes_count);
+  // There is something available, read the data
+  res = read (((serial_port_unix *) sp)->fd, rx, available_bytes_count);
+  DBG ("%d bytes have eatten.", available_bytes_count);
+  free (rx);
+}
+
 void
 uart_set_speed (serial_port sp, const uint32_t uiPortSpeed)
 {

libnfc/buses/uart_win32.c

@@ -87,6 +87,12 @@ uart_close (const serial_port sp)
   free (sp);
 }
 
+void
+uart_flush_input (const serial_port sp)
+{
+  // TODO: Implement me
+}
+
 void
 uart_set_speed (serial_port sp, const uint32_t uiPortSpeed)
 {

libnfc/drivers/arygon.c

@@ -111,6 +111,8 @@ arygon_probe (nfc_device_desc_t pnddDevices[], size_t szDevices, size_t * pszDev
     DBG ("Trying to find ARYGON device on serial port: %s at %d bauds.", pcPort, ARYGON_DEFAULT_SPEED);
 
     if ((sp != INVALID_SERIAL_PORT) && (sp != CLAIMED_SERIAL_PORT)) {
+      // We need to flush input to be sure first reply does not comes from older byte transceive
+      uart_flush_input (sp);
       uart_set_speed (sp, ARYGON_DEFAULT_SPEED);
 
       nfc_device_t *pnd = nfc_device_new ();
@@ -167,6 +169,8 @@ arygon_connect (const nfc_device_desc_t * pndd)
   if ((sp == CLAIMED_SERIAL_PORT) || (sp == INVALID_SERIAL_PORT))
     return NULL;
 
+  // We need to flush input to be sure first reply does not comes from older byte transceive
+  uart_flush_input (sp);
   uart_set_speed (sp, pndd->uiSpeed);
 
   // We have a connection
@@ -231,6 +235,9 @@ arygon_disconnect (nfc_device_t * pnd)
 bool
 arygon_tama_send (nfc_device_t * pnd, const byte_t * pbtData, const size_t szData)
 {
+  // Before sending anything, we need to discard from any junk bytes
+  uart_flush_input (DRIVER_DATA(pnd)->port);
+
   byte_t abtFrame[ARYGON_TX_BUFFER_LEN] = { DEV_ARYGON_PROTOCOL_TAMA, 0x00, 0x00, 0xff };     // Every packet must start with "0x32 0x00 0x00 0xff"
 
   size_t szFrame = 0;

libnfc/drivers/pn532_uart.c

@@ -90,6 +90,8 @@ pn532_uart_probe (nfc_device_desc_t pnddDevices[], size_t szDevices, size_t * ps
     DBG ("Trying to find PN532 device on serial port: %s at %d bauds.", pcPort, PN532_UART_DEFAULT_SPEED);
 
     if ((sp != INVALID_SERIAL_PORT) && (sp != CLAIMED_SERIAL_PORT)) {
+      // We need to flush input to be sure first reply does not comes from older byte transceive
+      uart_flush_input (sp);
       // Serial port claimed but we need to check if a PN532_UART is connected.
       uart_set_speed (sp, PN532_UART_DEFAULT_SPEED);
 
@@ -154,6 +156,8 @@ pn532_uart_connect (const nfc_device_desc_t * pndd)
   if ((sp == CLAIMED_SERIAL_PORT) || (sp == INVALID_SERIAL_PORT))
     return NULL;
 
+  // We need to flush input to be sure first reply does not comes from older byte transceive
+  uart_flush_input (sp);
   uart_set_speed (sp, pndd->uiSpeed);
 
   // We have a connection
@@ -219,6 +223,9 @@ pn532_uart_wakeup (nfc_device_t * pnd)
 bool
 pn532_uart_send (nfc_device_t * pnd, const byte_t * pbtData, const size_t szData)
 {
+  // Before sending anything, we need to discard from any junk bytes
+  uart_flush_input (DRIVER_DATA(pnd)->port);
+
   switch (CHIP_DATA(pnd)->power_mode) {
     case LOWVBAT: {
       /** PN532C106 wakeup. */