diff --git a/armsrc/iso14443a.c b/armsrc/iso14443a.c
index 17eb156f6..19a79f706 100644
--- a/armsrc/iso14443a.c
+++ b/armsrc/iso14443a.c
@@ -1818,7 +1818,7 @@ static void PrepareDelayedTransfer(uint16_t delay) {
 
     ts->buf[ts->max++] = 0x00;
 
-    for (uint16_t i = 0; i < ts->max; i++) {
+    for (uint32_t i = 0; i < ts->max; i++) {
         uint8_t bits_to_shift = ts->buf[i] & bitmask;
         ts->buf[i] = ts->buf[i] >> delay;
         ts->buf[i] = ts->buf[i] | (bits_shifted << (8 - delay));
@@ -2321,16 +2321,16 @@ void ReaderTransmit(uint8_t *frame, uint16_t len, uint32_t *timing) {
     ReaderTransmitBitsPar(frame, len * 8, par, timing);
 }
 
-static int ReaderReceiveOffset(uint8_t *receivedAnswer, uint16_t offset, uint8_t *par) {
+static uint16_t ReaderReceiveOffset(uint8_t *receivedAnswer, uint16_t offset, uint8_t *par) {
     if (!GetIso14443aAnswerFromTag(receivedAnswer, par, offset))
-        return false;
+        return 0;
     LogTrace(receivedAnswer, Demod.len, Demod.startTime * 16 - DELAY_AIR2ARM_AS_READER, Demod.endTime * 16 - DELAY_AIR2ARM_AS_READER, par, false);
     return Demod.len;
 }
 
-int ReaderReceive(uint8_t *receivedAnswer, uint8_t *par) {
+uint16_t ReaderReceive(uint8_t *receivedAnswer, uint8_t *par) {
     if (!GetIso14443aAnswerFromTag(receivedAnswer, par, 0))
-        return false;
+        return 0;
     LogTrace(receivedAnswer, Demod.len, Demod.startTime * 16 - DELAY_AIR2ARM_AS_READER, Demod.endTime * 16 - DELAY_AIR2ARM_AS_READER, par, false);
     return Demod.len;
 }
@@ -2578,7 +2578,7 @@ int iso14443a_select_cardEx(uint8_t *uid_ptr, iso14a_card_select_t *p_card, uint
                 }
 
                 // finally, add the last bits and BCC of the UID
-                for (uint16_t i = collision_answer_offset; i < Demod.len * 8; i++, uid_resp_bits++) {
+                for (uint32_t i = collision_answer_offset; i < Demod.len * 8; i++, uid_resp_bits++) {
                     uint16_t UIDbit = (resp[i / 8] >> (i % 8)) & 0x01;
                     uid_resp[uid_resp_bits / 8] |= UIDbit << (uid_resp_bits % 8);
                 }
@@ -2972,7 +2972,7 @@ void ReaderIso14443a(PacketCommandNG *c) {
             }
         } else {                    // want to send complete bytes only
             if ((param & ISO14A_TOPAZMODE)) {
-                uint16_t i = 0;
+                size_t i = 0;
                 ReaderTransmitBitsPar(&cmd[i++], 7, NULL, NULL);                        // first byte: 7 bits, no paritiy
                 while (i < len) {
                     ReaderTransmitBitsPar(&cmd[i++], 8, NULL, NULL);                    // following bytes: 8 bits, no paritiy
diff --git a/armsrc/iso14443a.h b/armsrc/iso14443a.h
index 08b73aad2..cf3ecf854 100644
--- a/armsrc/iso14443a.h
+++ b/armsrc/iso14443a.h
@@ -145,7 +145,7 @@ void ReaderIso14443a(PacketCommandNG *c);
 void ReaderTransmit(uint8_t *frame, uint16_t len, uint32_t *timing);
 void ReaderTransmitBitsPar(uint8_t *frame, uint16_t bits, uint8_t *par, uint32_t *timing);
 void ReaderTransmitPar(uint8_t *frame, uint16_t len, uint8_t *par, uint32_t *timing);
-int ReaderReceive(uint8_t *receivedAnswer, uint8_t *par);
+uint16_t ReaderReceive(uint8_t *receivedAnswer, uint8_t *par);
 
