nfc-anticol now works even after running another program that change the modulation (Fixes Issue 111) (Thanks to Phil for help).

examples/nfc-anticol.c

@@ -167,6 +167,11 @@ main (int argc, char *argv[])
     nfc_perror (pnd, "nfc_configure");
     exit (EXIT_FAILURE);
   }
+  // Force 14443-A mode
+  if (!nfc_configure (pnd, NDO_FORCE_ISO14443_A, true)) {
+    nfc_perror (pnd, "nfc_configure");
+    exit (EXIT_FAILURE);
+  }
 
   // Enable field so more power consuming cards can power themselves up
   if (!nfc_configure (pnd, NDO_ACTIVATE_FIELD, true)) {

include/nfc/nfc-types.h

@@ -162,6 +162,8 @@ typedef enum {
   NDO_AUTO_ISO14443_4 = 0x40,
 /** Use automatic frames encapsulation and chaining. */
   NDO_EASY_FRAMING = 0x41,
+/** Force the chip to switch in ISO14443-A */
+  NDO_FORCE_ISO14443_A = 0x42,
 } nfc_device_option_t;
 
 ////////////////////////////////////////////////////////////////////

libnfc/chips/pn53x.c

@@ -708,12 +708,26 @@ pn53x_configure (nfc_device_t * pnd, const nfc_device_option_t ndo, const bool b
   case NDO_AUTO_ISO14443_4:
     // TODO: PN53x parameters could not be read, so we have to buffered current value in order to prevent from configuration overwrite
     // ATM, buffered current value is not needed due to a single usage of these parameters
-    btValue =
+    btValue = (bEnable) ? (SYMBOL_PARAM_fAutomaticRATS | SYMBOL_PARAM_fAutomaticATR_RES) : SYMBOL_PARAM_fAutomaticATR_RES;
-      (bEnable) ? (SYMBOL_PARAM_fAutomaticRATS | SYMBOL_PARAM_fAutomaticATR_RES) : SYMBOL_PARAM_fAutomaticATR_RES;
     if (!pn53x_set_parameters (pnd, btValue))
       return false;
     return true;
     break;
+
+  case NDO_FORCE_ISO14443_A:
+    if(!bEnable) {
+      // Nothing to do
+      return true;
+    }
+    // Force pn53x to be in ISO1444-A mode
+    if (!pn53x_set_reg (pnd, REG_CIU_TX_MODE, SYMBOL_TX_FRAMING, 0x00)) {
+      return false;
+    }
+    if (!pn53x_set_reg (pnd, REG_CIU_RX_MODE, SYMBOL_RX_FRAMING, 0x00)) {
+      return false;
+    }
+    return true;
+    break;
   }
 
   // When we reach this, the configuration is completed and succesful

libnfc/chips/pn53x.h

@@ -32,21 +32,35 @@
 // Registers and symbols masks used to covers parts within a register
 #  define REG_CIU_TX_MODE           0x6302
 #  define SYMBOL_TX_CRC_ENABLE      0x80
+// TX_FRAMING bits explanation:
+//   00 : ISO/IEC 14443A/MIFARE and Passive Communication mode 106 kbit/s
+//   01 : Active Communication mode
+//   10 : FeliCa and Passive Communication mode at 212 kbit/s and 424 kbit/s
+//   11 : ISO/IEC 14443B
+#  define SYMBOL_TX_FRAMING         0x03
+
 #  define REG_CIU_RX_MODE           0x6303
 #  define SYMBOL_RX_CRC_ENABLE      0x80
 #  define SYMBOL_RX_NO_ERROR        0x08
 #  define SYMBOL_RX_MULTIPLE        0x04
+// RX_FRAMING follow same scheme than TX_FRAMING
+#  define SYMBOL_RX_FRAMING         0x03
+
 #  define REG_CIU_TX_AUTO           0x6305
 #  define SYMBOL_FORCE_100_ASK      0x40
 #  define SYMBOL_AUTO_WAKE_UP       0x20
 #  define SYMBOL_INITIAL_RF_ON      0x04
+
 #  define REG_CIU_MANUAL_RCV        0x630D
 #  define SYMBOL_PARITY_DISABLE     0x10
+
 #  define REG_CIU_STATUS2           0x6338
 #  define SYMBOL_MF_CRYPTO1_ON      0x08
+
 #  define REG_CIU_CONTROL           0x633C
 #  define SYMBOL_INITIATOR          0x10
 #  define SYMBOL_RX_LAST_BITS       0x07
+
 #  define REG_CIU_BIT_FRAMING       0x633D
 #  define SYMBOL_TX_LAST_BITS       0x07