 void iso14443a_setup(uint8_t fpga_minor_mode);
 int iso14_apdu(uint8_t *cmd, uint16_t cmd_len, bool send_chaining, void *data, uint8_t *res);
diff --git a/armsrc/mifareutil.c b/armsrc/mifareutil.c
index 0a3008200..ab69dc0a8 100644
--- a/armsrc/mifareutil.c
+++ b/armsrc/mifareutil.c
@@ -76,7 +76,7 @@ uint8_t mf_crypto1_encrypt4bit(struct Crypto1State *pcs, uint8_t data) {
 }
 
 // send X byte basic commands
-int mifare_sendcmd(uint8_t cmd, uint8_t *data, uint8_t data_size, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing) {
+uint16_t mifare_sendcmd(uint8_t cmd, uint8_t *data, uint8_t data_size, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing) {
 
     uint8_t dcmd[data_size + 3];
     dcmd[0] = cmd;
@@ -85,8 +85,8 @@ int mifare_sendcmd(uint8_t cmd, uint8_t *data, uint8_t data_size, uint8_t *answe
 
     AddCrc14A(dcmd, data_size + 1);
     ReaderTransmit(dcmd, sizeof(dcmd), timing);
-    int len = ReaderReceive(answer, answer_parity);
-    if (!len) {
+    uint16_t len = ReaderReceive(answer, answer_parity);
+    if (len == 0) {
         if (g_dbglevel >= DBG_ERROR) Dbprintf("%02X Cmd failed. Card timeout.", cmd);
         len = ReaderReceive(answer, answer_parity);
     }
@@ -94,7 +94,7 @@ int mifare_sendcmd(uint8_t cmd, uint8_t *data, uint8_t data_size, uint8_t *answe
 }
 
 // send 2 byte commands
-int mifare_sendcmd_short(struct Crypto1State *pcs, uint8_t crypted, uint8_t cmd, uint8_t data, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing) {
+uint16_t mifare_sendcmd_short(struct Crypto1State *pcs, uint8_t crypted, uint8_t cmd, uint8_t data, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing) {
     uint16_t pos;
     uint8_t dcmd[4] = {cmd, data, 0x00, 0x00};
     uint8_t ecmd[4] = {0x00, 0x00, 0x00, 0x00};
@@ -113,7 +113,7 @@ int mifare_sendcmd_short(struct Crypto1State *pcs, uint8_t crypted, uint8_t cmd,
         ReaderTransmit(dcmd, sizeof(dcmd), timing);
     }
 
-    int len = ReaderReceive(answer, par);
+    uint16_t len = ReaderReceive(answer, par);
 
     if (answer_parity) *answer_parity = par[0];
 
diff --git a/armsrc/mifareutil.h b/armsrc/mifareutil.h
index bb1360b0e..586672100 100644
--- a/armsrc/mifareutil.h
+++ b/armsrc/mifareutil.h
@@ -66,8 +66,8 @@
 #endif
 
 //functions
-int mifare_sendcmd(uint8_t cmd, uint8_t *data, uint8_t data_size, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing);
-int mifare_sendcmd_short(struct Crypto1State *pcs, uint8_t crypted, uint8_t cmd, uint8_t data, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing);
+uint16_t mifare_sendcmd(uint8_t cmd, uint8_t *data, uint8_t data_size, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing);
+uint16_t mifare_sendcmd_short(struct Crypto1State *pcs, uint8_t crypted, uint8_t cmd, uint8_t data, uint8_t *answer, uint8_t *answer_parity, uint32_t *timing);
 
 // mifare classic
 int mifare_classic_auth(struct Crypto1State *pcs, uint32_t uid, uint8_t blockNo, uint8_t keyType, uint64_t ui64Key, uint8_t isNested);